JP2018198395A - Photoreceiver - Google Patents

Abstract

To provide a photoreceiver that can make a flexible response to changes of the characteristics of a reception signal while ensuring the quality of the reception signal.SOLUTION: The photoreceiver includes: a local oscillator for outputting a local oscillation light with a specific wavelength; a coherent reception unit for selectively receiving an optical signal with a specific wavelength from a wavelength multiplex optical signal by causing the wavelength multiplex optical signal to interfere with the local oscillation light; a light reception unit for converting the optical signal selectively received by the coherent reception unit into an electric signal; and a signal processing unit for processing the electric signal and outputting the signal as an output signal in a reception band according to the characteristics of the light signal selectively received by the coherent reception unit.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an optical receiver and an optical reception method.

  An optical communication system is required to have a large capacity with an increase in communication volume, and has been accelerated by a digital coherent technique or a multi-level modulation method. In recent years, in addition to these increases in capacity, in addition to switching wavelengths and paths according to the situation, combining multiple symbol rates and modulation methods, or changing them flexibly, from the viewpoint of communication resource utilization efficiency It has been required. In order to realize a flexible optical communication system, not only a single symbol rate and modulation scheme but also an optical transceiver corresponding to a plurality of symbol rates and modulation schemes are required for digital coherent optical transceivers. .

  On the other hand, in recent optical communication systems, a wavelength division multiplexing (WDM) transmission system in which a plurality of wavelengths are bundled and transmitted is the mainstream. In a digital coherent optical communication system, a local signal light having a frequency very close to the carrier frequency of a desired optical signal is combined from wavelength multiplexed optical signals (hereinafter referred to as “WDM signals”) simultaneously received by an optical receiver. By making waves interfere with each other, it is possible to extract a desired optical signal.

  In relation to the present invention, Patent Document 1 and Patent Document 2 describe systems for transmitting WDM signals.

JP 2017-028451 JP2015-019284A

  Here, in the receiver, when the frequency bandwidth for processing the received signal is not sufficiently small with respect to the channel interval of the WDM signal, the quality of the received signal is reduced by crosstalk with the adjacent channel at the time of wavelength selective reception by coherent detection. There is a possibility of degrading.

FIG. 14 is a diagram illustrating an example of a relationship between a channel interval of a WDM signal and a reception band. In Figure 14, the horizontal axis frequency, indicating the channel of the optical signal 821 to 823 included in the WDM signal frequency _{f x,} with _{f x + 1, f x-} 1. A broken line is a spectrum of the optical signals 821 to 823, and the spectrum has a width depending on the symbol rate. If the optical signals 822 and 823 of the adjacent channels have the same symbol rate as the optical signal 821, the optical signals 822 and 823 have the same spectral width as the optical signal 821. Therefore, the optical signals 821 to 823 are accommodated in the WDM channel slots having the same width. Further, the channel spacing when the optical signals 821 to 823 are wavelength-multiplexed is densely arranged in a range that does not interfere with the spectrum of the adjacent optical signal. In the receiver that receives the optical signal 821, only the optical signal 821 within the band is processed by the band-pass filter having the bandwidth indicated by the reception band BW1.

  FIG. 15 is another diagram illustrating an example of a relationship between a channel interval of a WDM signal and a reception band. The symbol rate of the optical signals 831 to 833 is lower than the symbol rate of the optical signals 821 to 823. Since the bandwidth occupied by the spectrum of the optical signal depends on the symbol rate, the symbol rates of the optical signals 831 to 833 in FIG. 15 are lower than those of the optical signals 821 to 823 in FIG. As a result, the spectral width of the optical signal 831 and the optical signals 832 and 833 of the adjacent channels becomes narrower, and the width and channel spacing of the WDM channel slot also become narrower than those in FIG. At this time, since the bandwidth BW1 of the receiver is wider than the bandwidth of the optical signal 831, when the optical signal 831 is received, a part of the spectrum of the optical signals 832 and 833 of the adjacent channels is also received. Therefore, the reception quality of the optical signal 831 is deteriorated due to crosstalk with these signals.

In this way, in a general WDM signal receiver, the relationship between the bandwidth of the received signal and the channel interval changes due to changes in the received signal characteristics such as the symbol rate and modulation method of the WDM signal, and the quality of the received signal Degradation may occur.
(Object of invention)
An object of the present invention is to provide an optical receiver that can flexibly cope with a change in characteristics of a received optical signal while ensuring the quality of the received signal.

The optical receiver of the present invention is
Local oscillation means for outputting local oscillation light of a predetermined wavelength;
Coherent receiving means for selectively receiving the optical signal of the predetermined wavelength from the wavelength multiplexed optical signal by causing the wavelength multiplexed optical signal to interfere with the local oscillation light;
A light receiving means for converting the optical signal selectively received by the coherent receiving means into an electrical signal;
Signal processing means for processing the electrical signal and outputting it as an output signal in a reception band according to the characteristics of the optical signal selectively received by the coherent receiving means;
Is provided.

The optical receiving method of the present invention includes:
Outputs local oscillation light of a predetermined wavelength,
Selectively receiving the optical signal of the predetermined wavelength from the wavelength multiplexed optical signal by causing the wavelength multiplexed optical signal to interfere with the local oscillation light;
Selectively converting the received optical signal into an electrical signal;
Processing the electrical signal in a reception band according to the characteristics of the optical signal selectively received;
Includes procedures.

  The present invention can provide an optical receiver that can flexibly cope with a change in characteristics of a received optical signal while ensuring the quality of the received signal.

1 is a diagram illustrating a configuration example of an optical communication system 1. FIG. 2 is a diagram illustrating a configuration example of an optical receiver 201. FIG. FIG. 11 is a sequence diagram illustrating an operation example of the optical receiver 201. It is a figure which shows the example of the relationship between the channel space | interval and reception band of a WDM signal. It is a figure which shows the structural example of 201 A of optical receivers. It is an example of the table for setting a receiving band with a control signal. It is a sequence diagram explaining an example of operation of optical receiver 201A. It is a figure which shows the structural example of the optical receiver 201B. It is a sequence diagram explaining the operation example of the optical receiver 201B. It is a figure explaining the example of the setting of the receiving band based on quality information. It is a figure which shows the structural example of 201 C of optical transceivers. It is a table | surface which shows the example of the setting content to each part of the optical transceiver 201C by a control signal. It is a sequence diagram explaining an example of operation of optical transceiver 201C. It is a figure which shows the example of the relationship between the channel space | interval and reception band of a WDM signal. It is another figure which shows the example of the relationship between the channel space | interval of a WDM signal, and a receiving band.

  Hereinafter, embodiments of the present invention will be described. The arrows between the blocks attached to the drawings referred to in each embodiment show examples of the signal directions between the blocks, and do not limit the signal directions.

(First embodiment)
FIG. 1 is a diagram showing a configuration example of an optical communication system 1 according to the first embodiment of the present invention. The optical communication system 1 includes optical communication devices 11 to 1N (N is an integer of 2 or more), optical communication devices 21 to 2N, couplers 31 and distributors 32, optical amplifiers (Amplifiers) 41 and 42, and optical fiber transmission. Road 51 is provided. The optical communication apparatuses 11 to 1N have channels indicated by ch 1 to ch N, convert input electric signals into optical signals, and transmit the optical signals through the respective channels. In the present embodiment, the wavelengths of ch 1 to ch N are different. The coupler 31 combines the ch 1 to ch N optical signals output from the optical communication apparatuses 11 to 1 N to generate a WDM signal, and sends the WDM signal to the optical fiber transmission line 51. As the coupler 31, an N × 1 star coupler, a multiplexer, or a wavelength selecting switch (WSS) can be used. The optical fiber transmission line 51 includes optical amplifiers 41 and 42, and amplifies the propagating WDM signal.

  The distributor 32 distributes the WDM signal propagated through the optical fiber transmission line 51 to the optical communication apparatuses 21 to 2N. As the distributor 32, a 1 × N star coupler or WSS can be used. The distributed WDM signal is input to the optical communication apparatuses 21 to 2N.

  The optical communication devices 21 to 2N include optical receivers 201 to 20N. The optical receivers 201 to 20N receive an optical signal having a desired wavelength from the input WDM signal, convert it into an electrical signal, and output it as an output signal to the optical communication apparatuses 21 to 2N. The optical communication devices 21 to 2N perform processing such as multiplexing or demultiplexing on the output signals output from the optical receivers 201 to 20N, and output the processed signals to other communication devices. The optical receivers 201 to 20N may be disposed outside the optical communication devices 21 to 2N. Alternatively, as illustrated in FIG. 1, the optical receivers 201 to 20N may be provided inside the optical communication devices 21 to 2N. The optical communication device 21 including the optical receiver 201 can be referred to as an optical reception device.

  FIG. 2 is a diagram illustrating a configuration example of the optical receiver 201 provided in the optical communication device 21. Since the optical receivers 201 to 20N have the same configuration, the optical receiver 201 will be described below as an example. The optical receiver 201 includes a local oscillation light source (Local Oscillator, LO) 251, a coherent receiver 252, a light receiving unit 253, and a signal processing unit 254.

  The local oscillation light source 251 serves as local oscillation means for outputting light of a predetermined wavelength (LO light). The LO 251 is, for example, a laser light source, and a wavelength variable laser may be used. The coherent receiver 252 serves as coherent receiving means for selectively coherently receiving an optical signal having a desired wavelength by causing the WDM signal input from the distributor 32 of FIG. 1 to interfere with the LO light.

  The light receiving unit 253 converts the optical signal received by the coherent receiver 252 into an electrical signal. The electric signal output from the light receiving unit 253 is hereinafter referred to as a reception signal. The light receiving unit 253 may include a photodiode. The light receiving unit 253 serves as a light receiving unit that converts an optical signal selectively received by the coherent receiver 252 into a reception signal that is an electrical signal.

  The signal processing unit 254 electrically processes the electrical signal output from the light receiving unit 253. The signal processing unit 254 performs signal quality compensation processing such as current-voltage conversion, analog-digital conversion, amplification and decoding, and dispersion compensation, for example. Some or all of the functions of the signal processing unit 254 may be mounted on an integrated circuit (IC), and these functions may be controlled from the outside.

  The signal processing unit 254 has a function of changing the reception band of the reception signal according to the characteristics of the optical signal having a desired wavelength to be received. The characteristics of the optical signal include, but are not limited to, a wavelength, a symbol rate, a bit rate, and a modulation method. That is, the signal processing unit 254 serves as signal processing means for processing the received signal in a reception band corresponding to the characteristics of the optical signal selectively received by the coherent receiver 252.

  FIG. 3 is a sequence diagram illustrating an operation example of the optical receiver 201. The LO 251 oscillates LO light having a wavelength corresponding to the channel to be received among the wavelengths (channels) of the optical signal included in the WDM signal and outputs the LO light to the coherent receiver 252 (step S01 in FIG. 3). The coherent receiver 252 generates interference light by causing the received light (WDM signal) to interfere with the LO light (step S02). The light receiving unit 253 converts the interference light output from the coherent receiver 252 into a reception signal that is an electrical signal (step S03). In this way, the optical signal of the channel corresponding to the wavelength of the LO light is selectively received from the WDM signal. The signal processing unit 254 electrically processes the reception signal input from the light receiving unit 253 in a band corresponding to the characteristics of the received signal light (step S04).

  Here, the reception band in the signal processing unit 254 will be described. FIG. 4 is a diagram illustrating an example of the relationship between the channel interval of the WDM signal and the reception band in the present embodiment. As described with reference to FIGS. 14 and 15, when the width of the WDM channel slot becomes narrow, crosstalk occurs when the reception band of the signal processing unit 254 remains wide (BW1). In the present embodiment, the signal processing unit 254 narrows the reception band 824 to include only the spectrum of the desired channel (BW2). As a result, crosstalk due to the spectrum of the adjacent channel is reduced, and the quality of the received signal is improved. In other words, the signal processing unit 254 changes the reception band so that only a desired optical signal is received according to the symbol rate and modulation method of the received signal, so that the quality of the received signal resulting from the change of the symbol rate and modulation method. Reduction can be suppressed.

  As described above, the optical receiver 201 of the present embodiment can provide an optical receiver that can flexibly cope with changes in received signal characteristics such as a symbol rate and a modulation method while ensuring the quality of the received signal.

(Second Embodiment)
FIG. 5 is a diagram illustrating a configuration example of an optical receiver 201A according to the second embodiment of the present invention. The optical receiver 201A is different from the optical receiver 201 of the first embodiment in that it includes a control unit 255 and an interface 256. Other than that, the configuration of the optical receiver 201A is the same as that of the optical receiver 201, and redundant description is omitted. The optical receiver 201 </ b> A is connected to the optical communication device 21. The optical receiver 201A may be included in the optical communication device 21 as shown in FIG.

  The interface 256 is an electrical interface for connecting the optical receiver 201A to the optical communication device 21 that is a host. The interface 256 is an electrical connector, for example. The control unit 255 receives a control signal from the optical communication device 21 via the interface 256. The control signal is a signal that instructs the optical receiver 201A to switch the characteristics of the received optical signal. The control signal is, for example, an instruction for changing the symbol rate of the optical signal, changing the bit rate, changing the modulation method, or the like.

  The control unit 255 generates setting information for controlling the reception band of the signal processing unit 254 according to the control signal notified from the optical communication device 21 and notifies the signal processing unit 254 of the setting information. The control signal may directly instruct the signal processing unit 254 to change the reception band. Alternatively, the control unit 255 may generate setting information including the reception band based on a table in which the relationship between the content of the control signal and the reception band is described. That is, the control unit 255 receives a control signal from the optical communication device 21 via the interface 256, generates setting information for changing the reception band of the signal processing unit 254 based on the control signal, and generates the setting information. It serves as a control means for notifying H.254.

  FIG. 6 is an example of a table for setting the reception band by the control signal. For example, when the control unit 255 receives a control signal “switch to wavelength 1” from the optical communication device 21, the control unit 255 refers to the table of FIG. 6 and notifies the signal processing unit 254 of setting information whose reception band is BW1. . The signal processing unit 254 sets the reception band to BW1 according to the notified setting information. FIG. 6 illustrates symbol signal switching, bit rate switching, and modulation system switching in addition to wavelength switching as the contents of the control signal. When receiving the control signal including these switching instructions, the control unit 255 refers to the table of FIG. 6, generates corresponding reception band setting information, and notifies the signal processing unit 254 of the setting information. The signal processing unit 254 processes a reception signal within the reception band set based on the setting information.

  The table in FIG. 6 is stored as data in the control unit 255. BW1 to BW8 in FIG. 6 indicate specific numerical values of frequency bandwidths in which the signal processing unit 254 processes received signals. BW1 to BW8 need not all be different, and the same band may be included.

  FIG. 7 is a sequence diagram illustrating an operation example of the optical receiver 201A. The optical communication device 21 generates a control signal and notifies the control unit 255 via the interface 256 (step S11 in FIG. 7). When receiving the control signal, the control unit 255 refers to the table of FIG. 6 and generates setting information (for example, setting the reception band to BW1) corresponding to the instruction (for example, switching to the wavelength 1) included in the control signal. The signal processor 254 is notified (step S12). When receiving the setting information, the signal processing unit 254 sets the reception band for processing the received signal to the reception band indicated by the setting information. Then, the signal processing unit 254 processes the reception signal output from the light receiving unit 253 within the reception band and outputs the processed signal to the optical communication device 21 as an output signal (step S13).

  The processing performed by the control unit 255 may be realized by a computer control program using computer hardware included in the control unit 255. Further, a digital signal processor (DSP) may be used for the signal processing unit 254, and the signal processing unit 254 may have the function of the control unit 255. The control program may be stored in a storage device (for example, a semiconductor memory) included in the control unit 255.

  The optical receiver 201 </ b> A of the second embodiment having such a configuration sets the band of the received signal in the signal processing unit 254 based on the control signal received from the optical communication device 21. As a result, it is possible to provide an optical receiver that can flexibly cope with a change in the characteristics of the received signal while ensuring the quality of the received signal. Furthermore, the optical receiver 201 </ b> A can set the reception band of the signal processing unit 254 from the outside according to the change in the characteristics of the reception signal.

(Third embodiment)
FIG. 8 is a diagram illustrating a configuration example of an optical receiver 201B according to the third embodiment of the present invention. Compared with the optical receiver 201 of the second embodiment, the optical receiver 201B has a function in which the control unit 255 generates setting information based on the quality information notified from the signal processing unit 254, and the control unit 255 The difference is that a function of controlling the LO 251 is provided. Other than that, the configuration of the optical receiver 201B is the same as that of the optical receiver 201A, and redundant description is omitted. The optical receiver 201B may be included in the optical communication device 21 as illustrated in FIG.

  The signal processing unit 254 monitors the received signal and notifies the control unit 255 of information (quality information) related to the quality of the received signal. The quality information to be monitored is, for example, at least one of the error rate and the amplitude of the received signal, but is not limited thereto. The control unit 255 controls the reception band of the signal processing unit 254 according to the quality information notified from the signal processing unit 254. The reception band setting based on the quality information may be performed with priority over the reception band setting based on the control signal notified from the optical communication device 21.

  FIG. 9 is a sequence diagram illustrating an operation example of the optical receiver 201B. The optical communication device 21 generates a control signal and notifies the control unit 255 (step S21 in FIG. 9). When the control unit 255 receives the control signal, the control unit 255 generates setting information (for example, the reception band is set to BW1) corresponding to the instruction (for example, switching to the wavelength 1) included in the control signal, and transmits the setting information to the signal processing unit 254. Notification is made (step S22). Here, the control unit 255 may refer to the table of FIG. When receiving the setting information, the signal processing unit 254 sets the band for processing the received signal to the reception band indicated by the setting information. Then, the signal processing unit 254 processes the reception signal output from the light receiving unit 253 within the reception band, and outputs it as an output signal to the optical communication device 21 (step S23).

  The signal processing unit 254 notifies the control unit 255 of the quality information of the received signal processed in step S23. The control unit 255 generates setting information based on the quality information notified from the signal processing unit 254, and notifies the signal processing unit 254 (step S24). The setting information generated in step S24 is a reception band set in the signal processing unit 254. For example, the setting information may be any one of BW1 to BW8 shown in the right column of FIG. 6, or may be a value different from BW1 to BW8. Good. The signal processing unit 254 sets the reception band to the band set based on the quality information in step S24. Then, the signal processing unit 254 processes the reception signal output from the light receiving unit 253 within the reception band, and outputs it as an output signal to the optical communication device 21 (step S25).

  FIG. 10 is a diagram illustrating an example of setting a reception band based on quality information. In step S24, the control unit 255 generates setting information so that the quality indicated by the quality information notified from the signal processing unit 254 is improved. That is, the reception band indicated by the setting information generated in step S24 is dynamically controlled so that the quality of the received signal is high. Referring to FIG. 10, when the reception band (horizontal axis) of the signal processing unit 254 becomes wider than the optimum bandwidth, the received signal quality (vertical axis) decreases due to crosstalk with adjacent channels as described in FIG. To do. On the other hand, when the reception band becomes narrower than the optimum bandwidth, the spectrum of the reception signal processed within the reception band is deleted, so that the quality of the reception signal is lowered. For this reason, the control unit 255 notifies the signal processing unit 254 with setting information so that the reception band value is set to the reception band at which the received signal quality is peaked, which is indicated by the optimum bandwidth in FIG. Bandwidth may be controlled dynamically. For example, when the error rate of the received signal is used as the quality information, the control unit 255 controls to increase or decrease the reception band notified to the signal processing unit 254 so that the error rate decreases. Also good. By such control, the reception band approaches the optimum bandwidth shown in FIG.

  The control unit 255 may notify the LO 251 of setting information for setting the wavelength of the LO light and the light output. The LO 251 may change the wavelength and amplitude of the LO light based on the setting information notified from the control unit 255. The control unit 255 can cope with a change in the wavelength of the received signal by providing a function for setting the LO light. In step S24, the control unit 255 may notify the LO 251 of setting information regarding the wavelength of the LO light or the optical output so that the quality indicated by the quality information is improved.

  The optical receiver 201 </ b> B of the third embodiment having such a configuration sets the band of the received signal in the signal processing unit 254 based on the control signal received from the optical communication device 21. As a result, it is possible to provide an optical receiver that can flexibly cope with a change in the characteristics of the received signal while ensuring the quality of the received signal. Further, the optical receiver 201B can set the reception band of the signal processing unit 254 from the outside according to the change in the characteristics of the reception signal.

  Furthermore, since the control unit 255 sets the reception band of the signal processing unit 254 based on the quality information, the optical receiver 201B can autonomously set the reception band so that the quality of the received signal is better.

(Fourth embodiment)
FIG. 11 is a diagram illustrating a configuration example of an optical transceiver 201C according to the fourth embodiment of this invention. The configuration and operation of the optical transceiver 201C other than those described below are the same as those of the optical receivers 201A and 201B, and redundant description will be omitted.

  The optical transceiver 201C is configured by further adding an optical branching unit 257 and an optical modulator 258 to the optical receivers 201A and 201B. The optical branching unit 257 distributes the LO light output from the LO 251 to the coherent receiver 252 and the optical modulator 258. As the optical branching unit 257, a 1 × 2 optical coupler may be used. The optical branching unit 257 serves as an optical branching unit that branches the LO light and outputs the LO light to the coherent receiver 252 and the optical modulator 258.

  The optical modulator 258 modulates the LO light distributed from the optical branching unit 257 with the transmission signal received from the optical communication device 21 and outputs the modulated light as transmission light. The optical modulator 258 is, for example, an optical waveguide modulator made of silicon. The optical modulator 258 serves as an optical modulation unit that generates transmission light obtained by modulating the branched LO light using a transmission signal received from the optical communication device 21 via the interface 256.

  The control unit 255 receives a control signal and a transmission signal from the optical communication device 21 via the interface 256. The control unit 255 generates setting information for the signal processing unit 254, the LO 251 and the optical modulator 258 based on the control signal, and notifies the generated setting information to each. The control unit 255 may have a function of setting the reception band of the signal processing unit 254 based on the received signal quality information described in the third embodiment. The optical transceiver 201C may be included in the optical communication devices 21 to 2N. The optical transceiver 201C may be provided in the optical communication devices 11 to 1N21. The optical communication devices 11 to 1N and 21 to 2N each including the optical transceiver 201C can be called optical transmission / reception devices.

  FIG. 12 is a table showing an example of setting contents in each part of the optical transceiver 201C by the control signal. The control signal received by the control unit 255 from the optical communication device 21 includes, for example, an instruction to switch optical signal characteristics such as wavelength (channel) switching, bit rate switching, symbol rate switching, modulation method switching, and the like.

  When the wavelength switching is included in the control signal, the control unit 255 generates setting information for setting the TIA voltage amplitude, the ADC dynamic range, the dispersion, and the skew compensation value of the signal processing unit 254 and notifies the signal processing unit 254 of the setting information. To do. TIA is a Trans Impedance Amplifier, and ADC is an Analog to Digital Converter. These are included in the signal processing unit 254. The TIA converts the output of the light receiving unit 253 into a current voltage. The ADC converts the TIA output into a digital signal.

  The control unit 255 notifies the optical modulator 258 of the setting information of the bias voltage and the driving voltage corresponding to the switched wavelength, and notifies the LO 251 of the setting information of the wavelength and the optical output corresponding to the switched wavelength. By setting the wavelength of the LO 251 by the setting information, the transmission wavelength and the reception wavelength of the optical transceiver 201C can be changed simultaneously. Further, when the control signal includes wavelength switching and the bandwidth of the received signal at the switched wavelength is different, the control unit 255 changes the bandwidth of the received signal to the signal processing unit 254. Notify the setting information.

  When the control signal includes a bit rate, symbol rate, or modulation mode switching instruction, the control unit 255 changes the setting of the optical output of the LO 251 in addition to the bandwidth of the received signal. Further, the control unit 255 changes the settings of the bias voltage and drive voltage of the optical modulator 258 and the settings of the TIA voltage amplitude, ADC dynamic range, dispersion, and skew compensation value of the signal processing unit 254.

  Note that the setting items in FIG. 12 are examples, and the switching content and the setting content in each unit included in the control signal are not limited to the description in FIG. The control unit 255 may have a table of the format shown in FIG. 6 for each setting content, and may generate setting information corresponding to the content of the control signal with reference to the table.

  FIG. 13 is a sequence diagram illustrating an operation example of the optical transceiver 201C. The optical communication device 21 generates a control signal and notifies the control unit 255 (step S31 in FIG. 12). When receiving the control signal, the control unit 255 generates setting information corresponding to the instruction included in the control signal, and notifies the signal processing unit 254, the LO 251 and the optical modulator 258 (step S32). An example of the setting information corresponding to the control signal has been described with reference to FIG.

  When the LO 251 receives the setting information, the LO 251 generates LO light in which the wavelength and the optical output are set based on the contents (step S33). The coherent receiver 252 and the light receiving unit 253 perform coherent detection on the received light using the LO light, and output the received signal to the signal processing unit 254 (step S34).

  The signal processing unit 254 sets the reception band, TIA voltage amplitude, ADC dynamic range, dispersion, and skew compensation value of the received signal based on the notified setting information. Then, the signal processing unit 254 processes the received signal under the set conditions and outputs it as an output signal to the optical communication device 21 (step S35). Here, the signal processing unit 254 may notify the control unit 255 of the quality information of the received signal processed in step S35. In this case, the control unit 255 generates setting information based on the quality information notified from the signal processing unit 254, and notifies the signal processing unit 254 (step S36). Then, the signal processing unit 254 processes the received signal based on the notified setting information (step S37). When the process of step S36 is not performed, in step S37, the signal processing unit 254 continues the process of the received signal based on the setting information generated in step S32.

  When notified of the setting information generated in step S32, the optical modulator 258 sets the bias voltage and the driving voltage based on the contents. Then, the optical modulator 258 modulates LO light using the transmission signal output from the optical communication device 21 and outputs transmission light (step S38).

  As described above, the optical transceiver 201C of the fourth embodiment has functions similar to those of the optical receivers 201A and 201B regarding processing of received signals, and also has a function of transmitting optical signals. For this reason, a bidirectional optical communication system can be constructed by arranging optical communication devices (optical transmission / reception devices) including the optical transceiver 201C so as to face each other. In FIG. 1, the optical transceiver 201C is mounted on the optical communication devices 11 to 1N and 21 to 2N, and a transmission path is also installed in the direction from the optical communication devices 21 to 2N to the optical communication devices 11 to 1N. An optical communication system capable of bidirectional transmission of signals can be constructed.

  As mentioned above, although this invention was demonstrated with reference to embodiment, this invention is not limited to said embodiment. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

  Further, the configurations described in the respective embodiments are not necessarily mutually exclusive. The operation and effect of the present invention may be realized by a configuration in which all or part of the above-described embodiments are combined.

DESCRIPTION OF SYMBOLS 1 Optical communication system 21 Optical communication apparatus 31 Coupler 32 Divider 41, 42 Optical amplifier 51 Optical fiber transmission line 201, 201A, 201B Optical receiver 201C Optical transceiver 251 Local oscillation light source 252 Coherent receiver 253 Light receiving part 254 Signal processing part 255 Control unit 256 Interface 257 Optical branching unit 258 Optical modulator 821-823 Optical signal 824 Reception band 831-833 Optical signal

Claims (18)

Local oscillation means for outputting local oscillation light of a predetermined wavelength;
Coherent receiving means for selectively receiving the optical signal of the predetermined wavelength from the wavelength multiplexed optical signal by causing the wavelength multiplexed optical signal to interfere with the local oscillation light;
A light receiving means for converting the optical signal selectively received by the coherent receiving means into an electrical signal;
Signal processing means for processing the electrical signal and outputting it as an output signal in a reception band according to the characteristics of the optical signal selectively received by the coherent receiving means;
An optical receiver comprising:   The optical receiver according to claim 1, wherein the characteristic of the optical signal includes any one of a symbol rate, a bit rate, and a modulation method of the optical signal. An electrical interface with other devices,
Receiving a control signal instructing switching of the characteristics of the optical signal from the other device via the interface, generating setting information for controlling a reception band of the signal processing means based on the control signal, and setting the setting Control means for notifying the signal processing means of information;
The optical receiver according to claim 1, further comprising: The signal processing means notifies the control means of quality information of the electrical signal;
The control means controls a reception band of the signal processing means based on the quality information.
The optical receiver according to claim 3. The control means controls the reception band of the signal processing means so that the quality information becomes better.
The optical receiver according to claim 4. The optical receiver according to claim 4, wherein the quality information includes at least one of an error rate and an amplitude of the electrical signal. An optical receiver according to any one of claims 3 to 6,
Optical branching means for branching the locally oscillated light and outputting it to the coherent receiving means and the light modulating means;
Using the transmission signal received from the other device via the interface, modulating the local oscillation light output by the optical branching means, and outputting the modulated light as transmission light;
Is an optical transceiver further comprising:
The control means generates the setting information for controlling the signal processing means, the local oscillation means, and the optical modulation means based on the control signal, and the setting information is used as the signal processing means, the local oscillation means, and the Notify the light modulation means,
Optical transceiver.   An optical receiver comprising the optical receiver according to claim 3.   An optical transceiver comprising the optical transceiver according to claim 7, processing the output signal output from the optical transceiver, and outputting the transmission signal to the optical transceiver.   An optical communication system in which the optical transmission / reception devices according to claim 9 are connected so as to be able to communicate with each other. Outputs local oscillation light of a predetermined wavelength,
Selectively receiving the optical signal of the predetermined wavelength from the wavelength multiplexed optical signal by causing the wavelength multiplexed optical signal to interfere with the local oscillation light;
Selectively converting the received optical signal into an electrical signal;
Processing the electrical signal in a reception band according to the characteristics of the optical signal selectively received;
Optical reception method.   The optical reception method according to claim 11, wherein the characteristic of the optical signal includes any one of a symbol rate, a bit rate, and a modulation method of the optical signal. Receiving a control signal instructing switching of the characteristics of the optical signal from the other device via an electrical interface with the other device;
Generating setting information for controlling the reception band based on the control signal;
The optical receiving method according to claim 11 or 12. Controlling the reception band based on information on the quality of the electrical signal;
The optical receiving method according to claim 13. Controlling the reception band so that the quality information is better;
The optical receiving method according to claim 14.   The optical reception method according to claim 14 or 15, wherein the quality information includes at least one of an error rate and an amplitude of the electrical signal. Branching the local oscillation light output from the local oscillation means,
One of the local oscillation light branched by the received transmission signal is output by the optical modulation means to output the transmission light,
Information for controlling the reception band, the local oscillating means, and the optical modulation means is included in the setting information based on the control signal, and generated.
The optical receiving method according to claim 13. Local oscillation means for outputting local oscillation light of a predetermined wavelength, and coherent reception for selectively receiving the optical signal of the predetermined wavelength from the wavelength multiplexed optical signal by causing a wavelength multiplexed optical signal to interfere with the local oscillation light Means, a light receiving means for converting the optical signal selectively received by the coherent receiving means into an electric signal, and a reception band corresponding to the characteristics of the optical signal selectively received by the coherent receiving means. A computer of an optical receiver comprising signal processing means for processing a signal and an electrical interface with another device;
Receiving a control signal instructing switching of the characteristics of the optical signal from the other device via the interface;
A procedure for generating setting information for controlling the reception band of the signal processing means based on the control signal;
A procedure for notifying the signal processing means of the setting information;
An optical receiver control program for executing

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