Optical transmission equipment which transmits an amplified optical data signal and an optical surveillance signal

Abstract
An optical transmission system accomplishes optical transmission over a long distance by combining a multiplexing line terminal with optical amplifiers, linear repeaters, and regenerators with optical amplifiers combined together. The system also accomplishes the optical transmission over a short distance by directly connecting the linear terminals therebetween, with an electric-to-optic converter replaced by an electric-to-optic converter having a semiconductor amplifier, with an optic-to-electric converter by an optic-to-electric converter having an avalanche photodiode as light receiver, and with no use of any optical booster amplifier and optical preamplifier in the multiplexing line terminal. With these, the optical transmission system can be easily constructed depending on the transmission distance required.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to an optical transmission method and system for carrying data transmission with the use of optical fiber. More particularly, it concerns an optical transmission method and system preferable in high-speed data transmission over a long distance.




2. Description of the Related Art




Art related to the optical transmission system includes, for example, the technique disclosed in the Japanese Patent Application Laid-Open 3-296334.




However, it is required to accomplish an optical transmission System operating at higher speeds since development of the modern information society has increased long-distance communication traffic in recent years. Also, it is desired that the optical transmission system can transmit data even longer distances without repeaters to increase reliability and decrease cost of the system.




Furthermore, the number of fields to which an optical transmission system is applied has been increased with the recent development of the information society. For this reason, it is needed to achieve an optical transmission system having a variety of functions and the capacities to satisfy various requirements.




SUMMARY OF THE INVENTION




In view of the foregoing, it is an object of the present invention to provide an optical transmission system constructing method capable of easily constructing an optical transmission method and system depending on required functions and capacities.




Briefly, the foregoing object is accomplished in accordance with aspects of the present invention by an optical transmission system. The optical transmission system is characterized by constructing a line terminal having multiplexing means for multiplexing signals and demultiplexing means for demultiplexing the multiplexed signal to serve as a transmitter. The line terminal is selectively capable of implementing either of two types of converters a first combination of an electric-to-optic converter circuit for converting the electric signal multiplexed by the multiplexing means to a transmission light with an optical fiber amplifier for amplifying the transmitting light before feeding into an optical transmission medium; or an electric-to-optic converting means having a semiconductor optical amplifier for converting the electric signal multiplexed by the multiplexing means to a transmission light before feeding an optical transmission line. The optical transmission system also is characterized by constructing the line terminal to serve as a receiver. The line terminal is selectively capable of implementing either; a second combination of an optical fiber amplifier for amplifying a receiving light from an optical transmission medium with an optic-to-electric converter circuit for converting the amplified receiving light to an electric signal before feeding to the demultiplexing means; or an optic-to-electric converting means for converting the received light from the optical transmission medium to an electric signal before feeding to the demultiplexing means with an avalanche photodiode used as a light receiver.




Also, the optical transmission system is characterized in constructing the optical transmission system for use as a long distance optical transmission system; A plurality of the line terminals having the first combination to serve as the transmitter and the second combination to serve as the receiver implemented therein; each are connected to the optical transmission medium through a single or a plurality of repeaters inserted in the optical transmission medium for multiplying the optical light signal on the optical transmission medium.




Further, the optical transmission system is characterized in constructing the optical transmission system for use as a short distance optical transmission system; The plurality of the line terminals having the electric-to-optic converting means having a semiconductor optical amplifier therein to serve as the transmitter and the optic-to-electric converting means having the avalanche photodiode used as the light receiver to serve as the receiver implemented therein; are each directly connected to the optical transmission line.




The optical transmission system constructing method of the present invention enables an easy construction of any of the long-distance and short-distance optical transmission systems only by selecting desired types of transmitters and receivers to be implemented to change the combinations of the units. This is because the line terminal is constructed to serve as the transmitter; The line terminal is selectively capable of implementing either the first combination of an electric-to-optic converter circuit for converting the electric signal multiplexed by the multiplexing means to the transmission light with an optical fiber amplifier for amplifying the transmitting light before feeding into an optical transmission medium or electric-to-optic converting means having the semiconductor optical amplifier for converting the electric signal multiplexed by the multiplexing means to the transmission light before feeding an optical transmission line, and that to serve as the receiver, the line terminal is selectively capable of implementing either the second combination of an optical fiber amplifier for amplifying the receiving light from an optical transmission medium with an optic-to-electric converter circuit for converting the amplified receiving light to electric signal before feeding to the demultiplexing means or an optic-to-electric converting means for converting the received light from the optical transmission medium to electric signal before feeding to the demultiplexing means with an avalanche photodiode used as light receiver.




The foregoing and other objects, advantages, manner of operation and novel features of the present invention will be understood from the Following detailed description when read in connection with the accompanying drawings.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a block diagram for a functional construction of an optical transmission system of an embodiment of the present invention.





FIG. 2

is an overall configuration for a network system related to the embodiment of FIG.


1


.





FIG. 3

is a configuration for a network among large-scale switching nodes extracted from the network system of FIG.


2


.





FIG. 4

is a configuration for a network among small-scale switching nodes and among small-scale switching nodes and the large scale switching node extracted from the network system.





FIG. 5

is a configuration for a network for a metropolitan area extracted from the network system.





FIG. 6

is block diagrams for a functional construction of a node.





FIG. 7

is a hierarchical construction of a network system.





FIG. 8

is a frame construction for a multiplexing frame used in the network system.





FIG. 9

is logical positions of path groups.





FIG. 10

is a bit allocation of overhead of the path groups.





FIG. 11

is an example of setting the path group in a ring.





FIG. 12

shows path group switching procedures at failure.





FIG. 13

shows a typical sequence of switching requests.





FIG. 14

is a block diagram for a configuration of the network system related to the embodiment.





FIG. 15

is a sequence diagram for transfer of alarms in the network system.





FIG. 16

is a block diagram for the optical transmission system for a long distance system.





FIG. 17

is a block diagram for the optical transmission system for a short distance system.





FIG. 18

is a block diagram for a clock transit system for the optical transmission system.





FIG. 19

is bytes to be scrambled of an overhead in a STM-64 section.





FIG. 20

is a block diagram for the 1R-REP.





FIG. 21

is a block diagram for a board construction of the 1R-REP.





FIG. 22

is a format for a surveillance and control signal for use in the surveillance and control of the 1R-REP.





FIG. 23

is a block diagram for an inter-office transmission line interface of the LT-MUX.





FIG. 24

is a block diagram for the intra-office transmission line interface of the LT-MUX.





FIG. 25

is a relationship of multiplex and demultiplex between a STM-64 frame and a STM-1×64 supported by the LT-MUX.





FIG. 26

is a block diagram for a transmitter of the LT-MUX forming the long distance system.





FIG. 27

is a block diagram for the transmitter of the LT-MUX forming the short distance system.





FIG. 28

is a block diagram for a receiver of the LT-MUX forming the long distance system.





FIG. 29

is a block diagram for the receiver of the LT-MUX forming the short distance system.





FIG. 30

is a block diagram for a node having LT-MUXes and an ADM switch used.





FIG. 31

is a block diagram for extracted parts serving as the surveillance and control system for the LT-MUX.





FIG. 32

lists features of the functional blocks of the surveillance and control system.





FIG. 33

is a block diagram for a redundancy configuration of a transmitting system in the LT-MUX.





FIG. 34

is a block diagram for the redundancy configuration of a receiving system in the LT-MUX.





FIG. 35

is a block diagram for construction of a hitless switching process feature section for transmission line.





FIG. 36

is a block diagram for a construction of a 3R-REP.





FIG. 37

is a front view for an implementation of the 1R-REP.





FIG. 38

represents structures of an optical preamplifier and optical booster amplifier forming a single 1R-REP system.





FIG. 39

is a front view for an implementation of the LT-MUX.





FIG. 40

is a front view for an implementation of two systems of the LT-MUX in a single rack without the line redundancy configuration.





FIG. 41

is a front view for an implementation of the LT-MUX for constructing the small scale switching node with a 40G switch unit built in as shown in

FIG. 6



b.







FIG. 42

is a structural view for a 40G switch.





FIG. 43

is a front view of an implementation of the LT-MUX for constructing the large scale switching node.





FIG. 44

is a front view of an implementation of the 3R-REP.











DETAILED DESCRIPTION




The following describes an embodiment according to the present invention for the optical transmission system by reference to the accompanying drawings.




1. General Description




First, this section outlines the optical transmission system of the embodiment.





FIG. 1

is a block diagram for the functional construction of the optical transmission system of the embodiment.




The optical transmission system, as shown in

FIG. 1



a


, is an ultra-long distance transmission system for making optical transmission between line terminals with multiplexers (hereinafter referred to as the LT-MUX


1


) or between the LT-MUX


1


and a regenerator (hereinafter referred to as the 3R-REP


3


) with use of an optical amplifier repeater (hereinafter referred to as the 1R-REP


2


). The system can send the data at 10 Gb/sec through an optical fiber


40


up to 320 km by the 3R-REP


3


at the longest intervals of 80 km by the 1R-REP


2


.




The LT-MUX


1


makes a multiplex and section-termination-process (


12


) of the data received by an intra-office interface


11


provided therein, and converts them to an optical signal (


13


). An optical booster amplifier


14


magnifies the optical signal before feeding it into an optical transmission medium. On the other hand, the data received from the optical transmission medium is magnified by an optical pre-amplifier


15


before being converted to an electrical signal (


16


). The signal then is demultiplexed and section-termination-processed (


12


) before being distributed to the intra-office interfaces


11


. The 1R-REP


2


repeats the optical signal in a way that any of the optical fiber amplifiers


21


and


22


magnifies the optical signal received from the optical transmission medium before feeding it out. The 3R-REP


3


regenerates the data to repeat in a way that the data received from the optical transmission medium are magnified by an optical pre-amplifier


35


before being converted to electrical signal (


36


). The electrical signal then is demultiplexed and section-termination-processed (


32


) and is multiplexed and section-termination-processed (


32


) again. It further is converted to optical signal (


33


) and magnified by an optical booster amplifier


34


before being fed into the optical transmission medium.




The interface of any equipment with the optical transmission medium (hereinafter referred to as the inter-office interface) is equivalent to the CCITT recommended synchronous transport modulelevel N (STM−N) where N=64, and uses a scrambled binary NRZ (non-return to zero) as transmission line code. A spectrum broading is used to prevent a stimulated Brillouin scattering due to a higher power output.




The intra-office interface


11


of the LT-MUX


1


can contain a series of STM-1 (150 Mb/sec) by 64 or a series of STM-4 (600 Mb/sec) by 16. (Note that the series of STM-4 (600 Mb/sec) by 1 can be compatible with the series of STM-1 by 4).




The optical transmission system can be configured in another way so that instead of the 1R-REP


2


shown in

FIG. 1



a


, the LT-MUXes


1


are directly connected together or the LT-MUX


1


is directly connected with the 3R-REP


3


. In this case, the transmission distance is up to 120 km without repeater.




Also, the optical transmission system can be configured in still another way such as that shown in

FIG. 1



b


; The 1R-REP


2


, the optical booster amplifier


14


, and the optical pre-amplifier


15


are omitted, but LT-MUXes


1


having an opto-electric converter


2010


and an electro-optic converter


2000


which are different in the characteristics from those of the LT-MUX


1


in

FIG. 1



a


are directly connected together. In this case, the output level is around +6 dBm, and the transmission distance is up to 80 km without repeater.




The optical transmission system having the LT-MUX


1


, the 3R-REP


3


, the optical booster amplifier


14


, and optical pre-amplifier


15


is called the long-distance system hereunder; and the optical transmission system having no optical booster amplifier


14


and optical pre-amplifier


15


in the LT-MUX


1


and 3R-REP


3


is called the short distance system hereunder.




2. Overall System Configuration




In turn, this section describes a network system having the optical transmission system of the embodiment.





FIG. 2

is an overall configuration for a network system related to the embodiment.




In the figure are indicated a large scale switching node


110


having the LT-MUX


1


of the embodiment and a small scale switching node


120


having the LT-MUX


1


of the embodiment.




The large-scale switching nodes


110


in the network system related to the embodiment, as shown in the figure, are directly connected therebetween in a ladder-shaped structure with use of the 1R-REP


2


and the 3R-REP


3


. The network system has routes diversed therein and the CCITT recommended VC-3/4 path protection switch in the meshed network, thereby increasing reliability of the network. The small-scale switching nodes


120


are ring-structured, and the small-scale switching nodes


120


and the large scale switching nodes


110


are also ring-structured. This not only provides a multiplexing effect that allows efficient use of the large-capacity transmission medium, but also keeps two routes that can increase the reliability. In addition, a metropolitan area


130


has a multiplicity of rings for increasing the reliability in a relatively narrow, but large, traffic area extending over a flat wide area.





FIG. 3

is a configuration for a network among the large-scale switching nodes


110


extracted from the network system.




The large-scale switching nodes


110


, as shown in the figure, are directly connected there among with use of the 1R-REPs


2


and the 3R-REPs


3


without switching through an intermediate node, thereby decreasing the line cost. A distance between the 1R-REPs


2


is designed up to 80 km taking into account the S/N ratio, and the distance between one of the 3RREPs


3


and the node is designed up to 320 km in consideration of the nonlinear distortion of the optical fiber.





FIG. 4

is a configuration for a network among the small-scale switching nodes


120


and among the small-scale switching nodes


120


and the large scale switching nodes


110


extracted from the network system.




If a distance between the small-scale switching nodes


120


is shorter than 120 km, as shown in the figure, no repeaters are used, and instead direct connection is made between any two of the smallscale switching nodes


120


. If the distance exceeds 120 km, the 1R-REP


2


is used to make the long distance system as mentioned previously. If the distance is shorter than 80 km, as will be described in detail later, the 10 Gb/sec transmitter is replaced by the one made up of a semiconductor optical amplifier and an APD (avalanche photodiode) to form a further economical short distance system (

FIG. 1



b


).





FIG. 5

is a configuration for a network for the metropolitan area extracted from the network system.




The metropolitan area, as shown in the figure, has a plurality of adjoining rings formed by the transmission media connecting the nodes in a meshed network, thereby accomplishing efficient multiplex operation and high reliability. It should be noted that there will be a greater number of the shorter node distances than 80 km. Then, as described above, the short distance system is made up of the semiconductor optical amplifier and the APD to form the network at low cost.





FIG. 6

is block diagrams for the functional construction of the node.




The large scale switching node


110


, as shown in

FIG. 6



a


, has two LT-MUXes


1


and a VC-3/4 cross-connection switch


111


for path switching and setting at the VC-3/4 level in the synchronous digital hierarchy (SDH). The two LT-MUXes


1


are connected by a high-speed interface which will be described later, but not any intra-office interface. The large scale switching node


110


also has the STM-1 interface and the STM-4 interface as the intra-office interfaces. These interfaces can connect a line repeater terminal


5000


for transmission between a 600 Mb/sec or 2.4 Gb/sec offices, a cross-connection equipment


5100


for terminating the intra-office interface


11


, and an ATM cross-connection switch


5200


. The ATM cross-connection switch


5200


, if used, can accomplish lower cost and decrease cell delay as the 600 Mb/sec intra-office interface is used. Note that the large scale switching node


110


can be alternatively made up of the two LTMUXes


1


and a cross-connect equipment


111


.




The small scale switching node


120


is the same as the large scale switching node


110


or as shown in

FIG. 1



b


, has the LT-MUX


1


and a VC-3/4 add-drop multiplex (ADM) switch. The small scale switching node


120


also, like the large scale switching node


110


, has the STM-1 interface and the STM-4 interface as the intra-office interfaces, which can connect the line repeater terminal


5000


for transmission between a 600 Mb/sec or 2.4 Gb/sec offices, the cross-connection equipment


5100


for terminating the intra-office interface


11


, and the ATM cross-connection switch


5200


.




The intra-office interface


11


of the LT-MUX


1


is used for the STM-1 interface and the STM-4 interface for each node.




Table 1 shows a hierarchy of the network system and terminals at the respective hierarchy level.















TABLE 1












OVER-






NO.




LEVEL




TERMINAL




HEAD











1




VC-¾




VC-½ processors, and




VC-¾ POH








ATM unit






2




VC-¾ path




VC-¾ cross-connector




z3 byte of







group




(virtual ring branch -




representing







(VC-¾ PG)




insertion point)




VC-¾ POH






3




STM-64




LT-MUX




MSOH







Section






4




Regenerator




3R-REP and LT-MUX




RSOH







section






5




Linear repeater




1R-REP, 3R-REP, LT-MUX




Wavelength







section





multiplexed









management









signal














As shown in the table, the present embodiment defines the new VC3/4 path group to accomplish easy path switching upon failure of any transmission medium.





FIG. 8

is a frame construction for an STM-64 which is an inter-office interface.




The overhead for the VC-3/4 path group, as shown in the figure, is the Z3 byte of the representing VC-3/4 POH forming the VC-3/4 path group.




The following describes the path switching with use of the path group at failure of any transmission medium.




The term “path group” as used herein denotes a set of parts within a ring of the VC-3/4 path such that a point of insertion into a virtual ring and a point of branch from the virtual ring is equal to each other. The term “virtual ring” as used herein denotes a ring extracted from the network as a part which can virtually form a ring-like path. It should be noted that as shown in

FIG. 9

, the path group is positioned between section and plane path layer in view of the network layer structure.




The embodiment switches the path group when the path croup is at failure. The path group is managed with use of the Z3 byte of the representing VC-3/4 path overhead within the path group.

FIG. 10

is a bit allocation of the Z3 byte. The path group failure is detected by a path group alarm indication signal (PGAIS) defined in Z3 byte.




Table 2 shows path switching features in the embodiment.














TABLE 2









NO.




ITEM




DESCRIPTION











1




Switching unit




VC-¾ path group (set of VC-¾ paths








in same route within ring)






2




Switching network




Virtual ring (on VC-¾ path mesh)







topology






3




Protection form




1 + 1 bidirectional switching (Working








path group and protection group are








turned reversely on ring.)






4




Switching control




Autonomous switching to ground office







method




in ring by APS control for path group






5




APS byte




b1 to b4 of z3 byte path group








representing VC-¾






6




APS protocol




Conform to 1 + 1 switching protocol of








section APS






7




Switching trigger




Path group AIS reception at path group








terminal point








(Path group AIS bit in z4 type = 1)






8




Switching




VC-¾ cross-connection switch







equipment




(LT-MUX with XC and LT-MUX with








ADM)






9




Switch control




Switching ACM* meshed network







method




in units of VC.











*ACM address control memory which is a memory for controlling switches in cross-connection unit and the like.













As shown in Table 2 above, the embodiment uses an alternative meshed network switching to increase reliability. Controlling the mesh switching in the embodiment is the autonomous switching in units of the VC-3/4 path group virtual ring, which conforms to the section APS recommended by CCITT.





FIG. 11

is an example of setting the path group in the ring. The protection path group is extended in the direction reverse to the working one.





FIG. 12

is path group switching procedures at failure.

FIG. 13

is a typical sequence of switching requests. The switching sequence, as shown in

FIG. 13

, conforms to the usual 1+1 section APS. Finally, Table 3 shows priorities of the switching requests and coding of the Z3 byte, and Table 4 shows coding of the path group status.















TABLE 3










TYPE OF





z3 BYTE






PRIOR-




SWITCHING





b1, b2,






ITY




REQUEST




DESCRIPTION




b3, b4











1




Lockout




Inhibit all switchings by any













of following switching








requests, with working state








held.






2




Forced switching




Make switching if protection




1 1 1 0







(FS)




path group is normal.






3




Signal failure




Make switching if protection




1 1 0 0







(SF)




path group is normal after








results of surveillance of








working path group AIS and








units are triggered for








failure. Path group AIS is








generated by LOS, LOF, and








severed MER.






4




Manual switching




Make switching if protection




1 0 0 0








path group is normal.






5




Wait to restore




Do not release from switched




0 1 1 0








state during the waiting








period even if the working








path group is restored








while the automatic switching








SF or SD is made.






6




Exerciser




Test switching control system.




0 1 0 0






7




Reverse request




Respond operation of switching




0 0 1 0








to requesting source after








receiving request for forced








switching or signal failure








or wait to restore.






8




No bridge




Inhibit all switchings by any




0 0 0 0







required




of the following switching








requests, with the working








state held.























TABLE 4









z3 BYTE







b7, b8




DESCRIPTION











0 0




Normal state






1 1




PG-AIS*






1 0




PG-FERF











*PG-AIS = path group AIS.













3. Surveillance and Control System




This section describes a surveillance and control system for the network system related to the embodiment.





FIG. 14

is a block diagram for a configuration of the network system related to the embodiment.




Each of the LT-MUXes and the 1R/3R-REPs


2


,


3


has a surveillance and control function


1001


and an OpS-IF


1002


for connection with an OpS (operation system)


1000


. The surveillance and control are made under control of the OpS


1000


which governs the surveillance and control of the system.




The embodiment makes a wavelength multiplex of a surveillance and control signal with a main signal on the STM-64 interface before transmitting the multiplexed signal to monitor and control the 1R/3R-REPs


2


,


3


having no OpS IF


1002


remotely. That is, the OpS


1000


gives a direction signal to the equipment having the OpS IF


1002


to make the equipment superimpose the direction signal onto the surveillance and control signal, or makes the 1R/3R-REP having no OpS IF


1002


transfer an alarm detected or generated by the 1R/3R-REP to the equipment having the OpS IF


1002


. Alternatively, it can be made that the 1R/3R-REP should have the OpS IF


1002


to allow the OpS


1000


to monitor and control the 1R/3R-REP directly.




In turn, the surveillance and control signal of 384 kb/sec is transferred by a light of the same 1.48 μm wavelength as that of a pumping light source of the 1R-REP


2


. The surveillance and control signal, as shown in

FIG. 22

, also has a 48 byte frame length for a 1 msec frame period, 24 bytes (192 kb/sec) of which are allocated to a DCC (data communication channel) for the remote control, 8 bytes (64 kb/sec) for an order wire, and 6 bytes (48 kb/sec) for the alarm transfer. The surveillance and control signal allows each of the 1R/3R-REPs


2


,


3


to inform the state and alarm. That is, each of the 1R/3R-REPs can generate its own monitoring information and repeat the surveillance and control signal generated by the preceding 1R/3R-REP as well. The state monitoring is made at intervals of 1 sec so that an access collision cannot happen even if the number of the 1R/3R-REPs is around 100.




Also the surveillance and control signal has 1 byte allocated there to the 1R-REP section that has a feature equivalent to that of the usual AIS. The 1R/3R-REP having detected a fatal failure, such as loss of the main signal, transfers its own ID to the succeeding repeater using the one byte. This 1R/3R-REP


2


,


3


repeats the one byte to the LT-MUX


1


. This allows informing of the 1R/3R-REP section AIS at intervals of 1 msec. If it is used, the 3R-REP converts it to an S-AIS (section alarm indication signal).




The features of the surveillance and control system are charted in Tables 5 and 6. Surveillance and control items are charted in Table 7.














TABLE 5









ITEM




DESCRIPTION




NOTE


























Surveillance




(1)




LT-MUX




1R/3R-






and control





Has OpS-IF and is started by direction




REP can






equipment





by OpS.




have







(2)




1R-REP




OpS-IF.








Has RMT-IFs, such as DCC-IF and








ALARM-IF, and is started by direction








by surveillance and control signal.







(3)




3R-REP








Same as 1R-REP.






Surveillance




(1)




Physical characteristics




Frame






and control





Frame length: 48 bytes.




synchro-






signal





Frame period: 1 msec.




nization








Rate: 384 kb/sec.




by CMI








Wavelength: 1.48 μm.




code rule








Line code: CMI.




violation.







(2)




Generation method




To








Generation by LT-MUX and




increase








1R/3R-REP.




reliability.







(3)




Transfer method








Is wavelength-multiplexed with the








main signal before being transferred.








1R/3R-REP determines either repeat or








reception with destination ID added on








surveillance and control signal.








For repeat, 1R/3R-REP stores it in








the reception buffer before transmis-








sion.







(4)




Access to 1R/3R-REP








Access can be made from either west or








east.






Monitoring




(1)




Amount of information:






method





4 bytes of surveillance and control








signal.







(2)




Monitoring interval/alarm transfer




Equivalent








interval: 1 sec.




to feature








However, if fatal failure, such as




of SONET








loss of signal, is detected,




F1 byte.








1R/3R-REP section AIS is transferred








at intervals of 1 msec.







(3)




Transference can be made to either








west and east.


























TABLE 6











ITEM




DESCRIPTION




NOTE





























Control




(1)




Surveillance and control signal




Setting can







method





has DCC area of 24 bytes




be made also









(equivalent to 192 kb/sec)




from OpS if









provided therein for setting




necessary.









surveillance and control items.








(2)




Surveillance and control signal









has order wire area of 8 bytes









(equivalent to 64 kb/sec)









provided therein. This allows









maintenance communication.








(3)




Access can be made from either









west or east.








(4)




Response is made after









execution of instruction.























TABLE 7





























































As shown in

FIG. 7

, if any of the monitoring items is at failure, the equipment transfers the alarm. The alarm detection and transfer are made for the four layers, including the 1R section layer, the 3R section layer, the LT section layer, and the path layer.




The 1R section layer deals with any of the alarms detected by the 1R-REP


2


. The alarm is transferred by the surveillance and control signal. The 1R section layer processes the following items.




(a) Optical fiber disconnection: The main signal input and the surveillance and control signal input are disconnected by an optical fiber disconnection.




(b) Loss of main signal: The main signal input is lost by a preceding 1R/3R-REP stage failure.




(c) Loss of surveillance and control signal: The main signal input is lost by a preceding 1R/3R-REP stage failure.




(d) Surveillance and control signal LOF (loss of frame): The frame synchronization surveillance and control signal is lost.




(e) Surveillance and control signal FCS (frame check sequence) error: A code error is detected by checking the FCS of the surveillance and control signal.




(f) 1R section failure REP identification: The 1R-REP having detected a fatal failure writes its own ID into a predetermined byte provided in the surveillance and control signal before generating the surveillance and control signal. This accomplishes the feature of F1 byte for the SDH recommended by the CCITT.




The 3R section layer performs processes about an RSOH (regenerator section overhead) of the STM frame.




(a) Main signal LOF: Loss of frame of the main signal is detected with A1 and A2 bytes.




(b) Error rate degradation: MER and ERR MON are generated with use of B1 byte,




(c) F1 byte process: If it detects a fatal failure, the 3R-REP writes its own ID into the F1 byte of the sending STM frame. Also, if it receives the surveillance and control signal indicating that the preceding the 3R-REP is at failure, the 3RREP writes the ID in a predetermined byte into the F1 byte of the sending STM frame.




(d) S-AIS detection, generation, and transfer: S-AIS process is made.




The LT section layer performs processes about an MSOH (multiplex section overhead) of the STM frame.




The path layer performs processes about a VC-3/4 POH (path overhead) of the STM frame.




In turn, the alarm of the 1R section is sent to the LT-MUX through 1R-REP and 3R-REP by the surveillance and control signal.




For any of the fatal failures, such as loss of the main signal, if the alarm is transferred through the 3R-REP, then the 3R-REP converts it to S-AIS.

FIG. 15

is a sequence diagram for transfer of the alarm in the network system.




4. Optical Transmission System




This section describes an optical transmission method for the optical transmission system related to the embodiment.





FIG. 16

is a block diagram for the optical transmission system for the long distance system.




As shown in the figure, the embodiment includes a modulator integrated light source module


200


of 1552 nm wavelength having little chirping as a sending light source for the LT-MUX


1


and the 3R-REP


3


. To suppress an SBS (stimulated Brilloiun scattering) caused in the optical fiber, the embodiment uses the spectrum broading so that a signal of a low-frequency oscillator


201


is applied to a laser section of the modulator integrated light source module


200


to make a light frequency modulation. Optical booster amplifiers


14


and


34


use a bidirection pumping method for which a pumping light source of 1480 nm wavelength is used. The transmission power and chirping quantities of a modulator are optimized to accomplish the longest regeneration distance of 320 km.




To transmit the supervisory signal, a supervision light source


202


of 1480 nm wavelength range provided in the optical booster amplifier is used. The supervisory signal is wavelength multiplexed with the main signal before being transmitted to a downstream. To prevent output of the light booster from decreasing, a WDM (wave division multiplex) coupler


203


for wavelength multiplex of the surveillance and control signal with the main signal is made to also serve as WDM coupler for laser pumping.




A forward pumping optical pre-amplifier


15


,


35


having a pumping source of 1480 nm range accomplishes highly sensitive reception.




On the other hand, to receive the supervisory signal, a WDM coupler


210


for pumping Erbium-doped fiber is used to detect the supervisory signal, which is received by an exclusive receiver. This minimizes degradation of the NF (noise figure). With the use of the light booster amplifiers


14


,


34


and light pre-amplifiers


5


,


35


, the distance between the LT-MUX


1


and the 3R-REP


3


can be made 120 km if they are directly connected together.




The 1R-REP


2


has two Erbium-doped fibers


211


and


216


and pumping light sources of 1480 nm wavelength range used therein. The former laser pumping stage


212


pumps forward, and the latter three laser pumping stages


213


,


214


, and


215


pump bidirectionally. This accomplishes both lower NF and higher output power. For reception of the supervisory signal by the 1R-REP


2


, a WDM coupler


217


for pumping the first Erbium-doped fiber


211


stage is used to detect the supervisory signal for an exclusive receiver


218


. This minimizes degradation of the NF below 0.2 dB to accomplish an optimum reception of the supervisory signal.




For transmission of the supervisory signal by the 1R-REP


2


, a light source


219


of 1480 nm wavelength range for the supervisory signal is used to wavelength-multiplex with the main signal before being transmitted to a downstream. wavelength multiplexing of the supervisory signal with the main signal is made by using a WDM coupler


220


which also serves to pump the latter Erbium-doped fiber


216


.




To prevent output of the light booster from decreasing, the WDM (wave division multiplex) coupler


203


for wavelength multiplex of the surveillance and control signal with the main signal is made to also serve as the WDM coupler for laser pumping. In such a way as described above, with the surveillance and control signal demultiplexed and multiplexed at the input and the output of the 1R-REP


2


respectively, an inter-office cable connected to the equipment can be used to inform a failure to the downstream even if the failure is the input signal disconnection or in the transmission medium within the 1R-REP


2


.





FIG. 17

is a block diagram for the optical transmission system for a short distance system.




The short distance system, as shown in the figure, like the long distance system, uses a modulator integrated light source module


200


of 1552 nm wavelength for a transmitting light source. The short distance system is different from the long distance system in that a transmitter of the short distance system uses a semiconductor light amplifier


230


as an optical booster to make the transmitter small, and a receiver uses an optical receiver


231


of small size and low power consumption having a superlattice APD of low noise and wide frequency response.




If it has a high optical power input thereto, the optical fiber has an SBS caused, resulting in degradation of the transmission characteristics. For the CW light, the SBS is caused with the optical fiber input power higher than +6 dBm. In modulation, the SBS is caused by blight-line spectra contained in the signal light. It is generated at a light power level higher than the one for the CW light.




To suppress the SBS, the embodiment uses a way that the generated laser light is modulated with a low frequency signal to broaden the light spectra equivalently. The suppression of the SBS by broadening the light spectra is described in an article entitled “Suppression of Stimulated Brilloiun scattering and Brilloiun Crosstalk by Frequency Sweeping Spread-Spectrum Scheme,” Journal Optical Communications, Vol. 12, No. 3, pp. 82-85 (1991), A. Hirose, Y. Takushima, and T. Okoshi.





FIG. 18

is a block diagram for a clock transit system for the optical transmission system.




A clock for process of section overhead of transit signals in the LT-MUX


1


and 3R-REP


3


, as shown in the figure, is an extracted clock smoothed by a PLL. The PLL has a time constant which is set in an order of msec that can almost completely suppress random jitters superimposed through the transmission circuit and line. A low-speed wander of the transmission clock is transferred by a pointer justification feature of the section overhead. With these, the 3R-REP


3


can make the repeat without accumulation of the jitters, it is free of the jitter accumulation due to continuation of an identical code.




In transmission of the SDH section overhead, all the section overhead bytes except parts of the first line are scrambled. (

FIG. 19

shows the parts of the first line, including 4 bytes containing the last 2 A1 bytes and first 2 A2 bytes, 64 C1 bytes, and succeeding 2×64 fixed bytes.) This prevents repetition of a fixed pattern as much as hundreds of bytes, reduces a pattern jitter, and averages output of a timing filter. If a 4-byte synchronous pattern is used, a frame synchronization protection is longer than 10 years in average misframe interval for five consecutive forward protection, and is lower than 1% in misframe probability and rehunting probability for two consecutive backward protection.




5. Description of 1R-REP




This section describes the 1R-REP


2


.





FIG. 20

is a block diagram for the 1R-REP. Table 8 charts major features of the 1R-REP


2


.













TABLE 8









ITEM




DESCRIPTION

























Main signal




Signal wavelength




1.552 μm ± 0.001 μm






interface




Mean light output




+10 to +12 dBm







Input light level




−18 to 0 dBm







Noise figure




Lower than 7 dB







Pumping method




Bidirectional pumping of








Erbium-doped fiber, with








1.48 μm pumping lasers.












Surveillance and control




• Transference of surveillance






method




and control signal by 1.48 μm







wavelength multiplex.







• Implementation of







surveillance and control







section in main signal unit.






Physical implementation




300 mm high × 3 shelves per bay






method




(1800 × 795 × 600 mm)






Cooling method




Natural convection, with







convection guiding plate of







100 mm high.






Accommodation of systems




Two systems per shelf (one







system contains both east and







west systems)






Environmental conditions




Temperature: 10 to 40° C.







Humidity: 20 to 80%






Input power condition




−42 to −53 V














As shown in

FIG. 20

, the 1R-REP optical transmission system consists of two amplifier stages, including an optical pre-amplifier


301


for magnification with a low noise and an optical booster amplifier


320


for high power magnification. An output of the optical pre-amplifier


301


is connected to an input of the optical booster amplifier


320


. This accomplishes a low noise, high power output characteristic in a wide dynamic range.




Description of the pre-amplifiers is ignored here as it was already made previously by reference to FIG.


16


.




The 1R-REP


2


can monitor light outputs and intermediate signal powers and detect opening of the outputs it can control and monitor a gain of each optical amplifier stage. As described previously, the 1R-REP


2


also can receive and transmit the surveillance and control signal of 1.48 μm wavelength. The monitor and control and processing of the surveillance and control signal are made by an surveillance a supervisory signal processor/automatic power control circuit


310


.





FIG. 21

is a block diagram for a package construction of the 1R-REP


2


. The main signal system of the 1R-REP


2


, as shown in the figure, comprises two packages, including a pre-amplifier package having the low-noise optical pre-amplifier


301


and a booster amplifier package having the high-power optical booster amplifier


320


. As will be described later, a single bay having a plurality of shelves, each of which has two systems and the OpS IF as a common section.




The ground 1R-REP


2


, like the LT-MUX


1


and the 3R-REP


3


, has features of preventive maintenance, failure identification, and workability increase.




These features facilitate troubleshooting for each 1R repeater section. As for the 1R repeater section overhead providing a feature of a surveillance and control communication channel between offices having the 1R-REP


2


, as described previously, it uses the surveillance and control light of 1.48 μm wavelength.




The following describes monitor of the 1R repeater section and process of the 1.48 μm surveillance and control signal in detail. It should be noted that the surveillance and control made by the 1R-REP


2


are similarly made by the LT-MUX


1


and the forward pumping optical pre-amplifier


35


and the optical booster amplifier


34


of the 3R-REP


3


.




Table 9 lists surveillance and control items of the 1R-REP


2


.

















TABLE 9













Surveil-




Alarm




Signal




Optical fiber disconnection







lance





failure




Main signal (Preceding REP










failure)










Loss of surveillance and










control signal (Preceding REP










failure)










Surveillance and control










signal LOF (CMI)










Surveillance and control










signal FCS (frame check










sequence) error









Equipment




Output open









failure




Main signal transmit failure










Surveillance and control










signal transmit failure










Optical amplifier equipment










failure










Surveillance and control










equipment failure










Power source system failure
















Monitor




Input signal level









Intermediate signal level









Output signal level









Pumping LD temperature









Pumping LD bias









Surveillance and control LD temperature









Surveillance and control LD bias









Gain














Control




Year and date setting and reading








Output halt and release








Failure section determination















As shown in

FIG. 9

, the 1R-REP


2


provides the following processes with use of surveillance lights and control signals marked with an encircled number in FIG.


20


.




Number {circle around (1)} in

FIG. 20

denotes a surveillance light signal which is taken by a PF-WDM out of the input light having been composed of the main signal light of 1552 nm wavelength and the surveillance and control light signal of 1480 nm wavelength. The surveillance light signal is 3R-processed and converted to an electrical signal by a supervisory signal receiver. The surveillance light signal is used by the automatic power control circuit surveillance signal processor


310


to detect the supervisory signal input disconnection.




Number {circle around (2)} in

FIG. 20

denotes a monitor light branched from a light output of the low-noise amplifier section by a CPL. The monitor light is used by the automatic power control circuit surveillance signal processor


310


to control the gain, to monitor the input state, and to monitor the intermediate power.




Number {circle around (3)} in

FIG. 20

denotes another monitor light branched from a light output of the high-power output amplifier section by another CPL. This monitor light is taken out through a BPF. The monitor light is used by the automatic power control circuit surveillance signal processor


310


to control the gain and to monitor the output state.




Number {circle around (4)} in

FIG. 20

denotes still another monitor light branched through the CPL from a light reflected from the output end. This monitor light is used by the automatic power control circuit surveillance signal processor


310


to detect opening of the output.




Number {circle around (5)} in

FIG. 20

denotes control signals used by the automatic power control circuit surveillance signal processor


310


for stabilization-control of the output of the pumping source and to monitor LD states.




Number {circle around (6)} in

FIG. 20

denotes the surveillance and control signal sent from the automatic power control circuit surveillance signal processor


310


. The surveillance and control signal is converted to an optical signal by the surveillance and control light source of 1480 μm wavelength. The optical signal is composed with the light output of the high-power output amplifier by the BB-WDM. The surveillance and control signal is used to monitor the surveillance light source LD state and to detect the supervisory signal transmit failure.




It is needed for the 1R-REP


2


that depending on the surveillance results and the like of the surveillance items, as described above, identification should be made for the transmission line alarms as to loss of the main signal, transmit failure of the main signal, loss of the supervisory signal, the input fiber disconnection, and the like. Such failure points can be identified by a judgement logic comprehended of the surveillance items {circle around (1)}, {circle around (2)}, and {circle around (3)}. Also, the 1R-REP


2


can detect the equipment failures of the optical amplifier repeater section for preventive maintenance of equipment. Further, the 1R-REP


2


has external control features of output shutdown for safe work.




Furthermore, the 1R-REP


2


, as described above, can not only send the surveillance and control information to the downstream equipment depending on the surveillance results of the surveillance and control items, but can also repeat to transfer to the downstream equipment the surveillance and control information received from the upstream equipment.




Still furthermore, the embodiment does not only inform any of the failures of the 1R-REP


2


to the downstream, but also facilitates judgement of a failure point in each of the 1R repeater sections and also maintains on the inter-office fiber the surveillance and control communication channel between the office having the 1R-REP


2


. To do these, the surveillance and control signal light is terminated once for each 1R-REP


2


before being repeated to the downstream through automatic power control circuit surveillance signal processor


310


to transfer. This has the advantage that the surveillance information can be transfered by a single wavelength even if the number of repeaters is increased.




In turn, if the wavelength used for the supervisory signal is out of the range of the optical amplifier, this will not cause saturation in the optical amplifier, and thus will not affect the main signal. For this reason, the light of 1.48 μm is used as described above. This light provides minimal transmission line fiber loss of the main signal waveform, and allows using a WDM (wave division multiplex) coupler to compose and divide the pumping light in common.




The CMI code is used to send the surveillance and control signal with the CMI code used, a dc component and zero continuation can be suppressed. Also, a frame synchronizing circuit can be made up of relatively few components by a frame synchronization method of code violation.





FIG. 22

is a format for the surveillance and control signal for use in the surveillance and control of the 1R-REP


2


.




The embodiment accomplishes the feature of remote control in a way as that shown in FIG.


22


. The surveillance and control signal used is of a 48 byte-long frame for period of 1 msec at a rate of 384 kb/sec, and the DCC of 192 kb/sec is maintained within the surveillance and control signal. The frame has 1 byte for information of severe failures every period of 1 msec. This accomplishes the feature equivalent to the F1 byte of the SDH.




6. Description of LT-MUX




This section describes the LT-MUX


1


in detail.





FIGS. 23 and 24

are block diagrams for hardware constructions of the long distance system related to the embodiment. Table 10 charts major features of the LT-MUX


1


. As for differences of the hardware construction of the LT-MUX


1


for use in the short distance system from those of the long distance system, they will be described below as necessary.













TABLE 10












DESCRIPTION














FOR LONG-




FOR SHORT-







DISTANCE




DISTANCE






ITEM




SYSTEM




SYSTEM
















Intra-




Transmission rate




155.52 Mb/sec (STM-1) × 64 series or






office





622.08 Mb/sec (STM-A) × 16 series.






interface




Transmission




Scrambled binary NRZ.







line code







Error rate




Lower than 10


−11









Light source




1.31 μm +0.05 μm to −0.04 μm (STM-1);







wavelength




1.31 μm +0.05 μm to −0.05 μm (STM-4)







Average light




−17 to −11 dBm (STM-1): −15 to







output




−8 dBm (STM-4)







Maximum




Higher than −8 dBm







detectable power







Minimum




Lower than −24 dBm (STM-1);







detectable power




Lower than −23 dBm (STM-4)







Redundancy




1 + 1 dual







configuration






Inter-




Transmission rate




9953.28 Mb/sec (equivalent to STM-64)






office




Transmission




Scrambled binary NRZ (non-return






interface




line code




to zero)







Error rate




Lower than 10


−11









Light source




1.552 ± 0.001 μm, with chirping







wavelength




parameter a being 1.0 ± 0.2















Average light




−10 to +12 dBm




−5.6 to +6.6 dBm







output




Direct LT








connection:








°15 to °16 dBm







Maximum




Higher than −7




Higher than







detectable





−10 dBm







power







Minimum




Lower than −27




Lower than







detectable




dBm




−23 dBm







power














Redundancy




Mesh switching using virtual ring at







configuration




VC-¾ level












Surveillance and




Surveillance control by OpS interface.






control method




1R-REP surveillance and control by







1.48 μm wavelength multiplex.






Physical implementation




300 mm high with 4 shelves






method




(1800 × 795 × 600 mm)






Cooling method




Push-pull type forced air cooling, with







large fan.






Accommodation of systems




Two systems per rack.






Environmental conditions




Temperature: 10 to 40° C.







Humidity: 20 to 80%






Input power condition




−42 to −53 V















FIG. 23

is for the inter-office transmission line of the LT-MUX


1


.

FIG. 24

is for the intra-office transmission line of the LT-MUX


1


. The LT-MUX


1


, as shown in the figures, comprises a high-speed IF shelf


600


, a low-speed IF shelf


700


, a supervisory control/OpS


650


, an OH IF


660


, and a clock section


670


.




The high-speed IF shelf


600


comprises an OPTAMP S


601


having features as the optical booster amplifier


14


of the transmitting system, an OPTAMP R


603


having features as the optical pre-amplifier


15


of the receiving system, a 10G IF S


602


, a 10G IF R


604


, and a plurality of SOH


605


boards. The lowspeed IF shelf


700


comprises a plurality of SELs


701


, and a plurality of intra-office IF


702


packages. The high-speed IF shelf


600


and the low-speed IF shelf


700


are connected together by an intra-equipment interface of 155 Mb/sec rate.




The embodiment has a high-speed interface


600


-


1


, an SEL


701


-


1


, and an intra-office interface


702


-


1


to have a redundancy feature of 1+1 section switching type. These blocks are not needed if the section switching is not made.




Tables 11 and 12 chart the features of the LT-MUX


1


.















TABLE 11










BLOCK








ITEM




NAME




FEATURE




NOTE



























1




10G IF-S




(1)




Optical booster amplification








OPTAMP-S




(2)




1R repeater surveillance









and control signal light









transmission








(3)




STM-64 signal E/O conversion








(4)




10 GHz PLL








(5)




STM-64 RSOH transmission








(6)




Physical rate conversion of









155 Mb/sec to 10 Gb/sec






2




10G IF-R




(1)




Optical preamplification







OPTAMP-R




(2)




1R repeater surveillance and









control signal light reception








(3)




STM-64 signal D/E conversion









and clock extraction








(4)




STM-64 RSOH termination








(5)




Physical rate conversion of









10 Mb/sec to 155 Gb/sec






3




SOH




(1)




STM-64 MSOH process








(2)




Pointer conversion of AU-3,









AU-4, and AU-4-4c








(3)




POH monitor of VC-3, VC-4, and









VC-4-4c and line test






4




SEL




(1)




System 0/system 1 selection of









STM-1/STM-4 intra-office









transmission line








(2)




System 0/system 1 phase matching









of VC-3, VC-4, and VC-4-4c









(hitless switching)








(3)




APS protocol control for









intra-office transmission line









switching






5




Intra-IF





STM-1 or STM-4 intra-office









transmission line termination








(1)




E/O and O/E conversions








(2)




SOM process








(3)




Pointer conversion of AU-3,









AU-4, and Au-4-4c








(4)




POH monitor of VC-3, VC-4, and









VC-4-4c and line test









Number of accommodated lines is









STM-1 × 8 or STM-4 × 2 per









board.






6




SVCONT




(1)




Information collection in







(LIF)





low-speed IF shelf, operation









of performance surveillance









information, and event









made of alarm data









• Intra-office section









• AU pathbus









• Surveillance in equipment








(2)




Alarm priority processing and









failure determination








(3)




Distribution and status reading of









control information in shelf









• Software strap of intra-office









section









• AU line test









• Selected status of redundancy









system

























TABLE 12










BLOCK








ITEM




NAME




FEATURE




NOTE



























7




SVCONT




(1)




10G high-speed transmission IF,








(HIF)





surveillance information collection









of submarine repeater, operation of









performance surveillance









information, and event made









of alarm data









• 1R repeater section









• Multiplex section









• AU path









• Surveillance in equipment








(2)




Alarm priority processing and failure









determination








(3)




Distribution and status reading









of 10G high-speed transmission









line IF and repeater control









information









• Software strap









• AU line continuity check









• Control and status reading of









repeater






8




SEMF




(1)




OpS message conversion








(2)




Time management and history









processing








(3)




Emergency start-up of backup









memory








(4)




Switching control of clock section









and SVCONT








(5)




Processing of common system alarm






9




OpS IF




(1)




OpS message communication









processing






10




RMT IF




(1)




Remote surveillance and control









communication by DCC of multiplex









section overhead (MSOH)






11




CREC




(1)




B/U conversion of 64 kHz + 8 kHz









clock






12




CDIS




(1)




Clock generation (PLL) and









distribution in equipment






13




CSEMD




(1)




Transmission of extracted clock






14




OH IF




(1)




Input/output of overhead signal









outside equipment








(2)




OAM processing by overhead signal















FIG. 25

is a relationship of multiplex and demultiplex between the STM-64 frame and the STM-1×64 supported by the LT-MUX.




A 10G E/O


610


of a 10G IF S


602


and an OPTAMP S


601


form the transmitter of the LT-MUX


1


, and a 10G O/E


611


of a 10G IF R


604


and an OPTAMP R


603


form the receiver of the LT-MUX


1


.




The following describes the transmitter and the receiver mentioned above.





FIG. 26

is a block diagram for the transmitter of the LT-MUX


1


forming the long distance system.




The transmitter, as described previously, comprises the 10G E/O S


610


having the high-speed multiplex circuit


682


for converting d 622 Mb/sec, 16-parallel signal to 9.95 Gb/sec signal in a way of a 16-bit multiplex (STM-


64


) and the electro-optic converter


681


and the OPTAMP S


601


which is an optical amplifier.




As shown in the figure, the embodiment uses an external modulation of electric field absorption type for electro-optic conversion. The OPTAMP S


601


is formed of an optical fiber amplifier. The optical fiber amplifier is separately implemented in its respective package in view of its occupying area and consumption power. The transmitter further has a temperature control circuit


683


and an optical output control circuit


684


the long-distance transmission can be made even if environmental conditions around the electro-optic converter


681


and the OPTAMP S


601


change. Description of the transmission operation is ignored as it was already made by reference to FIG.


16


.





FIG. 27

is a block diagram for the transmitter of the LT-MUX


1


forming the short distance system.




The transmitter of the LT-MUX


1


forming the short distance system, as described in the figure, has no OPTAMP S


601


. The 10G IF S


602


, unlike that of the long distance system, uses a semiconductor optical amplifier of preferably smaller size and lower power consumption for optical amplification in the 80-km transmission. The semiconductor optical amplifier can be made to occupy as narrow an area as the modulator with LD, and can be implemented in the 10G IF S


602


shelf. The embodiment, as shown in the figure, uses a modulator of an electric field absorption type for the external modulator. The electric field absorption type modulator is integrated to a module of small size as electric field absorption type devices are structurally practical to integrate with the laser diode for the light source.





FIG. 28

is a block diagram for the receiver of the LT-MUX


1


forming the long distance system.




The receiver comprises the OPTAMP R


603


which is an optical amplifier and the 10G O/E


611


having an opto-electric converter


693


and a high-speed demultiplex circuit


692


. The OPTAMP R


630


, as shown in the figure, is made up of an optical fiber amplifier having an optical pre-amplifier feature, and is separately implemented in its respective board. The opto-electric converter


693


is made up of a front module, an amplifier, a timing extractor, and a discriminator circuit. The highspeed demultiplex circuit


692


converts the 9.95 Gb/sec signal to 622 Mb/sec in a way of parallel demultiplex. Description of the reception operation is ignored as it was already made by reference to FIG.


16


.





FIG. 29

is a block diagram for the receiver of the LT-MUX


1


forming the short distance system.




The short distance system is different from the Iona distance system in that the short distance system has no OPTAMP R


603


and uses an APD


694


for opto-electric conversion. As the APD


694


is capable of more sensitive reception than Pln-PD, the short distance system needs no optical amplifier, thus resulting in a smaller system. In turn, if the LT-MUX


1


and the ADM switch are combined to form the small. scale switching node


120


as in

FIG. 6

, the high-speed IF shelf, the low-speed IF shelf


700


, and a 40G switch shelf are combined as shown in FIG.


30


. The 40G switch shelf comprises multiplexing circuits


901


for multiplexing the input signals to feed to time-division switches


903


, the time-division switches


903


, and demultiplexing circuits


902


for demultiplexing the signals from the time-division switches


903


. An interface of the multiplexing circuits


901


and the demultiplexing circuit


902


is the intra-equipment interface.




In turn, the signal from the transmission line is processed by the high-speed IF shelf


600


before being directly input to the switch without the low-speed IF shelf


700


. The signal to be dropped into the office, is connected to the low-speed IF shelf


700


. As for the signal to be passed to the another node, it is connected to the high-speed IF shelf


700


before being fed out to another node. That is, the signal from the transmission line is not converted as to interface by the lowspeed interface before being connected to the switch, as usual.




But, the high-speed IF shelf


600


is directly connected with the switch. This can make the equipment smaller.




If the small scale switching node


120


or the large scale switching node


110


is constructed to have the cross-connection switch feature, the 40G switch in

FIG. 30

is replaced by a multi-stage switch configured of a plurality of 40G switch shelves.




As described above, the embodiment can appropriately combine the high-speed IF shelves


600


, the low-speed IF shelves


700


, and the 40G switch shelves


900


in the building block way. This allows accomplishment of a desired equipment with use of the common shelves in a minimized construction. Also, the embodiment allows accomplishment of the 3R-REP


3


by combination of the boards of the high-speed IF shelf


600


as will be described later.




The following describes the surveillance and control system for the LT-MUX


1


.





FIG. 31

is a block diagram for extracted parts serving as the surveillance and control system for the LT-MUX


1


.





FIG. 32

lists features of the functional blocks.




Tables 13, 14, 15, and 16 chart features of the surveillance and control system.




In

FIGS. 31 and 32

, the SVCONT


703


is installed for each low-speed IF shelf. The SEMF


651


, the OpS IF


652


, and RuT IF


653


are equipped in the common a shelf as will be described later.
















TABLE 13











FEATURE




DESCRIPTION




NOTE




























1




Path




(1)




Switch control memory is




Control







setting





updated to set path according




system









to the control message from the









operation system outside









equipment.








(2)




Path setting units include:









a. Units of VC-3









b. Units of VC-4









c. Units of VC-4c (600M at max)








(3)




This feature is an option for









implementation of crossconnection









feature






2




Software




(1)




Control register of each section




Control







strap





in equipment is updated to set




system







setting





operation mode (software strap)




NOTE 1:









according to control message from




Upon use









operation system outside




of









equipment.








(2)




Major software strap features




section









include:




protection









a. Transference approval or




feature









inhibition of transmission line









system alarm









b. Threshold of error rate









degradation









c. Protection time of switching









control (NOTE 1)






3




Path




(1)




Test access point is set to confirm




Control







test





continuity and set quality in units




system









of path according to the control









message from the operation system









outside equipment.








(2)




Path testing units include:









a. Units of VC-3









b. Units of VC-4








(3)




Test pattern conforms to CCITT









Recommendation 0.151






4




Redundancy




(1)




The operation system switches




Control







system





over functional components of




system







switching





equipment having redundancy form




Surveil-







in





according to the control




lance







equipment





message from the




system









operation system outside









equipment. (Forced









switching)








(2)




As results of equipment diagnosis,









the operation system switches over









to the protection side from function









component of equipment judged at









failure. (Autonomous switching)








(3)




Operation modes of redundancy









system include:









a. Automatic mode, allowing auto-









nomous switching









b. Forced selection mode









c. Lock-out mode


























TABLE 14











FEA-









TURE




DESCRIPTION




NOTE




























5




Con-




(1)




Implementation states of functional




Surveil-







figu-





components of equipment are monitored,




lance







ration





and the database for configuration




system







man-





management in the control system is







age-





automatically updated as needed.







ment




(2)




When the implemented functional









component does not logically match









with the physical implementation









position, then an alarm is issued.








(3)




Management units for functional









components of equipment include:









a. Board









b. Board group









c. Shelf






6




Alarm




(1)




Transmission line system alarms are




Surveil-







trans-





collected from line termination




lance







ference





feature blocks and path connection




system









feature blocks to detect generation









and restoration of alarms before









transmission line system alarms are









made into an event.








(2)




On basis of diagnosis results of









equipment failure, equipment alarms









are made into an event.








(3)




Contents of these alarms made into









a event are converted to messages









before being informed to external









surveying operation system.






7




Perfor-




(1)




Performance information, such as




Surveil-







mance





a bit error, are collected from line




lance







man-





termination feature blocks and path




system







age





conncection feature blocks to







ment





calculate and generate performance









management information for transmis-









sion lines and paths.








(2)




The performance management informa-









tion includes:









a. CV (code violation)









b. ES (errored second)









c. SES (severely errored second)








(3)




Types of registers for history









management includes:









a. 1-sec register









b. 15-min register









c. 1-day register


























TABLE 15











FEA-









TURE




DESCRIPTION




NOTE




























7




Equipment




(1)




Failure surveillance information is




Surveil-







diagnosis





collected from functional components




lance









of equipment, and a specific




system









functional component having a









hardware failure generated is









identified on the basis of the









failure judgement map provided in









the surveillance and control system.








(2)




Specific functional component having









a hardware failure generated is









logically disconnected, and the









operation system switches over









from the functional component of









redundancy configuration to the









protection side.








(3)




Equipment information is sent out to









inform existence of a functional









component having a failure generated.






9




Section




(1)




If a section failure happens, section




Control







switching





switching is controlled on the basis




system







control





of MSP protocol.




Surveil-








(2)




Switching system includes the




lance









following manners:




system









a. 1 + 1 (without switch-back)




MPS:









b. Bi-directional switching




Multiplan








(3)




Switching is caused by include:




Section









a. SF switching (LOS, LOF, S-AIS,




Protection









and hardware failure)









b. SD switching (MER)









c. Forced switching (OpS command)








(4)




This feature is optional.






10




Path




(1)




If a path failure is detected with




Control







switching





generation of a failure in the ring




system







control





meshed network, section switching is




Surveil-









controlled on the basis of MSP




lance









protocol.




system








(2)




Switching system includes the




PGP =









following manners:




Path









a. 1 + 1 (with switch-back)




Group









b. Bilateral switching




Protection








(3)




Switching is caused by include:









a. SF switching (LOP, P-AIS, and









hardware failure)









b. SD switching (MER)









c. Forced switching (OpS command)








(4)




This feature is optional for









implementation of cross-connection









feature.


























TABLE 16











FEA-









TURE




DESCRIPTION




NOTE




























11




History




(1)




Variety of events generated as to




Control







manage-





transmission line received signals




system







ment





and equipment statuses are recorded




Surveil-









and managed as history information.




lance








(2)




History information to be managed




system









includes:









a. Redundancy system switching









history









b. Signal performance history









c. APS information changing history






12




Backup




(1)




If the operation state in equipment




Control







infor-





is changed, then the changed state is




system







mation





automatically recorded in nonvolatile




NOTE 1:







manage-





memory as the latest information.




With use







ment




(2)




Information to be recorded includes:




of cross-









a. Operation information of




connection









redundancy system




feature









b. Information of software strap









c. Path setting information (NOTE 1)








(3)




The following processes are









made with the control message









from the control operation system









a. Update of backup information









b. Comparison with statuses in









equipment









c. Initialization of backup









information






13




Emer-




(1)




If it is powered on, equipment is




Control







gency





autonomously started up for operation




system







start-up





on basis of backup information.






14




Communi-




(1)




Control is made on




Control







cation





communication with the operation




system







control





system outside equipment.




Surveil-








(2)




Communication is of a message form




lance









and has a protocol system on basis of




system









the Q interface of CCITT









Recommendations.








(3)




Two independent communication









links are provided, including









the control system and









surveillance system.






15




OpS




(1)




Control information of message




Control







message





received from operation system is




system







conversion





converted to the command form




Surveil-









specific to equipment.




lance








(2)




Control information and surveillance




system









information of the command form









specific to equipment are converted









to information of message form









before being sent to the









operation system.















FIG. 33

is a block diagram for the redundancy configuration of the transmitting system in the LT-MUX


1


.

FIG. 34

is a block diagram for the redundancy configuration of the receiving system in the LT-MUX


1


.




In general, operations including AU pointer conversion are nonhitlessly switched. To make this hitless, a hitless switching process is needed. In the embodiment, in view of the balance of the features provided in the whole equipment, the AU pointer conversion process is provided in the intra-office interface and the high-speed interface unit. In the SEL


701


between these is provided a hitless switching process feature section which will be described later. As shown in the figures, simplex sections are optical booster amplifier


601


, 10G IF-S


602


and the SOH


605


in the operation form without the 1+1 section switching in the 10 Gb/sec transmission line.




As the intra-office interface is an interface to be connected with an existing intra-office equipment, the redundance configuration follows the manner of the existing equipment. That is, the redundance configuration is made of the 1+1 section switching type of system 0/system 1 without switch-back. The board for the intra-office interface accommodates a plurality of highways. Auto-switching at failure is made in units of transmission line. The intra-office interface board, therefore, has working highways and waiting highways mixed therein. For this reason, for interface package maintenance, a hitless forced switching is needed which will be described later.




The SEL


701


, as shown in

FIGS. 23 and 24

, is arranged it can be added or removed depending on the situation of transmission line accommodation. The SEL


701


, therefore, is arranged so chat it can be automatically switched in units of package in the 1+1 way. Note that if the hitless forced switching which will be described later is made for the SEL


701


, this is hitlessly made by the hitless switching process section.




Now, the following describes the hitless switching process.





FIG. 35

is a block diagram for construction of the hitless switching process feature section for transmission line. Table 17 lists features of functional blocks of the hitless switching process feature section.














TABLE 17









NO.




ITEM




FEATURES

























1




AU pointer




AU pointer byte and AU stuff







termination




operation are read. It is








instantaneously taken in without








protection of consecutive coincidence three








times.






2




2 × 2 SEL




Selector for passing delayed








system through, but storing








preceding system into








VC buffer.






3




VC buffer




FIFO memory for delaying preceding








VC-3, VC-4, and VC-4-4c data.








Adjustable distance difference








is 4 km.






4




VC buffer




Writing address counter







writing




for VC buffer. Only VC-3, VC-4,







control




and VC-4-4c data of input signal are








written according to detection of AU stuff.






5




VC buffer




VC buffer is read in line to AU stuff of the







reading




delayed system. If delay insertion







control




is needed to increase in phase








synchronizing pull-in course,








positive stuff is added.








If it is needed to decrease, negative








stuff is added.






6




Delay




Delay insertion of FIFO is calculated through







insertion




calculation of the writing address minus







calculation




reading address.






7




Phase




Transmission delay difference is detected by







difference




comparison of AU pointer values.







detection






8




Delay




Result of delay insertion calculation is







insertion




compared with result of phase difference







control




detection. If it is necessary to increase delay








insertion, positive stuff is added








on VC buffer reading side. If it








is necessary to decrease








delay insertion, negative stuff is added on the








VC buffer reading side. 2 × 2 SEL is








controlled depending on the








direction of the








delay difference generation.






9




Pointer




New pointer value is calculated by







calculation




comparison of the VC input








phase of the VC buffer








with output frame phase.






10




Pointer




New pointer value is written in VC







insertion




buffer output signal.








Following specific patterns are written in








predetermined positions.
















(1)




On generation of stuff:









Inversion of bits 1 and 0.








(2)




On jump of pointer:









Sending of NDF pattern.








(3)




On AU-4 or AU-4-4c:









CI (concatenation indicator).








(4)




On sending of P-AIS:









All 1 of all bytes.














As depicted in Table 17, the hitless switching process feature section makes the received data, including VC-


3


, VC-


4


, and VC-


4


-c data, of the system having less transmission delay of systems 0 and 1 delay in FIFO memory (VC buffer) as necessary. This makes contents of the output signals of both systems coincide. Detection of the transmission difference is made by comparison of the pointer values. Adjustment of the delay insertion of the FIFO is made with stuff operation of the AU pointer so gradually that the signal of the working system will not be hit: while the phase synchronizing pull-in is made in maintaining the protection system. In writing into the VC buffer, the AU pointer is terminal once before only the VC-


3


, VC-


4


, and VC-


4


-c data are written in the VC buffer. In reading from the VC buffer, on the other hand, reading is made along with the operation of the AU stuff in line with that of the AU stuff in the delayed line. In a phase synchronized state, thus, the system 0 can be made to coincide with the system 1 perfectly not only in the phases of the output VC signals, but also the timings of the AU stuffs. This means that the hitless switching can be made securely even if the frequency of the AU stuff is higher.




The VC buffer is a kind of AU pointer converting circuit. At the time of output, a new AU pointer value is calculated before being inserted into the AU. The calculation principles are the same as those of the usual pointer converting circuit. As the adjustable transmission delay difference is 4 km, the process can be applied not only be applied to the intra-office transmission line, but also to a short or intermediate inter-office transmission line. Thus, in the SEL, the hitless switching process feature section is constructed so that it can be used not only for switching the intra-office interface, but also for switching the 10 Gb/sec transmission line interface.




7. Description of 3R-REP





FIG. 36

is a block diagram for a construction of the 3R-REP


3


. Table 18 lists features of functional blocks of the 3R-REP


3


.













TABLE 18









ITEM




DESCRIPTION

























Main signal




Transmission rate




9953.28 Mb/sec (equivalent to






interface





STM-64)







Transmission line




Scrambled binary NRZ







code




(non-return to zero)







Error rate




Lower than 10


−11


/repeater.







Light source




1.552 μm ± 0.001 μm







wavelength







Average light




+10 to +12 dBm







output







Maximum detectable




Higher than −7 dBm







power







Minimum detectable




Lower than −27 dBm







power












Surveillance and control method




• Surveillance and control







signal transference by







1.48 um wavelength.







multiplexed signal.







• Implementation of







surveillance control section







in main signal unit.






Physical implementation method




300 mm high with 4 shelves per







frame (1800 × 795 × 600 mm).






Cooling method




Push-pull type forced air







cooled type, with large fan.






Accommodation of systems




One system per shelf, with one







bidirectional system of west







and east.






Environmental conditions




Temperature: 10 to 40° C.







Humidity: 20 to 80%.






Input power condition




−42 to −53 V














The 3R-REP


3


makes regeneration through its optical preamplification, O/E conversion, E/O conversion, and optical booster amplification. The 3R-REP


3


also makes the surveillance, alarm transference, and remote maintenance for the 1R repeater section and the 3R repeater section with use of the 1.48 μm surveillance and control light and the RSOH (regenerator section overhead). The boards used in the main signal system are all the same as those of the LT-MUX


1


.




8. Implementation of the 1R-REP, LT-MUX, and 3R-REP




The following describes implementation of the 1R-REP


2


, LT-MUX


1


, and 3R-REP


3


.




First, implementation of the 1R-REP


2


is described below.





FIG. 37

is a front view for an implementation of the 1R-REP


2


.




A rack of the embodiment, as shown in the figure, has three shelves each of which contains two 1R-REP


2


systems, or six 1R-REP


3


systems in total. Each system. comprises two subsystems: the repeaters


301


and


320


. For an unattended office which needs remote monitor and control, these are implemented in the same shelf as the system to which the OpS IF


651


and the like serve. Note that a power source board


810


is for the optical pre-amplifier


301


and the optical booster amplifier


320


.





FIG. 38

shows structures of the optical pre-amplifier


301


and optical booster amplifier


320


forming a single 1R-REP


2


system. The optical pre-amplifier


301


and the optical booster amplifier


320


, as shown in

FIG. 37

, occupy two-fold and four-fold widths in reference to a standard board width respectively, or six-fold width in total. They are naturally air-cooled. Note that a TEC drive circuit in

FIG. 38

is a circuit added to the pumping light source to control a temperature adjustment for thermoelectron cooling devices.




Implementation of the LT-MUX


1


is described below.





FIG. 39

is a frontview for an implementation of the LT-MUX


1


.




The construction shown is for accomplishing the transmission line 1+1 redundancy system switching. The functional boards of the high-speed IF unit


600


and the low-speed IF unit


700


, as shown in the figure, are all doubled as in a working system 0 and a waiting system 1.

FIG. 40

is a front view for an implementation of two systems of the LT-MUX


1


in a single rack without the redundancy configuration.




The 10G IF R


604


package and the 10G IF S


602


board, as shown in the figure, are of two-fold width as these have many components. Similarly, the OPTAMP R


603


board and the OPTAMP S


601


board are of two-fold width.





FIG. 41

is a front view for an implementation of the LT-MUX


1


for constructing the small scale switching node


120


with the 40G switch unit built in as shown in

FIG. 6



b.






In this case, as shown in the figure, are implemented two highspeed interface units


600


, a duplexed 40G switch unit


900


, and a duplexed low-speed IF unit


700


. The 40G switch unit


900


, as shown in

FIG. 42

, is three-dimensionally constructed in view of the flow of its signals. That is, a plurality of boards MUX/DMUX containing a plurality of multiplex/demultiplex circuits


901


and


902


and a time-division switch (TSW)


903


, are three-dimensionally connected together with use of a subpanel for a time switch unit. This construction can be made small.




Implementing the 40G switch into the shelf is made in a way that the TSW


903


is put in front, the 40G switch unit


900


is put into the shelf, and the MUX/DMUX board


901


/


902


is connected with other units on the rear side of the shelf.





FIG. 43



a


is a front view for an implementation of the LT-MUX


1


for constructing the large scale switching node


110


with a multi-stage switch meshed network of a plurality of the 40G switch units built therein.




In this case, as shown in the figure, a plurality of racks have the 40G switch units, the high-speed IF units


600


, and the lowspeed IF units


700


built therein the high-speed IF units


600


, and the low-speed IF units


700


can be connected with the switch multi-stage network.




Finally,

FIG. 44

is a front view for an implementation of the 3R-REP


3


.




As shown in the figure, a single rack has four shelves each of which contains a main signal board, including OPTAMP R


603


, 10G IF R


604


, 10G IF S


602


, and OPTAMP S


601


packages, and a common section, such as an OpS IF


651


. This construction allows a single shelf to complete all the features of a single equipment. It is possible to easily increase or remove the equipment in shelf units as needed.




As described so far, the present invention can flexibly build up the optical transmission system depending on capacities and function required.



Claims
  • 1. An optical transmission equipment which transmits an amplified optical data signal and an optical surveillance signal, comprising:a doped fiber to which an optical data signal is input and which outputs said amplified optical data signal, a surveillance signal source which outputs said optical surveillance signal; and a coupler which multiplexes said amplified optical data signal and said optical surveillance signal; wherein a wavelength of the optical surveillance signal is proximate to the wavelength of the amplified optical data signal, and is able to be demultiplexed from the wavelength of said amplified optical data signal.
  • 2. An optical transmission equipment which transmits an amplified optical data signal and an optical surveillance signal, comprising:a doped fiber to which an optical data signal is input and which outputs said amplified optical data signal; a surveillance signal source which outputs said optical surveillance signal; and a coupler which multiplexes said amplified optical data signal and said optical surveillance signal; wherein a wavelength of the optical surveillance signal is in the range from 1.48 μm to 1.60 μm.
  • 3. An optical transmission equipment according to claim 2, wherein the wavelength of the optical surveillance signal is 1.48 μm.
  • 4. An optical transmission equipment according to claim 2, wherein the wavelength of the optical surveillance signal is 1.60 μm.
Priority Claims (1)
Number Date Country Kind
4-087247 Apr 1992 JP
Parent Case Info

This is a continuation of application Ser. No. 09/244,856 now U.S. Pat. No. 6,018,405 filed Feb. 5, 1998, which is a continuation of application Ser. No. 08/746,027 filed Nov. 5, 1996, U.S. Pat. No. 5,875,046, which is a continuation of application Ser. No. 08/705,366 filed Aug. 29, 1996, U.S. Pat. No. 5,812,289, which is a continuation of application Ser. No. 08/044,425 filed Apr. 7, 1993, U.S. Pat. No. 5,555,477, which is a continuation-in-part of application Ser. No. 08/023,546 filed Feb. 26, 1993, U.S. Pat. No. 5,500,756.

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Entry
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Continuations (4)
Number Date Country
Parent 09/244856 Feb 1998 US
Child 09/409872 US
Parent 08/746027 Nov 1996 US
Child 09/244856 US
Parent 08/705366 Aug 1996 US
Child 08/746027 US
Parent 08/044425 Apr 1993 US
Child 08/705366 US
Continuation in Parts (1)
Number Date Country
Parent 08/023546 Feb 1993 US
Child 08/044425 US