Patent Application
20170155981
This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2015-232622, filed on Nov. 30, 2015, the entire contents of which are incorporated herein by reference.
The embodiments discussed herein are related to an optical transmission device that transmits a wavelength division multiplexed optical signal and an optical transmission system.
In recent years, traffic in an access network that connects between a base station and a host station has been increasing with increasing mobile traffic. The host station can accommodate a plurality of base stations.
On the other hand, a PON (passive optical network) system has become widespread. The PON system is established in an ODN (optical distribution network), and can multicast a signal from a central station to a plurality of terminals. Thus, a configuration that realizes an access network for mobile traffic using an existing PON system has been proposed. Further, a configuration in which a wavelength division multiplexing (WDM) transmission is used for an access network for mobile traffic has also been proposed.
The baseband unit 1001 generates a signal to be transmitted to a base station, and processes a signal received from a base station. The optical line terminal 1002 converts a signal generated by the baseband unit 1001 into an optical signal, and converts an optical signal received from a base station into an electric signal. The passive splitter 1003 distributes an optical signal generated by the optical line terminal 1002 to a plurality of base stations, and guides optical signals received from a plurality of base stations to the optical line terminal 1002.
When a WDM transmission is used for the mobile access network of
The PON system for which a WDM technology is used is disclosed in, for example, Japanese Laid-open Patent Publication No. 2015-154399.
In the mobile access network described above, traffic in a certain area may increase. In this case, it is preferable that a plurality of base stations located in the certain area perform a coordinated multipoint (CoMP) transmission. The coordinated multipoint transmission is a technology adopted by the LTE-A (Long Term Evolution-Advanced), and a plurality of adjacent base stations transmit a signal to a terminal in a coordinated manner. Thus, the quality and/or the efficiency of a communication is improved in the cells of the plurality of base stations that perform a coordinated multipoint transmission. The shaded portion illustrated in
In this case, when a WDM transmission is used for a mobile access network, the host station 1000 transmits optical signals of different wavelengths with respect to a plurality of base stations. Further, the plurality of base stations transmit the optical signals of different wavelengths to the host station 1000. Then, when the area in which a coordinated multipoint transmission is moved, the allocation of wavelengths used between the host station 1000 and a plurality of coordination base stations is changed.
In order to change the allocation of a wavelength used between the host station 1000 and a base station, a control sequence is performed between the host station 1000 and each base station. For example, when each base station includes a wavelength tunable light source and a wavelength tunable filter, the host station 1000 reports, to each coordination base station, information that specifies a transmitter wavelength and a received wavelength. At this point, a negotiation is performed between the host station 1000 and each base station as needed.
This kind of negotiations may be necessary not only in a mobile access network in which a coordinated transmission is performed, but also in an optical transmission system in which an optical transmission device is connected to a plurality of remote devices.
According to an aspect of the embodiments, an optical transmission device transmits a WDM (wavelength division multiplexed) optical signal to a plurality of remote devices via an optical splitter and receives a plurality of optical signals from the plurality of remote devices via the optical splitter. The optical transmission device includes: a plurality of optical transceivers; a wavelength selective switch; and a controller configured to control the plurality of optical transceivers and the wavelength selective switch. Each of the optical transceivers includes a wavelength tunable light source. The controller controls, according to a wavelength of an optical signal received by a destination remote device that is specified from the plurality of remote devices, a wavelength of a wavelength tunable light source of a selected optical transceiver that is selected from the plurality of optical transceivers according to the destination remote device. The controller controls the wavelength selective switch so as to generate the WDM optical signal from a plurality of optical signals of different wavelengths generated by the plurality of optical transceivers using respective wavelength tunable light sources, and to guide the plurality of optical signals received from the plurality of remote devices to the plurality of optical transceivers according to wavelengths of the received plurality of optical signals.
The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention.
The host station 1 includes a plurality of baseband units (BBU) 11 and an optical line terminal (OLT) 12. Each baseband unit 11 generates a signal that is to be transmitted to a corresponding base station 2, and processes a signal received from the corresponding base station 2. The optical line terminal 12 includes a plurality of transceivers 13 and an optical circuit 14. In this example, one transceiver 13 is provided with respect to one baseband unit 11. Each transceiver 13 converts a signal generated from a corresponding baseband unit 11 into an optical signal, and converts an optical signal received from a corresponding base station 2 into an electric signal. Note that the transceiver 13 may perform a conversion of a format of a signal. The plurality of transceivers 13 generate optical signals of different wavelengths. The optical circuit 14 generates a WDM optical signal from a plurality of optical signals generated by the plurality of transceivers 13. Further, the optical circuit 14 guides a plurality of optical signals received from a network through the optical splitter 3 to corresponding transceivers 13 according to the wavelength.
The optical splitter 3 distributes a WDM optical signal transmitted from the host station 1 to the plurality of base stations 2. In other words, the same WDM optical signal is transmitted to the plurality of base stations 2. Further, the optical splitter 3 guides a plurality of optical signals received from the plurality of base stations 2 to the host station 1.
The base station 2 includes an optical network unit (ONU) 21 and a remote radio head (RRH) 22. The optical network unit 21 includes a transceiver, and can extract a target signal from a WDM optical signal received from the host station 1. Further, the optical network unit 21 can transmit an optical signal to the host station 1. The wavelengths of optical signals received by the respective baseband stations 2 (that is, received wavelengths) are different from one another. The wavelengths of optical signals transmitted from the respective baseband stations 2 to the host station 1 (that is, transmitter wavelengths) are also different from one another. The remote radio head 22 outputs a radio signal according to the target signal extracted by the optical network unit 21.
The host station 1 is an example of an optical transmission device. The baseband station 2 is an example of a remote device. The optical splitter 3 is an example of an optical splitter.
Here, it is assumed that a terminal 500 is located in an area in which the two cells overlap. In other words, it is assumed that a radio signal transmitted from the base station 2a and a radio signal transmitted from the base station 2b arrive at the terminal 500.
In such a case, the baseband units 11a and 11b transmit the same data in a coordinated manner. In other words, it is assumed that the data-a and the data-b illustrated in
The base stations 2a-2d include optical network units (ONU) 21a-21d, respectively. A transmitter Tx of each of the optical network units 21a-21d can transmit an optical signal to the host station 1 using a wavelength tunable light source. A transmitter wavelength of each of the optical network units 21a-21d is specified by, for example, the host station 1. Further, a receiver Rx of each of the optical network units 21a-21d can extract an optical signal of a target wavelength from a received WDM optical signal using a wavelength tunable BPF (band pass filter). A received wavelength of each of the optical network units 21a-21d is also specified by, for example, the host station 1.
It is assumed that a coordinated multipoint transmission of the base stations 2a and 2b is performed in the optical transmission system. Further, in order to perform a coordinated multipoint transmission, the baseband unit 11a transmits the data-a to the base station 2a, and the baseband unit 11b transmits the data-b to the base station 2b.
In this case, the optical network unit 21a of the base station 2a is set up such that it communicates with the transceiver 13a. In other words, the received wavelength of the receiver Rx of the optical network unit 21a is set to λ1. This permits the base station 2a to extract, from a received WDM optical signal, the data-a transmitted from the transceiver 13a. Further, the transmitter wavelength of the transmitter Tx of the optical network unit 21a is set to λ11. As a result, an optical signal transmitted from the base station 2a is guided by the AWG 15 to the transceiver 13a. Likewise, the optical network unit 21b of the base station 2b is set up such that it communicates with the transceiver 13b. In other words, the received wavelength of the optical network unit 21b is set to λ2. This permits the base station 2b to extract, from a received WDM optical signal, the data-b transmitted from the transceiver 13b. Further, the transmitter wavelength of the optical network unit 21b is set to λ12. As a result, an optical signal transmitted from the base station 2b is guided by the AWG 15 to the transceiver 13b.
It is assumed that, after that, the communication state is changed from a state in which the coordinated multipoint transmission between the base stations 2a and 2b is performed to a state in which a coordinated multipoint transmission between the base stations 2c and 2d is performed. In this case, the host station 1 changes the settings of the optical network units 21c and 21d such that a communication is performed between the transceiver 13a, 13b and the optical network unit 21c, 21d. Specifically, the optical network unit 21c of the base station 2c is set up such that it communicates with the transceiver 13a. In other words, the received wavelength of the optical network unit 21c is set to λ1. Further, the transmitter wavelength of the optical network unit 21c is set to λ11. Likewise, the optical network unit 21d of the base station 2d is set up such that it communicates with the transceiver 13b. In other words, the received wavelength of the optical network unit 21d is set to λ2. Further, the transmitter wavelength of the optical network unit 21d is set to λ12.
As described above, in the configuration illustrated in
However, it is preferable that a change in a base station that performs a coordinated multipoint transmission be realized without performing a control sequence between the host station and a corresponding base station. Thus, in the following descriptions, a configuration is described that makes it possible to change the base station which performs a coordinated multipoint transmission by performing a control in a host station.
In the first embodiment, a transmitter (Tx) 31 of each of the transceivers 13a-13d can transmit an optical signal using a wavelength tunable light source. The wavelengths of the wavelength tunable light sources of the transceivers 13a-13d are individually controlled by the controller 17. In other words, the wavelengths of optical signals transmitted by the transceivers 13a-13d are individually controlled by the controller 17. Further, each of the transceivers 13a-13d receives an optical signal guided from the wavelength selective switch 16.
In this example, the wavelength tunable light source of the transmitter 31 is driven by a data signal provided by a corresponding baseband unit 11. In other words, the transmitter 31 can generate a modulated optical signal by direct modulation. The optical signal generated by the transmitter 31 is guided to the wavelength selective switch 16. A receiver (Rx) 32 converts the optical signal guided by the wavelength selective switch 16 into an electric signal, and demodulates the electric signal to recover data.
In this example, each transceiver 13 (13a-13d) and the wavelength selective switch 16 are optically connected to each other by one optical fiber. In other words, an optical signal is transmitted in both directions through the one optical fiber. Here, the wavelength of an optical signal guided from the transceiver 13 to the wavelength selective switch 16, and the wavelength of an optical signal guided from the wavelength selective switch 16 to the transceiver 13 are different from each other. The transmitter 31 and the receiver 32 may be optically coupled to the wavelength selective switch 16 through an optical coupler.
The wavelength selective switch 16 includes an optical port P0 through which it is connected to a network, and optical ports P1-P4 through which it is respectively connected to the transceivers 13a-13d included in the host station 1. The wavelength selective switch 16 is able to individually control, according to a wavelength instruction given by the controller 17, the wavelengths received through the optical ports P1-P4 and the wavelengths output through the optical ports P1-P4. Further, the wavelength selective switch 16 is able to multiplex optical signals received through the optical ports P1-P4, so as to generate a WDM optical signal. This WDM optical signal is output to the network through the optical port P0. On the other hand, a plurality of optical signals input to the wavelength selective switch 16 through the optical port P0 are respectively output via the optical ports P1-P4.
The base stations 2a-2d include the optical network units 21a-21d, respectively. However, in the first embodiment, a transmitter (Tx) 33 of each of the optical network units 21a-21d transmits an optical signal to the host station 1 using a wavelength-fixed light source. Here, the transmitter wavelength of each of the optical network units 21a-21d is fixed in advance. Further, a receiver (Rx) 34 of each of the optical network units 21a-21d extracts an optical signal of a target wavelength from a received WDM optical signal using a wavelength-fixed bandpass filter.
In order to realize a coordinated multipoint transmission between the base stations 2a and 2b, the controller 17 controls the transceivers 13a and 13b and the wavelength selective switch 16 using wavelength instructions, such that a communication is performed between the baseband unit 11a, 11b and the base station 2a, 2b. The base station 2a receives an optical signal of the wavelength λ1. Thus, the controller 17 controls the transmitter wavelength of the transceiver 13a at λ1, and controls the received wavelength at the optical port P1 of the wavelength selective switch 16 at λ1, such that an optical signal transmitted from the transceiver 13a is received by the optical network unit 21a of the base station 2a. Further, the base station 2a transmits an optical signal of the wavelength λ11. Thus, the controller 17 controls the output wavelength at the optical port P1 of the wavelength selective switch 16 at λ11, such that an optical signal transmitted from the base station 2a is guided to the transceiver 13a. Likewise, the base station 2b receives an optical signal of the wavelength λ2. Thus, the controller 17 controls the transmitter wavelength of the transceiver 13b at λ2, and controls the received wavelength at the optical port P2 of the wavelength selective switch 16 at λ2, such that an optical signal transmitted from the transceiver 13b is received by the optical network unit 21b of the base station 2b. Further, the base station 2b transmits an optical signal of the wavelength λ12. Thus, the controller 17 controls the output wavelength at the optical port P2 of the wavelength selective switch 16 at λ12, such that an optical signal transmitted from the base station 2b is guided to the transceiver 13b.
When the configuration illustrated in
The transceiver 13a generates an optical signal λ1 that carries the data-a. The transceiver 13b generates an optical signal λ2 that carries the data-b. The wavelength selective switch 16 generates a WDM optical signal that includes the optical signal λ1 and the optical signal λ2. This WDM optical signal is distributed by the optical splitter 3 to the base stations 2a-2d.
The received wavelength of the base station 2a is λ1. Thus, the base station 2a extracts the optical signal λ1 from the received WDM optical signal so as to recover the data-a. The received wavelength of the base station 2b is λ2. Thus, the base station 2b extracts the optical signal λ2 from the received WDM optical signal so as to recover the data-b. Then, the base stations 2a and 2b perform a coordinated multipoint transmission using the recovered data.
The base station 2a transmits an optical signal λ11, and the base station 2b transmits an optical signal λ12. These optical signals are guided to the optical port P0 of the wavelength selective switch 16 through the optical splitter 3. At this point, the output wavelength at the optical port P1 of the wavelength selective switch 16 is set to λ11. Thus, the wavelength selective switch 16 selects the optical signal λ11 from among a plurality of optical signals input through the optical port P0, and outputs the selected optical signal through the optical port P1. As a result, the optical signal λ11 transmitted from the base station 2a is guided to the transceiver 13a. Likewise, the output wavelength at the optical port P2 of the wavelength selective switch 16 is set to λ12. Thus, the wavelength selective switch 16 selects the optical signal λ12 from among the plurality of optical signals input through the optical port P0, and outputs the selected optical signal through the optical port P2. As a result, the optical signal λ12 transmitted from the base station 2b is guided to the transceiver 13b.
It is assumed that, after that, the communication state is changed from a state in which the coordinated multipoint transmission between the base stations 2a and 2b is performed to a state in which a coordinated multipoint transmission between the base stations 2c and 2d is performed. In this case, as illustrated in
The base station 2c receives an optical signal of the wavelength λ3. Thus, the controller 17 controls the transmitter wavelength of the transceiver 13c at λ3, and controls the received wavelength at the optical port P1 of the wavelength selective switch 16 at λ3, such that an optical signal transmitted from the transceiver 13a is received by the optical network unit 21c of the base station 2c. Further, the base station 2c transmits an optical signal of the wavelength λ13. Thus, the controller 17 controls the output wavelength at the optical port P1 of the wavelength selective switch 16 at λ13, such that an optical signal transmitted from the base station 2c is guided to the transceiver 13a. Likewise, the base station 2d receives an optical signal of the wavelength λ4. Thus, the controller 17 controls the transmitter wavelength of the transceiver 13b at λ4, and controls the received wavelength at the optical port P2 of the wavelength selective switch 16 at λ4, such that an optical signal transmitted from the transceiver 13b is received by the optical network unit 21d of the base station 2d. Further, the base station 2d transmits an optical signal of the wavelength λ14. Thus, the controller 17 controls the output wavelength at the optical port P2 of the wavelength selective switch 16 at λ14, such that an optical signal transmitted from the base station 2d is guided to the transceiver 13b.
When the configuration illustrated in
The received wavelength of the base station 2c is λ3. Thus, the base station 2c extracts the optical signal λ3 from the received WDM optical signal so as to recover the data-a. The received wavelength of the base station 2d is λ4. Thus, the base station 2d extracts the optical signal λ4 from the received WDM optical signal so as to recover the data-b. Then, the base stations 2c and 2d perform a coordinated multipoint transmission using the recovered data.
The base station 2c transmits an optical signal λ13, and the base station 2d transmits an optical signal λ14. These optical signals are guided to the optical port P0 of the wavelength selective switch 16 through the optical splitter 3. At this point, the output wavelength at the optical port P1 of the wavelength selective switch 16 is set to λ13. Thus, the wavelength selective switch 16 selects the optical signal λ13 from among a plurality of optical signals input through the optical port P0, and outputs the selected optical signal through the optical port P1. As a result, the optical signal λ13 transmitted from the base station 2c is guided to the transceiver 13a. Likewise, the output wavelength at the optical port P2 of the wavelength selective switch 16 is set to λ14. Thus, the wavelength selective switch 16 selects the optical signal λ14 from among the plurality of optical signals input through the optical port P0, and outputs the selected optical signal through the optical port P2. As a result, the optical signal λ14 transmitted from the base station 2d is guided to the transceiver 13b.
As described above, in the optical transmission system according to the first embodiment, it is possible to change the base station which performs a coordinated multipoint transmission by changing the settings of the transceivers 13a-13d and the wavelength selective switch 16 in the host station 1. Thus, compared to the case of the configuration illustrated in
The optical line terminal 12 includes a plurality of transceivers 13 and the wavelength selective switch 16. As described above, the controller 17 controls the plurality of transceivers 13 and the wavelength selective switch 16. The BBU controller 18 controls the plurality of baseband units 11 when a coordinated multipoint transmission between base stations is performed. For example, when a plurality of base stations that perform a coordinated operation are specified, the BBU controller 18 selects a plurality of baseband units 11 that correspond to the specified plurality of base stations. Then, the BBU controller 18 instructs the selected baseband units 11 to generate data for a coordinated multipoint transmission. Further, the BBU controller 18 reports, to the controller 17, information that identifies the selected baseband unit 11. The controller 17 controls the transceivers 13 and the optical ports of the wavelength selective switch that correspond to the selected baseband unit 11 in accordance with the specified base stations that perform a coordinated operation.
In the configuration illustrated in
In the configuration illustrated in
When a coordinated multipoint transmission is performed in the optical transmission system illustrated in
As described above, when a plurality of transceivers 13 used for a coordinated multipoint transmission are connected to the same wavelength selective switch 16, the control time needed for changing the base station which performs a coordinated multipoint transmission is shorter. In other words, when the base station which performs a coordinated multipoint transmission is changed, the setting of the wavelength selective switch 16 is changed, as described with reference to
The configuration of the optical line terminal 12 is substantially the same in
In the configuration illustrated in
In S1, the BBU controller 18 selects a baseband unit to be used for performing a coordinated multipoint transmission. For example, when the host station 1 is instructed to start performing a coordinated multipoint transmission, the BBU controller 18 selects a baseband unit that operates for a target base station. Here, the number of baseband units to be selected is the same as the number of target base stations. When the baseband unit that operates for a target base station has been already selected, S1 is skipped. The baseband unit selected in S1 (or the baseband unit that has been selected previously) may hereinafter be referred to a “coordinated multipoint transmission (CoMP) baseband unit”.
In S2, the controller 17 identifies a received wavelength and a transmitter wavelength of each target base station. The received wavelength of a target base station corresponds to a transmission wavelength of a bandpass filter that is included in a receiver 34 of an optical network unit 21 of the target base station. The transmitter wavelength of a target base station corresponds to an oscillation wavelength of a wavelength-fixed light source that is included in a transmitter 33 of the optical network unit 21 of the target base station. It is assumed that management information that indicates the received wavelength and the transmitter wavelength of each of the base stations has been prepared and stored in advance in a memory in the host station 1.
In S3, the controller 17 controls the oscillation wavelength of a wavelength tunable light source of a transceiver 13 that corresponds to the CoMP transmission baseband unit such that the transmitter wavelength of the transceiver 13 matches the received wavelength of the target base station. In S4, the controller 17 controls the wavelength selective switch 16 such that the received wavelength at an optical port connected to the CoMP transmission baseband unit matches the received wavelength of the target base station. In S5, the controller 17 controls the wavelength selective switch 16 such that the output wavelength at the optical port connected to the CoMP transmission baseband unit matches the transmitter wavelength of the target base station.
The controller 17 and the BBU controller 18 are realized by, for example, a processor system that performs a given program. In this case, the processor system includes a processor element and a memory. The memory stores information for managing a transmitter wavelength and a received wavelength of each base station 2. The controller 17 and the BBU controller 18 may be realized by one processor system or by different processor systems.
In the optical transmission system according to the first embodiment, a communication is performed between a host station and a plurality of base stations. Here, it is preferable that, when a failure has occurred in the communication between the host station and the plurality of base stations, a cause of the failure (or a location in which the failure has occurred) be detected. Thus, an optical transmission system according to a second embodiment includes a function that detects a failure in a communication between a host station and a plurality of base stations.
As illustrated in
As described above, in the host station 1, the identification number (P1-P4) of each optical port of the wavelength selective switch 16 and the identification number (tone1-tone4) of a tone signal superimposed on an optical signal received through each of the optical ports are associated with each other. Further, at a base-station side, the location in which each base station is arranged, the transmitter wavelength (λ11-λ14) of each base station, and the identification number (tone11-tonel4) of a tone signal superimposed on an optical signal transmitted from each base station are associated with one another.
The optical splitter 41 splits an optical signal transmitted from the host station 1 to a plurality of base stations 2 and guides the optical signal to the optical coupler 43. The optical splitter 42 splits optical signals transmitted from the respective base stations 2 to the host station 1 and guides the optical signals to the optical coupler 43. The optical coupler 43 guides, to the tone signal detector 44, the optical signal guided from the optical splitter 41 and the optical signals guided from the optical splitter 42.
The tone signal detector 44 includes a photo detector that converts the optical signals guided from the optical coupler 43 into an electric signal. The tone signal detector 44 detects a tone signal from the electric signal generated by the photo detector. For example, the tone signal detector 44 performs an FFT operation on the electric signal generated by the photo detector, so as to obtain a frequency domain signal that indicates a spectrum of a frequency band in which a tone signal is allocated. Then, the status decision unit 45 detects a failure in the optical transmission system according to the frequency domain signal. Note that the status decision unit 45 may decide the status in the optical transmission system according to whether a tone signal superimposed on each optical signal is detected.
An example of a method for detecting a failure in the optical transmission system is described with reference to
When a failure does not occur in the optical transmission system, all of the tone signals are detected by the tone signal detector 44. Thus, when the spectrum illustrated in
When a branch line between the optical splitter 3 and a base station 2 is broken, a tone signal corresponding to the branch line is not detected. Thus, when the spectrum illustrated in
When a circuit between the host station 1 and the optical splitter 3 (that is, a transmission link common to ONU1-ONU4) is broken, none of the tone signals tonell-tonel4 are detected. Thus, when the spectrum illustrated in
In S12, the status decision unit 45 decides whether the tone signal of ONU1 is lost according to an output signal of the tone signal detector 44. When the tone signal of ONU1 is lost, the status decision unit 45 confirms, in S13, whether all of the tone signals of ONU1-ONU4 are lost. When all of the tone signals of ONU1-ONU4 are lost, the status decision unit 45 decides that a failure has occurred in a common transmission link between the host station 1 and ONU1-ONU4. On the other hand, when at least one of the tone signals of ONU1-ONU4 is detected, the status decision unit 45 decides, in S15, that ONU1 has broken down or that a failure has occurred in a transmission link between the optical splitter 3 and ONU1.
When there exists the tone signal of ONU1 (S12: No), the status decision unit 45 decides whether the tone signal of the transceiver 13a is lost. When the tone signal of the transceiver 13a is lost, the status decision unit 45 confirms, in S17, whether all of the tone signals of the transceivers 13a-13d are lost. When all of the tone signals of the transceivers 13a-13d are lost, the status decision unit 45 decides, in S18, that the wavelength selective switch 16 has broken down. On the other hand, when at least one of the tone signals of the transceivers 13a-13d is detected, the status decision unit 45 decides, in S19, that an optical port (the port P1 in
When the tone signal of ONU1 is detected and the tone signal of the transceiver 13a is also detected (S16: No), the status decision unit 45 decides, in S20, that the wavelength allocation to an optical port of the wavelength selective switch 16 connected to the transceiver 13a is not correct.
As described above, the status decision unit 45 monitors a tone signal superimposed on each optical signal, so as to identify or estimate a location in which a failure has occurred in an optical transmission system. The failure detection described above may be realized by monitoring a spectrum of a main data signal of each optical channel by use of an OMC (optical channel monitor). However, the OMC is expensive. On the other hand, in the second embodiment, an optical signal is converted into an electric signal by a photo detector such as a photo diode, and a spectrum of the electric signal is monitored, so as to realize a failure detection. In other words, according to the second embodiment, it is possible to realize a failure detection in an inexpensive configuration.
The status decision unit 45 is realized by, for example, a processor system that executes a given program. In this case, the processor system includes a processor element and a memory. This processor system may provide a portion of the function (that is, an FFT operation) of the tone signal detector 44.
The configuration according to the second embodiment can detect not only a failure in an optical transmission system but also an operational status of the optical line terminal (OLT) 12. A function that detects an operational status of the optical line terminal 12 is described below with reference to
In the example of
After that, the host station 1 performs a switching operation below:
In this case, first, the controller 17 changes the received wavelength at the optical port P1 of the wavelength selective switch 16 from λ1 to λ3 such that the received wavelength at an optical port to which the transceiver 13a is connected is the same as the received wavelength of ONU3. At this point, the transceiver 13a transmits an optical signal of the wavelength λ1. Thus, the optical port P1 of the wavelength selective switch 16 blocks the optical signal transmitted from the transceiver 13a. As a result, when the spectrum illustrated in
Next, the controller 17 changes the transmitter wavelength of the transceiver 13a from λ1 to λ3 such that the transmitter wavelength of the transceiver 13a is the same as the received wavelength of ONU3. At this point, the received wavelength at the optical port P1 of the wavelength selective switch 16 is λ3. Thus, the wavelength selective switch 16 guides, from the optical port P1 to the optical port P0, an optical signal λ3 transmitted from the transceiver 13a. In this case, the tone signal tone1 superimposed on the optical signal λ3 is detected by the tone signal detector 44. Thus, when the spectrum illustrated in
Further, the controller 17 sets the received wavelength at the optical port P3 of the wavelength selective switch 16 to λ1, such that the received wavelength at an optical port to which the transceiver 13c is connected is the same as the received wavelength of ONU1. At this point, the transceiver 13c has not transmitted an optical signal yet. Thus, the spectrum illustrated in
All examples and conditional language provided herein are intended for the pedagogical purposes of aiding the reader in understanding the invention and the concepts contributed by the inventor to further the art, and are not to be construed as limitations to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although one or more embodiments of the present inventions have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-232622 | Nov 2015 | JP | national |
