Patent Application
20210359764
The present invention relates to an optical transmitter and an optical receiver, and more particularly relates to an optical transmitter and an optical receiver for wavelength-multiplexing a main signal and a control signal for transmission, an optical transmitting method, and an optical receiving method.
In a wavelength multiplexing optical transmission system of recent years, a new modulation method and forward error correction (FEC) have been introduced. By adoption of a flexible grid and introduction of optical add-drop multiplexing (OADM), a configuration of an optical signal to be accommodated in an optical line has become very complicated.
There is ITU-T Recommendation G.694.1, as international standards relating to the flexible grid. In this recommendation, a smallest channel interval on a wavelength grid is 12.5 GHz. A main signal is wavelength-multiplexed at an interval of an integer multiple of 12.5 GHz (25 GHz, 50 GHz, and the like). It is possible to determine a bandwidth of a main signal according to a transmission speed or a modulation method. ITU-T is an abbreviation of International Telecommunication Union Telecommunication Standardization Sector. In association with the present invention, PTL 1 describes a configuration in which a main signal and a control signal are multiplexed for transmission.
[PTL 1] Japanese Unexamined Patent Application Publication No. 2006-197489
In an optical transmission system, it is necessary to accurately set, in an optical transmission device, a plurality of parameters relating to a main signal at a time of installing the optical transmission device (e.g., an optical transmitter and an optical receiver), or at a time of adding a wavelength of an optical signal. At this occasion, a worker who installs the optical transmitter and a worker who installs the optical receiver need to accurately set these parameters in order to enable a main signal to be transmitted between the optical transmitter and the optical receiver opposing to each other. At a time of changing specifications such as adding a wavelength of a main signal, the worker of the optical transmitter and the worker of the optical receiver also need to change the parameters, while communicating with each other. Therefore, in a general optical transmission device, there is a problem that setting parameters in an optical transmitter and an optical receiver opposing to each other is cumbersome.
An object of the present invention is to enable a function of an optical receiver to be set from an optical transmitter with a simple configuration.
An optical transmitter according to the present invention includes: a first transmitting means for generating a first optical signal including a main signal; a second transmitting means for generating a second optical signal including a control signal; and a first multiplexing means for generating a channel signal in which the second optical signal is wavelength-multiplexed at one end of a wavelength band of the first optical signal.
An optical receiver according to the present invention includes: a first demultiplexing means for demultiplexing, from a received channel signal, a first optical signal including a main signal, and a second optical signal being wavelength-multiplexed at one end of a wavelength band of the first optical signal and including a control signal; a first receiving means for being controlled based on the control signal and demodulating a main signal from the first optical signal; and a second receiving means for demodulating the control signal from the second optical signal.
An optical transmitting method according to the present invention includes a procedure of generating a first optical signal including a main signal; generating a second optical signal including a control signal; and generating a channel signal in which the second optical signal is wavelength-multiplexed at one end of a wavelength band of the first optical signal.
An optical receiving method according to the present invention includes: a procedure of demultiplexing, from a received channel signal, a first optical signal including a main signal, and a second optical signal being wavelength-multiplexed at one end of a wavelength band of the first optical signal and including a control signal; demodulating the control signal from the second optical signal; and demodulating a main signal from the first optical signal, based on the control signal.
The present invention enables a function of an optical receiver to be set from an optical transmitter with a simple configuration.
(Description on WDM Transmitting Device 1)
The WDM transmitting device 1 includes k (where k is a natural number) optical transmitters 11 to 1k, and a wavelength multiplexing circuit 120. The optical transmitter 11 to 1k is capable of generating a variety of optical transmission signals by a parameter to be set according to a performance required in the optical transmission system 10. In the present example embodiment, an optical signal transmitting function included in the optical transmitter 11 to 1k is described. Alternatively, the optical transmitter 11 to 1k may be a transponder (optical transceiver) further having a receiving function similar to an optical receiver 21 to 2k to be described later.
The optical transmitter 11 to 1k generates an optical signal including a control signal and a main signal. The main signal is a signal for transmitting user's data in the optical transmission system 10. The control signal is a signal for transmitting a parameter for controlling the WDM receiving device 2 from the WDM transmitting device 1.
Each of the optical transmitters 11 to 1k includes a main signal transmission circuit 101, a control circuit 111, a control signal transmission circuit 112, and a multiplexer 102. The main signal transmission circuit 101 converts a main signal into an optical signal suitable for wavelength multiplexing optical transmission, based on a parameter set by the control circuit 111, and outputs the optical signal. Hereinafter, the optical signal to be output from the main signal transmission circuit 101 is referred to as a “main optical signal”. The main signal transmission circuit 101 is an electro-photo conversion circuit, and may include an optical modulator. The main signal transmission circuits 101 of the optical transmitters 11 to 1k respectively generate optical signals having wavelengths from λ1 to λk. Bandwidths of main optical signals to be output from the optical transmitters 11 to 1k are not necessarily the same, and do not overlap one another.
The control circuit 111 is an electric circuit for setting a parameter in the main signal transmission circuit 101 and generating a control signal including a parameter to be notified to an optical receiver opposing to an optical transmitter. The control circuit 111 controls the main signal transmission circuit 101, for example, by setting, in the main signal transmission circuit 101, a parameter for specifying a wavelength, a band, a modulation method, and the like of a main optical signal. Both of a parameter to be set in the main signal transmission circuit 101 and a parameter to be notified to an opposing optical receiver are determined in such a way that an optical transmitter and the optical receiver are communicable to each other. These parameters may differ from each other. A parameter to be notified to an optical receiver is, for example, information for setting a wavelength, a band, a modulation method, and the like of a main optical signal to be received with respect to the main signal reception circuit 201.
The control signal transmission circuit 112 converts a control signal notified from the control circuit 111 into an optical signal. Specifically, the control signal transmission circuit 112 is also an electro-photo conversion circuit. Hereinafter, an optical signal to be output from the control signal transmission circuit 112 is referred to as a “control optical signal”. The multiplexer 102 generates an optical signal (hereinafter, referred to as a “channel signal”) in which a main optical signal output from the main signal transmission circuit 101, and a control optical signal output from the control signal transmission circuit 112 are multiplexed, and outputs the channel signal to a wavelength multiplexing circuit 120. Each of the optical transmitters 11 to 1k has the above-described function of outputting a channel signal. Channel signals to be generated by the optical transmitters 11 to 1k are respectively discriminated as signals in which channels are different from one another.
The wavelength multiplexing circuit 120 generates a WDM signal by wavelength multiplexing channel signals generated by the optical transmitters 11 to 1k, and outputs the WDM signal to the transmission path 3. Causing the wavelength multiplexing circuit 120 to have a function of the multiplexer 102 enables the multiplexer 102 to be omitted from the optical transmitter 11 to 1k. One or both of the wavelength multiplexing circuit 120 and the multiplexer 102 may be a coupler.
(Description on WDM Receiving Device 2)
The WDM receiving device 2 receives a WDM signal from the transmission path 3. The WDM receiving device 2 includes a wavelength separation circuit 220 and k optical receivers 21 to 2k. The wavelength separation circuit 220 separates a WDM signal received from the transmission path 3 for each channel (specifically, into a channel signal). The optical receivers 21 to 2k receive optical signals of wavelengths from λ1 to λk. Channel signals separated by the wavelength separation circuit 220 are associated with channel signals before being wavelength-multiplexed by the wavelength multiplexing circuit 120.
The optical receiver 21 to 2k is capable of receiving a variety of optical signals by setting a parameter. In the present example embodiment, an optical signal receiving function included in the optical receiver 21 to 2k is described. The optical receiver 21 to 2k may be a transponder having a transmitting function similar to the optical transmitter 11 to 1k.
The optical receiver 21 to 2k includes a main signal reception circuit 201, a demultiplexer 202, a control circuit 211, and a control signal reception circuit 212. The demultiplexer 202 demultiplexes a channel signal separated by the wavelength separation circuit 220 for each channel (specifically, for each wavelength) into a main optical signal and a control optical signal. The main signal reception circuit 201 demodulates a main signal from the main optical signal, and outputs the main signal to the outside of the WDM receiving device 2. The control signal reception circuit 212 demodulates a control signal from the control optical signal, and outputs the control signal to the control circuit 211. The control circuit 211 extracts a parameter from the control signal. The extracted parameter is a parameter included in a control signal generated by the control circuit 111 of an optical transmitter that transmits a received channel signal. Then, the control circuit 211 controls the main signal reception circuit 201, based on the extracted parameter.
In this way, a parameter for setting a function of the main signal reception circuit 201 is transmitted from the optical transmitter 11 to 1k to the optical receiver 21 to 2k for receiving the channel signal. Consequently, in the optical transmission system 10, it is possible to automatically perform, from the WDM transmitting device 1, parameter setting with respect to the optical receiver 21 to 2k of the WDM receiving device 2, without disposing a worker at the WDM receiving device 2.
The demultiplexer 202 may directly demultiplex a WDM signal into a main optical signal and a control optical signal of a channel to be received by an optical receiver included in the demultiplexer 202. In this case, it is possible to omit the wavelength separation circuit 220 from the WDM receiving device 2. Alternatively, the wavelength separation circuit 220 may further have a function of the demultiplexer 202. In this case, the wavelength separation circuit 220 outputs, to the optical receivers 21 to 2k, an optical signal in which a main optical signal and a control optical signal are separated.
(Description on Operation of Optical Transmission System 10)
Next, an operation of the optical transmission system 10 is described in more detail by taking an example of transmission from an optical transmitter 11 to an optical receiver 21. The main signal transmission circuit 101 included in the optical transmitter 11 is capable of switching a function such as a wavelength, a bandwidth, a transmission speed, and a modulation method of a main optical signal. The control circuit 111 generates a parameter for use in switching among these functions, and sets the parameter in the main signal transmission circuit 101. Information for generating a parameter may be input from the outside of the WDM transmitting device 1 to the control circuit 111. Information for generating a parameter may be changed at any time. The control circuit 111 generates a control signal including a parameter to be set in the main signal reception circuit 201 in association with these functions, and outputs the control signal to the control signal transmission circuit 112. The control signal is a transmittable electrical signal, and, for example, an asynchronous serial digital signal.
The control signal transmission circuit 112 converts a control signal input from the control circuit 111 into a control optical signal. The control optical signal is an optical signal, and a wavelength thereof depends on a wavelength band of a main optical signal to be generated by the main signal transmission circuit 101. In the present example embodiment, a wavelength of a control optical signal is set at an end (an upper end or a lower end) of a wavelength band of a main optical signal. A main optical signal to be output from the main signal transmission circuit 101 and a control optical signal to be output from the control signal transmission circuit 112 are multiplexed by the multiplexer 102, and the multiplexed signal is output to the wavelength multiplexing circuit 120, as one channel signal.
The optical transmitter 12 to 1k also performs an operation similar to the optical transmitter 11. A wavelength band of a channel signal (specifically, an optical signal in which a main optical signal and a control optical signal are wavelength-multiplexed) to be output from each of the optical transmitters 11 to 1k is set in such a way as not to overlap one another. The wavelength multiplexing circuit 120 wavelength-multiplexes a channel signal to be output from the optical transmitter 11 to 1k, and transmits the signal to a transmission path as a WDM signal.
A channel signal and a WDM signal are described with reference to
Specifically, when a main optical signal having the wavelength band in
Both of a bandwidth and a central frequency interval of a main optical signal included in each channel signal in
A control optical signal is transmitted together with a main optical signal as a part of a channel signal. The wavelength separation circuit 220 separates the WDM signal in
The demultiplexer 202 included in the optical receiver 21 demultiplexes a channel signal input from the wavelength separation circuit 220 to the optical receiver 21 into a control optical signal and a main optical signal. The control signal reception circuit 212 demodulates a control signal from the demultiplexed control optical signal. The control circuit 211 receives the control signal from the control signal reception circuit 212, and extracts a parameter from the control signal. The parameter to be extracted is a parameter generated by the control circuit 111, and set in the main signal reception circuit 201. By causing the main signal reception circuit 201 to set the extracted parameter, the control circuit 211 controls the main signal reception circuit 201. In the main signal reception circuit 201, a main optical signal receiving function is achieved based on the set parameter. The main signal reception circuit 201 demodulates a main signal from the main optical signal demultiplexed by the demultiplexer 202. The demodulated main signal may be output to another transmission device connected to the outside of the WDM receiving device 2. The optical receiver 22 to 2k also performs an operation similar to the optical receiver 21.
Preferably, a level of a control optical signal with respect to a main optical signal may be set low in order to further reduce an influence of the control optical signal on transmission quality of the main optical signal. In this case, it is necessary for the control signal reception circuit 212 to detect a control optical signal of low power, as compared with a main optical signal. Since a frequency band of a control optical signal is sufficiently narrow, as compared with a frequency band of a main optical signal, the control signal reception circuit 212 is capable of receiving the control optical signal with high sensitivity by employing a narrow band filter. Since a control optical signal is present at a lower end of a spectrum of a main optical signal, the main signal reception circuit 202 may receive the control optical signal as noise in a band other than the band of a main signal. In this case, in the main signal reception circuit 201, a control optical signal is removed by an equalization filter, without greatly affecting transmission quality of a main optical signal.
As described above, by transmitting a main optical signal and a control optical signal as one channel signal, it is possible to transmit a parameter generated by the optical transmitter 11 to 1k to the optical receiver 21 to 2k with a simple configuration. Consequently, the optical transmission system 10 according to the present example embodiment enables a function of an optical receiver to be set from an optical transmitter with a simple configuration.
The WDM receiving device 2A is different from the WDM receiving device 2 in a point that a monitoring circuit 41 is included. A wavelength separation circuit 220A included in the WDM receiving device 2A splits a WDM signal with a predetermined split ratio, and inputs the signal to the monitoring circuit 41. The monitoring circuit 41 includes a control circuit 411 and a control signal reception circuit 412.
The control signal reception circuit 412 is a photoelectric conversion circuit equipped with an optical filter. The control signal reception circuit 412 receives a control optical signal included in a WDM signal input from the wavelength separation circuit 220A. When a WDM signal includes a multicarrier signal, a position of a boundary of each channel signal is not fixed. Therefore, in the control signal reception circuit 412, there is a case that it is difficult to identify each channel only by a spectrum of a WDM signal. In view of the above, the control signal reception circuit 412 has a wavelength variable optical band-pass filter. By causing the wavelength variable optical band-pass filter to sweep a wavelength that passes in a narrow band, it is possible to detect only a control optical signal for each channel. Consequently, it is possible to identify a control optical signal included in a WDM signal, and acquire a bandwidth and a parameter of a channel signal for each channel. The control signal reception circuit 412 demodulates, from the identified control optical signal, a control signal included in each of the control optical signals. The demodulated control signal is output to the control circuit 411.
The control circuit 411 extracts, from each of the demodulated control signals, a parameter for each channel signal. The control circuit 411 may acquire, from a wavelength of a detected control optical signal, information on the number of channel signals included in a WDM signal, and a bandwidth of a main optical signal of each of the channel signals. The control circuit 411 stores information such as an extracted parameter and a bandwidth of a main optical signal. The control circuit 411 may control a function of the optical receiver 21 to 2k, based on the parameter. In the optical transmission system 20 having the above-described configuration, an optical receiver of a channel capable of receiving a control optical signal by the monitoring circuit 41 does not have to include the control signal reception circuit 212 and the control circuit 211, and it is possible to simplify a configuration of the optical receiver. When the monitoring circuit 41 is capable of detecting control optical signals of all channel signals to be received by the WDM receiving device 2A, the optical receiver 21 to 2k does not have to include the control signal reception circuit 212 and the control circuit 211.
Alternatively, the optical receiver 21 to 2k may receive control from any one of the control circuit 211 and the control circuit 411. In this case, a parameter extraction function of the optical transmission system 20 is made redundant.
The optical receiver 60 having the above-described configuration receives an optical signal in which a first optical signal including a main signal, and a second optical signal including a control signal are wavelength-multiplexed. Since the second optical signal is wavelength-multiplexed at one end of a wavelength band of the first optical signal, the optical receiver 60 is capable of receiving the first and second optical signals as a same channel signal. Therefore, the optical receiver 60 is capable of setting a function of the optical receiver 60 with a simple configuration by using a control signal generated by an optical transmitter.
The example embodiments according to the present invention may also be described as the following supplementary notes, but are not limited to these supplementary notes.
(Supplementary Note 1)
An optical transmitter including:
a first transmitting means for generating a first optical signal including a main signal;
a second transmitting means for generating a second optical signal including a control signal; and
a first multiplexing means for generating a channel signal in which the second optical signal is wavelength-multiplexed at one end of a wavelength band of the first optical signal.
(Supplementary Note 2)
The optical transmitter according to supplementary note 1, wherein the control signal includes a parameter for use in setting a function of an optical receiver that receives the channel signal.
(Supplementary Note 3)
The optical transmitter according to supplementary note 1 or 2, wherein
a band of the second optical signal is narrower than a band of the first optical signal.
(Supplementary Note 4)
The optical transmitter according to any one of supplementary notes 1 to 3, wherein
peak power of the second optical signal is smaller than peak power of the first optical signal.
(Supplementary Note 5)
The optical transmitter according to any one of supplementary notes 1 to 4, wherein
the first optical signal is a multicarrier signal.
(Supplementary Note 6)
The optical transmitter according to any one of supplementary notes 1 to 5, wherein
at least one of a central frequency and a bandwidth of the first optical signal complies with International Telecommunication Union Telecommunication Standardization Sector (ITU-T) Recommendation G.694.1.
(Supplementary Note 7)
A wavelength multiplexing transmitting device including:
a plurality of the optical transmitters according to any one of supplementary notes 1 to 6 that output the channel signals in which wavelength bands do not overlap each other; and
a second multiplexing means for multiplexing channels to be output from a plurality of the optical transmitters, and outputting a wavelength-multiplexed signal.
(Supplementary Note 8)
An optical receiver including:
a first demultiplexing means for demultiplexing, from a received channel signal, a first optical signal including a main signal, and a second optical signal being wavelength-multiplexed at one end of a wavelength band of the first optical signal and including a control signal;
a first receiving means, being controlled based on the control signal, for demodulating a main signal from the first optical signal; and
a second receiving means for demodulating the control signal from the second optical signal.
(Supplementary Note 9)
The optical receiver according to supplementary note 8, wherein
the control signal includes a parameter for use in setting a function of the first receiving means.
(Supplementary Note 10)
The optical receiver according to supplementary note 8 or 9, wherein
the first demultiplexing means demultiplexes, from the channel signal, the second optical signal by using an optical filter having a band narrower than a band of the first optical signal.
(Supplementary Note 11)
The optical receiver according to any one of supplementary notes 8 to 10, wherein
the first optical signal is a multicarrier signal.
(Supplementary Note 12)
The optical receiver according to any one of supplementary notes 8 to 11, wherein
at least one of a central frequency and a bandwidth of the first optical signal complies with ITU-T Recommendation G.694.1.
(Supplementary Note 13)
A wavelength multiplexing receiving device including:
a second demultiplexing means for demultiplexing a wavelength-multiplexed signal in which a plurality of the channel signals are wavelength-multiplexed, and outputting a plurality of the channel signals; and
a plurality of the optical receivers according to any one of supplementary notes 8 to 12 that receive the demultiplexed channel signals.
(Supplementary Note 14)
The wavelength multiplexing receiving device according to supplementary note 13, further including
a monitoring means for extracting, from the wavelength-multiplexed signal, a plurality of parameters being associated with the plurality of channel signals, and setting the extracted parameters in the first receiving means.
(Supplementary Note 15)
An optical transmission system in which the wavelength multiplexing transmitting device according to supplementary note 7, and the wavelength multiplexing receiving device according to supplementary note 13 or 14 are communicably connected by a transmission path.
(Supplementary Note 16)
A transponder including the optical transmitter according to any one of supplementary notes 1 to 5, and the optical receiver according to any one of supplementary notes 8 to 12.
(Supplementary Note 17)
An optical transmitting method including:
generating a first optical signal including a main signal;
generating a second optical signal including a control signal; and
generating a channel signal in which the second optical signal is wavelength-multiplexed at one end of a wavelength band of the first optical signal.
(Supplementary Note 18)
An optical receiving method including:
demultiplexing, from a received channel signal, a first optical signal including a main signal, and a second optical signal being wavelength-multiplexed at one end of a wavelength band of the first optical signal and including a control signal;
demodulating the control signal from the second optical signal; and
demodulating a main signal from the first optical signal, based on the control signal.
While the invention has been particularly shown and described with reference to example embodiments thereof, the invention is not limited to these example embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirt and scope of the present invention as defined by the claims.
Further, configurations described in the example embodiments are not necessarily exclusive to one another. An operation and an advantageous effect of the present invention may be achieved by a configuration in which all or a part of the above-described example embodiments are combined.
Functions of the WDM transmitting device 1, the WDM receiving device 2, and the WDM receiving device 2A described in the above-described example embodiments may be achieved by causing a central processing unit (CPU) provided in each of the devices to execute a program. The program is recorded in a fixed non-transitory recording medium. As the recording medium, a semiconductor memory or a fixed magnetic disk device is used. However, the recording medium is not limited to these devices. The CPU is, for example, a computer included in the control circuit 111, 211, or 411. The CPU may be provided outside of the control circuit 111, 211, or 411.
This application is based upon and claims the benefit of priority from Japanese patent application No. 2018-181820, filed on Sep. 27, 2018, the disclosure of which is incorporated herein in its entirety by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-181820 | Sep 2018 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/036867 | 9/20/2019 | WO | 00 |
