Optical communication system and optical communication device

Abstract

To provide an optical communication device and an optical communication system that suppress deterioration in the quality of received signals when a transponder has a plurality of optical transmitters and a plurality of optical receivers.SOLUTION: In an optical communication system, a signal processing unit of an optical communication device detects a first combination of the roll-off rate of an RRC filter of an optical transmitter 113 and the center frequency of a light source and a second combination of the roll-off rate of an RRC filter of an optical transmitter 114 and the center frequency of a light source of the optical transmitter 114 when the total value of BER1 and BER2 is minimized; sets the center frequency of the light source based on the first combination; sets the roll-off rate of the first RRC filter based on the first combination; sets the center frequency of the light source of the optical transmitter 114 based on the second combination; and sets the roll-off rate of the second RRC filter based on the second combination. This allows the BER of data received by other optical communication devices to be kept low.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to an optical communication system , and optical communication device Regarding. [Background technology]

[0002] In recent years, the increasing demand for communications has created a demand for optical communication technologies that can achieve high-density, high-capacity communications. Simply increasing the number of wavelengths multiplexed and expanding optical fiber networks is insufficient to meet the growing demand. Therefore, it is necessary to improve the communication speed per wavelength or the communication speed in multi-carrier communications from 100 Gbps to 400 Gbps or 800 Gbps. However, as communication speeds increase, degradation of received signal quality, such as distortion of optical signal waveforms due to chromatic dispersion and polarization mode dispersion in optical fibers, becomes more serious.

[0003] Here, a technique for reducing the filter penalty, which is a degradation in the quality of a received signal, has been proposed (see Patent Document 1). The optical transmission system of Patent Document 1 includes a transponder unit having one transmitting unit and one receiving unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-213062 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, a transponder as shown in Fig. 15 has been proposed. The transponder 900 in Fig. 15 has an IF (Interface) unit 901, a signal processing unit 902, optical transmitters 903_1, 903_2, ..., 903_n (n is a positive integer), and optical receivers 904_1, 904_2, ..., 904_n (n is a positive integer). In this way, the transponder 900 has a plurality of optical transmitters and a plurality of optical receivers.

[0006] Even when a transponder has multiple optical transmitters and multiple optical receivers, such as transponder 900, degradation of the quality of the received signal becomes a problem. The above technology is proposed for a case where the transponder has one transmitter and one receiver. The above technology cannot be simply applied to a case where the transponder has multiple optical transmitters and multiple optical receivers. Therefore, degradation of the quality of the received signal becomes a problem when the transponder has multiple optical transmitters and multiple optical receivers.

[0007] An object of the present disclosure is to suppress deterioration in the quality of received signals when a transponder has multiple optical transmitters and multiple optical receivers. [Means for solving the problem]

[0008] According to one aspect of the present disclosure, there is provided an optical communication system including: a transponder including a first optical transmitter having a first light source, a second optical transmitter having a second light source, and a plurality of optical receivers; a first optical communication device having a signal processing unit that functions as a first low-pass filter for an electrical signal input to the first optical transmitter and a second low-pass filter for an electrical signal input to the second optical transmitter; and a second optical communication device that calculates a first bit error rate of data based on the optical signal transmitted by the first optical transmitter and a second bit error rate of data based on the optical signal transmitted by the second optical transmitter. The signal processing unit detects a first combination, which is a combination of the roll-off rate of the first low-pass filter and the center frequency of the first light source, when the sum of the first bit error rate and the second bit error rate is minimum, and a second combination, which is a combination of the roll-off rate of the second low-pass filter and the center frequency of the second light source, and sets the center frequency of the first light source in the first optical transmitter based on the first combination, sets the roll-off rate of the first low-pass filter in the first low-pass filter based on the first combination, sets the center frequency of the second light source in the second optical transmitter based on the second combination, and sets the roll-off rate of the second low-pass filter in the second low-pass filter based on the second combination. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to suppress deterioration in the quality of received signals when a transponder has multiple optical transmitters and multiple optical receivers. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating an optical communication system according to a first embodiment. [Figure 2] 1 is a diagram illustrating hardware included in an optical communication device according to a first embodiment. [Figure 3] 1 is a block diagram showing functions of an optical communication device according to a first embodiment. [Figure 4]2 is a block diagram showing the functions of the optical transmitter according to the first embodiment; FIG. [Figure 5] 1 is a block diagram showing functions of an optical communication device according to a first embodiment. [Figure 6] 4 is a flowchart illustrating an example of processing executed by the optical communication device according to the first embodiment. [Figure 7] FIG. 4 is a diagram illustrating the relationship between the roll-off rate of the RRC filter and the transmission optical spectrum bandwidth according to the first embodiment. [Figure 8] 10A and 10B are diagrams showing a specific example for explaining the effect of the first embodiment. [Figure 9] FIG. 10 is a diagram illustrating an example in which the transponder of the first embodiment has three or more optical transmitters. [Figure 10] FIG. 10 is a diagram illustrating an optical communication system according to a second embodiment. [Figure 11] FIG. 10 is a block diagram showing the functions of an optical communication device according to a second embodiment. [Figure 12] FIG. 10 is a block diagram showing the functions of an optical communication device according to a second embodiment. [Figure 13] 10 is a flowchart illustrating an example of processing executed by the optical communication device according to the second embodiment. [Figure 14] FIG. 10 is a diagram illustrating an example of a frame format according to the second embodiment. [Figure 15] FIG. 10 is a diagram illustrating an example in which a transponder has multiple optical transmitters and multiple optical receivers. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments will be described with reference to the drawings. The following embodiments are merely examples, and various modifications are possible within the scope of the present disclosure.

[0012] Embodiment 1 1 is a diagram illustrating an optical communication system according to a first embodiment. The optical communication system includes an optical communication device 100 and an optical communication device 200. The optical communication system may include a control device 300. The optical communication system may be a multi-carrier optical communication system or a dual-carrier optical communication system.

[0013] The optical communication device 100 and the optical communication device 200 communicate with each other via optical fibers. The control device 300 communicates with the optical communication device 100 and the optical communication device 200. For example, the control device 300 communicates with the optical communication device 100 and the optical communication device 200 using an OSC (Optical Supervisory Channel).

[0014] Furthermore, the optical communication device 100 communicates with one or more client devices. Furthermore, the optical communication device 200 communicates with one or more client devices. Note that client devices communicating with the optical communication device 100 and the optical communication device 200 are not shown in the drawings. A client signal is transmitted and received between the optical communication device 100 and the client device. A client signal is transmitted and received between the optical communication device 200 and the client device.

[0015] The control device 300 monitors the optical communication device 100 and the optical communication device 200. The function of the control device 300 will be described in detail later. 1 shows two optical communication devices. The optical communication system may include three or more optical communication devices. When the optical communication system includes three or more optical communication devices, the control device 300 monitors the three or more optical communication devices.

[0016] The optical communication device 100 is also referred to as a first optical communication device, and the optical communication device 200 is also referred to as a second optical communication device.

[0017] Next, the hardware of the optical communication device 100 will be described. 2 is a diagram showing hardware included in the optical communication device according to the embodiment 1. The optical communication device 100 includes a processor 101, a volatile storage device 102, and a non-volatile storage device 103.

[0018] The processor 101 controls the entire optical communication device 100. For example, the processor 101 is a central processing unit (CPU) or a field programmable gate array (FPGA). The processor 101 may be a multiprocessor. The optical communication device 100 may also include a processing circuit.

[0019] The volatile storage device 102 is a main storage device of the optical communication device 100. For example, the volatile storage device 102 is a random access memory (RAM). The nonvolatile storage device 103 is an auxiliary storage device of the optical communication device 100. For example, the nonvolatile storage device 103 is a hard disk drive (HDD) or a solid state drive (SSD). The optical communication device 200 and the control device 300 also include a processor, a volatile storage device, and a non-volatile storage device.

[0020] Next, the functions of the optical communication device 100 will be described. 3 is a block diagram showing the functions of the optical communication device of the first embodiment. The optical communication device 100 includes a transponder 110, an optical multiplexing / demultiplexing unit 120, an optical amplifying unit 130, and a control unit 140. The transponder 110 includes an IF unit 111, a signal processing unit 112, optical transmitters 113 and 114, and optical receivers 115 and 116. The IF unit 111 and the signal processing unit 112 may be located outside the transponder 110. 3 shows a case where the optical communication device 100 has one transponder, but the optical communication device 100 may have multiple transponders.

[0021] A part or all of the control unit 140 may be realized by a processing circuit. Also, a part or all of the control unit 140 may be realized as a module of a program executed by the processor 101. Furthermore, when the IF unit 111 and the signal processing unit 112 are located outside the transponder 110, a part or all of the IF unit 111 and the signal processing unit 112 may be realized as a module of a processing circuit or a program executed by the processor 101.

[0022] First, the transmission function of the optical communication device 100 will be described. The IF unit 111 receives a client signal from a client device. The IF unit 111 converts the client signal into a format for WDM (Wavelength Division Multiplexing). The converted client signal is input to the signal processing unit 112. The signal processing unit 112 executes digital filtering. For example, the signal processing unit 112 executes, as digital filtering, digital signal processing for shaping the waveform of an input signal using an RRC filter (Root Raised Cosine filter).

[0023] The RRC filter will now be described. The signal processing unit 112 has the function of a first RRC filter for the electrical signal input to the optical transmitter 113. The RRC filter is a type of low-pass filter. Therefore, the first RRC filter may also be called a first low-pass filter. The signal processing unit 112 is realized as a processing circuit or a program module executed by a processor. For example, the processor is a DSP (Digital Signal Processor). The signal processing unit 112 may also have a low-pass filter circuit instead of the first RRC filter. The signal processing unit 112 performs D (Digital) / A (Analog) conversion on the electrical signal processed by the first RRC filter, and transmits the converted signal to the optical transmitter 113.

[0024] The signal processing unit 112 also has a function as a second RRC filter for the electrical signal input to the optical transmitter 114. The second RRC filter may be called a second low-pass filter. The signal processing unit 112 may also have a low-pass filter circuit instead of the second RRC filter. The signal processing unit 112 performs D / A conversion on the electrical signal processed by the second RRC filter, and transmits the converted signal to the optical transmitter 114.

[0025] The optical transmitters 113 and 114 convert electrical signals into transmission optical signals and transmit the transmission optical signals to the optical multiplexing / demultiplexing unit 120. The optical transmitters will be described in detail. Here, the optical transmitters 113 and 114 have the same functions. Therefore, the functions of the optical transmitter 113 will be described. And the description of the functions of the optical transmitter 114 will be omitted.

[0026] 4 is a block diagram showing the functions of the optical transmitter according to the embodiment 1. The optical transmitter 113 includes a control unit 113a, a light source 113b, and a modulation unit 113c. A part or all of the control unit 113a and the modulation unit 113c may be realized by a processing circuit included in the optical transmitter 113. Also, a part or all of the control unit 113a and the modulation unit 113c may be realized as a program module executed by a processor included in the optical transmitter 113.

[0027] The control unit 113 a adjusts the voltage level of the electrical signal input to the optical transmitter 113 . The modulation section 113c generates a transmission optical signal 1 by superimposing the electrical signal, the voltage level of which has been adjusted, onto the light emitted by the light source 113b.

[0028] Returning to FIG. 3, the function of the optical multiplexing / demultiplexing unit 120 will be described. The optical multiplexing / demultiplexing unit 120 multiplexes the transmission optical signal 1 generated by the optical transmitter 113 and the transmission optical signal 2 generated by the optical transmitter 114. In this way, the optical signals are multiplexed. The optical amplifier 130 amplifies the multiplexed optical signal to a predetermined level, and the amplified optical signal is transmitted to the optical communication device 200.

[0029] Next, the receiving function of the optical communication device 100 will be described. The optical communication device 100 receives the received optical signal (more specifically, the multiplexed optical signal) transmitted by the optical communication device 200. The optical amplifier 130 amplifies the received optical signal to a predetermined level. The amplified optical signal is input to the optical multiplexer / demultiplexer 120. The optical multiplexing / demultiplexing unit 120 demultiplexes the amplified optical signal (more specifically, the multiplexed optical signal). As a result, the amplified optical signal is demultiplexed into received optical signal 1 and received optical signal 2. Received optical signal 1 is input to optical receiver 115. Received optical signal 2 is input to optical receiver 116.

[0030] The optical receiver 115 demodulates the received optical signal 1 and converts it into an electrical signal. The converted electrical signal is input to the signal processing unit 112. The optical receiver 116 demodulates the received optical signal 2 and converts it into an electrical signal. The converted electrical signal is input to the signal processing unit 112. The signal processing unit 112 calculates a bit error rate (BER) of the demodulated electrical signal. The signal processing unit 112 transmits the demodulated electrical signal as a client signal to the IF unit 111. The IF unit 111 transmits the client signal to the client device.

[0031] The control unit 140 monitors the transponder 110, the optical multiplexing / demultiplexing unit 120, and the optical amplifying unit 130. The control unit 140 can also execute setting processes for the transponder 110, the optical multiplexing / demultiplexing unit 120, and the optical amplifying unit 130.

[0032] 5 is a block diagram showing the functions of the optical communication device of the first embodiment. The optical communication device 200 has a transponder 210, an optical multiplexing / demultiplexing unit 220, an optical amplifying unit 230, and a control unit 240. The transponder 210 has an IF unit 211, a signal processing unit 212, optical transmitters 213 and 214, and optical receivers 215 and 216. The IF unit 211 and the signal processing unit 212 may be located outside the transponder 210. 5 shows a case where the optical communication device 200 has one transponder, but the optical communication device 200 may have multiple transponders.

[0033] The functions of the transponder 210, the optical multiplexing / demultiplexing unit 220, the optical amplifying unit 230, and the control unit 240 are the same as those of the transponder 110, the optical multiplexing / demultiplexing unit 120, the optical amplifying unit 130, and the control unit 140. Therefore, a description of the functions of the transponder 210, the optical multiplexing / demultiplexing unit 220, the optical amplifying unit 230, and the control unit 240 will be omitted. Furthermore, the functions of the IF unit 211, the signal processing unit 212, the optical transmitters 213 and 214, and the optical receivers 215 and 216 are the same as those of the IF unit 111, the signal processing unit 112, the optical transmitters 113 and 114, and the optical receivers 115 and 116. Therefore, a description of the functions of the IF unit 211, the signal processing unit 212, the optical transmitters 213 and 214, and the optical receivers 215 and 216 will be omitted.

[0034] Next, the processing executed by the optical communication device 100 will be described with reference to a flowchart. Fig. 6 is a flowchart showing an example of processing executed by the optical communication device according to the first embodiment. Here, the center frequency of the light source 113b of the optical transmitter 113 at the start of Fig. 6 is assumed to be 188.4125 THz. Also, the center frequency of the light source of the optical transmitter 114 at the start of Fig. 6 is assumed to be 188.4875 THz.

[0035] Here, the optical transmitter 113 is also referred to as a first optical transmitter. The light source 113b is also referred to as a first light source. The optical transmitter 114 is also referred to as a second optical transmitter. The light source of the optical transmitter 114 is also referred to as a second light source.

[0036] (Step S11) The signal processing unit 112 sets the roll-off factor α of the first RRC filter to the minimum value of “0.” Here, the relationship between the roll-off factor α of the RRC filter and the transmission optical spectrum bandwidth is shown.

[0037] Fig. 7 is a diagram illustrating the relationship between the roll-off rate of the RRC filter and the transmission optical spectrum bandwidth according to the first embodiment. The vertical axis of the graph in Fig. 7 represents power, and the horizontal axis of the graph in Fig. 7 represents frequency. 7 shows the state of the transmission optical spectrum bandwidth when the roll-off rate α is set to “0”, “0.5”, or “1”. When the roll-off rate α is set to “0”, the transmission optical spectrum bandwidth is narrowed as much as possible. As described above, the signal processing unit 112 sets the roll-off factor α of the first RRC filter to the minimum value, 0. This narrows the transmission optical spectrum bandwidth of the optical signal transmitted by the optical transmitter 113 as much as possible.

[0038] Furthermore, the signal processing unit 112 sets the roll-off rate of the second RRC filter to the minimum value of “0.” This narrows the transmission optical spectrum bandwidth of the optical signal transmitted by the optical transmitter 114 as much as possible.

[0039] The optical transmitter 113 generates a transmission optical signal 1 when the roll-off factor α of the first RRC filter is set to "0". The optical transmitter 114 generates a transmission optical signal 2 when the roll-off factor α of the second RRC filter is set to "0". The optical multiplexing / demultiplexing unit 120 multiplexes the transmission optical signal 1 and the transmission optical signal 2. The optical amplifying unit 130 amplifies the multiplexed optical signal. The optical communication device 100 transmits the amplified optical signal to the optical communication device 200.

[0040] The optical communication device 200 receives the optical signal transmitted by the optical communication device 100. The optical amplifier 230 amplifies the optical signal. The optical multiplexer / demultiplexer 220 demultiplexes the amplified optical signal. As a result, the amplified optical signal is demultiplexed into a received optical signal 11 and a received optical signal 12. The received optical signal 11 is input to the optical receiver 215. The received optical signal 12 is input to the optical receiver 216. The optical receiver 215 converts the received optical signal 11 into an electrical signal. The converted electrical signal is input to the signal processing unit 212. The optical receiver 216 also converts the received optical signal 12 into an electrical signal. The converted electrical signal is input to the signal processing unit 212. The signal processing unit 212 calculates the BER (hereinafter referred to as BER1) of the electrical signal output by the optical receiver 215. The BER is obtained by dividing the number of error-corrected bits in the received data (i.e., the electrical signal) by the total number of bits in the received data. The signal processing unit 212 calculates the BER (hereinafter referred to as BER2) of the electrical signal output by the optical receiver 216. Note that BER1 may be referred to as a first bit error rate of data based on the optical signal transmitted by the optical transmitter 113. BER2 may be referred to as a second bit error rate of data based on the optical signal transmitted by the optical transmitter 114. The control unit 240 acquires BER1 and BER2. The control unit 240 transmits BER1 and BER2 to the control device 300.

[0041] The control device 300 receives BER1 and BER2 from the optical communication device 200. The control device 300 transmits BER1 and BER2 to the optical communication device 100.

[0042] The control unit 140 acquires BER1 and BER2. The control unit 140 transmits BER1 and BER2 to the signal processing unit 112. The signal processing unit 112 acquires BER1 and BER2. The signal processing unit 112 calculates the sum of BER1 and BER2.

[0043] (Step S12) When step S12 is executed after step S11, or when step S12 is executed after step S16, the signal processing unit 112 determines whether the sum of BER1 and BER2 is greater than a predetermined threshold. If the sum is greater than the threshold, the process proceeds to step S15. If the sum is equal to or less than the threshold, the process proceeds to step S13.

[0044] Furthermore, when step S12 is executed after step S14, the signal processing unit 112 determines whether the total value calculated in step S14 is greater than the previous total value (i.e., the total value calculated in step S14 executed immediately before this step S14, or the total value calculated in step S11 or step S16). If the total value calculated in step S14 is greater than the previous total value, the process proceeds to step S15. If the total value calculated in step S14 is equal to or less than the previous total value, the process proceeds to step S13.

[0045] (Step S13) The signal processing unit 112 narrows the interval between the center frequency of the light source 113b of the optical transmitter 113 and the center frequency of the light source of the optical transmitter 114 by a predetermined interval. For example, the signal processing unit 112 narrows the interval between the center frequency of the light source 113b of the optical transmitter 113 and the center frequency of the light source of the optical transmitter 114 by 5 GHz. This changes the center frequency of the light source 113b of the optical transmitter 113 and the center frequency of the light source of the optical transmitter 114.

[0046] The optical transmitter 113 generates a transmission optical signal 1 with the center frequency of the light source 113b changed. Similarly, the optical transmitter 114 generates a transmission optical signal 2 with the center frequency of the light source of the optical transmitter 114 changed. The optical multiplexing / demultiplexing unit 120 multiplexes the transmission optical signal 1 and the transmission optical signal 2. The optical amplifying unit 130 amplifies the multiplexed optical signal. The optical communication device 100 transmits the amplified optical signal to the optical communication device 200.

[0047] The optical communication device 200 receives the optical signal transmitted by the optical communication device 100. The optical amplifier 230 amplifies the optical signal. The optical multiplexer / demultiplexer 220 demultiplexes the amplified optical signal. As a result, the amplified optical signal is demultiplexed into a received optical signal 11 and a received optical signal 12. The received optical signal 11 is input to the optical receiver 215. The received optical signal 12 is input to the optical receiver 216. The optical receiver 215 converts the received optical signal 11 into an electrical signal. The converted electrical signal is input to the signal processing unit 212. The optical receiver 216 also converts the received optical signal 12 into an electrical signal. The converted electrical signal is input to the signal processing unit 212. The signal processing unit 212 calculates a BER1 of the electrical signal output by the optical receiver 215. The signal processing unit 212 calculates a BER2 of the electrical signal output by the optical receiver 216. The control unit 240 acquires the BER1 and BER2. The control unit 240 transmits BER1 and BER2 to the control device 300.

[0048] The control device 300 receives BER1 and BER2 from the optical communication device 200. The control device 300 transmits BER1 and BER2 to the optical communication device 100.

[0049] (Step S14) The signal processing unit 112 acquires BER1 and BER2 via the control unit 140. The signal processing unit 112 adds BER2 to BER1. As a result, the sum of BER1 and BER2 is calculated. Then, the process proceeds to step S12.

[0050] By repeating steps S12 to S14, the total value becomes minimum. That is, the signal processing unit 112 narrows the interval between the center frequency of the light source 113b of the optical transmitter 113 and the center frequency of the light source of the optical transmitter 114 until the total value becomes minimum. In this way, steps S12 to S14 are repeated until the interval between the center frequency of the light source 113b of the optical transmitter 113 and the center frequency of the light source of the optical transmitter 114 becomes optimal.

[0051] (Step S15) The signal processing unit 112 determines whether or not step S16 has been executed. If step S16 has not been executed, the process proceeds to step S16. If step S16 has been executed, the process proceeds to step S17.

[0052] (Step S16) The signal processing unit 112 sets the roll-off factor α of the first RRC filter to a value larger than the previous roll-off factor α. For example, the signal processing unit 112 sets the roll-off factor α to 0.1. The signal processing unit 112 also sets the center frequency of the light source 113b of the optical transmitter 113 to 188.4125 THz. That is, the signal processing unit 112 returns the center frequency of the light source 113b to its initial state.

[0053] The signal processing unit 112 sets the roll-off factor α of the second RRC filter to a value greater than the previous roll-off factor α. For example, the signal processing unit 112 sets the roll-off factor α to 0.1. The signal processing unit 112 also sets the center frequency of the light source of the optical transmitter 114 to 188.4875 THz. That is, the signal processing unit 112 returns the center frequency of the light source of the optical transmitter 114 to its initial state.

[0054] The optical transmitter 113 generates a transmission optical signal 1 when the roll-off factor α of the first RRC filter is changed. The optical transmitter 114 generates a transmission optical signal 2 when the roll-off factor α of the second RRC filter is changed. The optical multiplexing / demultiplexing unit 120 multiplexes the transmission optical signal 1 and the transmission optical signal 2. The optical amplifying unit 130 amplifies the multiplexed optical signal. The optical communication device 100 transmits the amplified optical signal to the optical communication device 200.

[0055] The optical communication device 200 receives the optical signal transmitted by the optical communication device 100. The optical amplifier 230 amplifies the optical signal. The optical multiplexer / demultiplexer 220 demultiplexes the amplified optical signal. As a result, the amplified optical signal is demultiplexed into a received optical signal 11 and a received optical signal 12. The received optical signal 11 is input to the optical receiver 215. The received optical signal 12 is input to the optical receiver 216. The optical receiver 215 converts the received optical signal 11 into an electrical signal. The converted electrical signal is input to the signal processing unit 212. The optical receiver 216 also converts the received optical signal 12 into an electrical signal. The converted electrical signal is input to the signal processing unit 212. The signal processing unit 212 calculates a BER1 of the electrical signal output by the optical receiver 215. The signal processing unit 212 calculates a BER2 of the electrical signal output by the optical receiver 216. The control unit 240 acquires the BER1 and BER2. The control unit 240 transmits BER1 and BER2 to the control device 300.

[0056] The control device 300 receives BER1 and BER2 from the optical communication device 200. The control device 300 transmits BER1 and BER2 to the optical communication device 100.

[0057] The control unit 140 acquires BER1 and BER2. The control unit 140 transmits BER1 and BER2 to the signal processing unit 112. The signal processing unit 112 acquires BER1 and BER2. The signal processing unit 112 calculates the sum of BER1 and BER2.

[0058] (Step S17) The signal processing unit 112 compares the total BER value that is the minimum value at the previous roll-off rate α (hereinafter referred to as the previous total BER value) with the total BER value that is the minimum value at the current roll-off rate α (hereinafter referred to as the current total BER value). The signal processing unit 112 determines whether or not the current total BER value is greater than the previous total BER value. If the current total BER value is greater than the previous total BER value, the process proceeds to step S18. If the current total BER value is equal to or less than the previous total BER value, the process proceeds to step S16.

[0059] (Step S18) The signal processing unit 112 sets the center frequency of the light source 113b of the optical transmitter 113 at the time of the previous total value of BER to the optical transmitter 113. The signal processing unit 112 sets the roll-off rate α at the time of the previous total value of BER to the first RRC filter. Furthermore, the signal processing unit 112 sets the center frequency of the light source of the optical transmitter 114 at the time of the previous total value of BER to the optical transmitter 114. The signal processing unit 112 sets the roll-off rate α at the time of the previous total value of BER to the second RRC filter.

[0060] In this way, signal processing unit 112 repeats steps S12 to S17 until the total BER value is minimized. That is, signal processing unit 112 repeats steps S12 to S17 until the optimum combination of roll-off rate and center frequency is detected.

[0061] According to the first embodiment, the signal processing unit 112 detects a combination (hereinafter referred to as a first combination) of the roll-off rate of the RRC filter of the optical transmitter 113 and the center frequency of the light source 113b, and a combination (hereinafter referred to as a second combination) of the roll-off rate of the RRC filter of the optical transmitter 114 and the center frequency of the light source of the optical transmitter 114, which minimizes the sum of BER1 and BER2. The signal processing unit 112 sets the center frequency of the light source 113b to the optical transmitter 113 based on the first combination. The signal processing unit 112 sets the roll-off rate of the first RRC filter to the first RRC filter based on the first combination. The signal processing unit 112 sets the center frequency of the light source of the optical transmitter 114 to the optical transmitter 114 based on the second combination. The signal processing unit 112 sets the roll-off rate of the second RRC filter to the second RRC filter based on the second combination. This allows the BER of data received by the optical communication device 200 to be kept low. Therefore, the optical communication system can suppress deterioration of the quality of the received signal when the transponder has a plurality of optical transmitters and a plurality of optical receivers.

[0062] Furthermore, the following may be realized by the processing of the optical communication device 100. The following will be explained with reference to the drawings. 8A and 8B are diagrams showing specific examples for explaining the effects of embodiment 1. The vertical axis of the graphs in Figs. 8A and 8B represents power, and the horizontal axis of the graphs in Figs. 8A and 8B represents frequency. Fig. 8(A) shows the state at the start of the processing in Fig. 6. Fig. 8(B) shows the state at the end of the processing in Fig. 6. As shown in FIG. 8, the optical communication device 100 can change the roll-off rate to narrow the bandwidth of each optical spectrum as much as possible and adjust the frequency spacing, thereby preventing the optical spectrum from narrowing due to exceeding the optical filter bandwidth of the optical multiplexing / demultiplexing unit 120.

[0063] Furthermore, the transponder 110 may have three or more optical transmitters, including the optical transmitter 113 and the optical transmitter 114, and three or more optical receivers. The transponder 210 may have three or more optical transmitters, including the optical transmitter 213 and the optical transmitter 214, and three or more optical receivers. When the transponder 110 and the transponder 210 have three or more optical receivers, the optical communication device 100 performs the following process. This process will be explained using the drawings.

[0064] Fig. 9 is a diagram illustrating an example in which the transponder according to the first embodiment has three or more optical transmitters. The vertical axis of the graph in Fig. 9 represents power, and the horizontal axis of the graph in Fig. 9 represents frequency.

[0065] Figure 9 shows the bandwidths of the optical transmitters. The center frequency of the bandwidth f1 is the smallest among the center frequencies of the light sources of the three or more optical transmitters. n The center frequency of is the greatest among the center frequencies of the light sources of the three or more optical transmitters. In the process of narrowing the frequency interval, the signal processing unit 112 determines the center frequency of the bandwidth f1 and the center frequency of the bandwidth f2. n Then, the signal processing unit 112 narrows the interval between the center frequency of the bandwidth f2 and the center frequency of the bandwidth f n-1 For example, the center frequency of the bandwidth f1 is considered to be the center frequency of the light source 113b of the optical transmitter 113, and the center frequency of the bandwidth fn The center frequency of the optical transmitter 114 may be considered to be the center frequency of the light source of the optical transmitter 114. In this case, the optical communication device 100 can obtain the same effect by performing the process of FIG.

[0066] Embodiment 2 Next, a description will be given of embodiment 2. In embodiment 2, differences from embodiment 1 will be mainly described. Furthermore, in embodiment 2, description of matters common to embodiment 1 will be omitted. 10 is a diagram showing an optical communication system according to the second embodiment. The optical communication system includes an optical communication device 100a and an optical communication device 200a.

[0067] Fig. 11 is a block diagram showing the functions of the optical communication device of the second embodiment. The components in Fig. 11 that are the same as those in Fig. 3 are assigned the same reference numerals as those in Fig. 3. The optical communication device 100a differs from the optical communication device 100 in that it does not have a control unit 140.

[0068] Fig. 12 is a block diagram showing the functions of the optical communication device of the second embodiment. The components in Fig. 12 that are the same as those in Fig. 5 are assigned the same reference numerals as those in Fig. 5. The optical communication device 200a differs from the optical communication device 200 in that it does not have a control unit 240.

[0069] Next, the process executed by the optical communication device 100a will be described with reference to a flowchart. Fig. 13 is a flowchart showing an example of processing executed by the optical communication device according to the second embodiment. Here, the center frequency of the light source 113b of the optical transmitter 113 at the start of Fig. 13 is assumed to be 188.4125 THz. Also, the center frequency of the light source of the optical transmitter 114 at the start of Fig. 13 is assumed to be 188.4875 THz.

[0070] (Step S21) The signal processing unit 112 sets the roll-off factor α of the first RRC filter to the minimum value of “0.” The signal processing unit 112 also sets the roll-off factor of the second RRC filter to the minimum value of “0.” The signal processing unit 112 also generates a frame including path information of the transmission source. An example of the frame format is shown below.

[0071] 14 is a diagram showing an example of a frame format according to the second embodiment. The signal processing unit 112 registers source path information in the overhead of the frame. In this way, the signal processing unit 112 generates a frame including the source path information.

[0072] The optical transmitter 113 converts a frame (i.e., an electrical signal) containing path information of the source into a transmission optical signal 1 when the roll-off rate α of the first RRC filter is set to "0". Similarly, the optical transmitter 114 converts a frame (i.e., an electrical signal) containing path information of the source into a transmission optical signal 2 when the roll-off rate α of the second RRC filter is set to "0". The optical multiplexing / demultiplexing unit 120 multiplexes the transmission optical signal 1 and the transmission optical signal 2. The optical amplifying unit 130 amplifies the multiplexed optical signal. The optical communication device 100a transmits the amplified optical signal to the optical communication device 200a.

[0073] The optical communication device 200a receives the optical signal transmitted by the optical communication device 100a. The optical amplifier 230 amplifies the optical signal. The optical multiplexer / demultiplexer 220 demultiplexes the amplified optical signal. As a result, the amplified optical signal is demultiplexed into a received optical signal 11 and a received optical signal 12. The received optical signal 11 is input to the optical receiver 215. The received optical signal 12 is input to the optical receiver 216. The optical receiver 215 converts the received optical signal 11 into an electrical signal. The converted electrical signal is input to the signal processing unit 212. The optical receiver 216 converts the received optical signal 12 into an electrical signal. The converted electrical signal is input to the signal processing unit 212. The signal processing unit 212 calculates a BER1 of the electrical signal output by the optical receiver 215. The signal processing unit 212 calculates a BER2 of the electrical signal output by the optical receiver 216.

[0074] The signal processing unit 212 generates a frame including BER1. Note that BER1 is registered in the overhead of the frame, as shown in FIG. 14. Similarly, the signal processing unit 212 generates a frame including BER2. The optical transmitter 213 converts the frame including BER1 (i.e., an electrical signal) into a transmission optical signal 11. Similarly, the optical transmitter 214 converts the frame including BER2 (i.e., an electrical signal) into a transmission optical signal 12. The optical multiplexing / demultiplexing unit 220 controls the optical switch that the optical multiplexing / demultiplexing unit 220 has, using the path information. The optical multiplexing / demultiplexing unit 220 multiplexes the transmission optical signal 11 and the transmission optical signal 12. The optical amplifier 230 amplifies the multiplexed optical signal. The optical communication device 200a transmits the amplified optical signal to the optical communication device 100a.

[0075] The signal processing unit 112 acquires the BER1 and BER2 via the optical receivers 115 and 116. The signal processing unit 112 calculates the sum of the BER1 and BER2.

[0076] (Step S22) When step S22 is executed after step S21, or when step S22 is executed after step S26, the signal processing unit 112 determines whether the sum of BER1 and BER2 is greater than a predetermined threshold. If the sum is greater than the threshold, the process proceeds to step S25. If the sum is equal to or less than the threshold, the process proceeds to step S23.

[0077] Furthermore, when step S22 is executed after step S24, the signal processing unit 112 determines whether the total value calculated in step S24 is greater than the previous total value (i.e., the total value calculated in step S24 executed immediately before this step S24, or the total value calculated in step S21 or step S26). If the total value calculated in step S24 is greater than the previous total value, the process proceeds to step S25. If the total value calculated in step S24 is equal to or less than the previous total value, the process proceeds to step S23.

[0078] (Step S23) The signal processing unit 112 narrows the interval between the center frequency of the light source 113b of the optical transmitter 113 and the center frequency of the light source of the optical transmitter 114 by a predetermined interval.

[0079] Furthermore, the signal processing unit 112 generates a frame including path information of the transmission source. The optical transmitter 113 converts the frame including the path information of the transmission source (i.e., an electrical signal) into a transmission optical signal 1 while the center frequency of the light source 113b is changed. Similarly, the optical transmitter 114 converts the frame including the path information of the transmission source (i.e., an electrical signal) into a transmission optical signal 2 while the center frequency of the light source of the optical transmitter 114 is changed. The optical multiplexing / demultiplexing unit 120 multiplexes the transmission optical signal 1 and the transmission optical signal 2. The optical amplifying unit 130 amplifies the multiplexed optical signal. The optical communication device 100a transmits the amplified optical signal to the optical communication device 200a.

[0080] The optical communication device 200a receives the optical signal transmitted by the optical communication device 100a. The optical amplifier 230 amplifies the optical signal. The optical multiplexer / demultiplexer 220 demultiplexes the amplified optical signal. As a result, the amplified optical signal is demultiplexed into a received optical signal 11 and a received optical signal 12. The received optical signal 11 is input to the optical receiver 215. The received optical signal 12 is input to the optical receiver 216. The optical receiver 215 converts the received optical signal 11 into an electrical signal. The converted electrical signal is input to the signal processing unit 212. The optical receiver 216 converts the received optical signal 12 into an electrical signal. The converted electrical signal is input to the signal processing unit 212. The signal processing unit 212 calculates a BER1 of the electrical signal output by the optical receiver 215. The signal processing unit 212 calculates a BER2 of the electrical signal output by the optical receiver 216.

[0081] The signal processing unit 212 generates a frame including BER1. The signal processing unit 212 generates a frame including BER2. The optical transmitter 213 converts the frame including BER1 (i.e., an electrical signal) into a transmission optical signal 11. Similarly, the optical transmitter 214 converts the frame including BER2 (i.e., an electrical signal) into a transmission optical signal 12. The optical multiplexing / demultiplexing unit 220 controls the optical switch that the optical multiplexing / demultiplexing unit 220 has, using the path information. The optical multiplexing / demultiplexing unit 220 multiplexes the transmission optical signal 11 and the transmission optical signal 12. The optical amplifier 230 amplifies the multiplexed optical signal. The optical communication device 200a transmits the amplified optical signal to the optical communication device 100a.

[0082] (Step S24) The signal processing unit 112 acquires BER1 and BER2 via the optical receivers 115 and 116. The signal processing unit 112 adds BER2 to BER1. As a result, the sum of BER1 and BER2 is calculated. Then, the process proceeds to step S22.

[0083] (Step S25) The signal processing unit 112 determines whether or not step S26 has been executed. If step S26 has not been executed, the process proceeds to step S26. If step S26 has been executed, the process proceeds to step S27.

[0084] (Step S26) The signal processing unit 112 sets the roll-off factor α of the first RRC filter to a value greater than the previous roll-off factor α. The signal processing unit 112 also sets the center frequency of the light source 113b of the optical transmitter 113 to 188.4125 THz. That is, the signal processing unit 112 returns the center frequency of the light source 113b to the initial state.

[0085] The signal processing unit 112 sets the roll-off factor α of the second RRC filter to a value greater than the previous roll-off factor α. The signal processing unit 112 also sets the center frequency of the light source of the optical transmitter 114 to 188.4875 THz. That is, the signal processing unit 112 returns the center frequency of the light source of the optical transmitter 114 to the initial state.

[0086] The signal processing unit 112 generates a frame including path information of the transmission source. The optical transmitter 113 converts the frame including the path information of the transmission source (i.e., an electrical signal) into a transmission optical signal 1 while the roll-off rate α of the first RRC filter is changed. Similarly, the optical transmitter 114 converts the frame including the path information of the transmission source (i.e., an electrical signal) into a transmission optical signal 2 while the roll-off rate α of the second RRC filter is changed. The optical multiplexing / demultiplexing unit 120 multiplexes the transmission optical signal 1 and the transmission optical signal 2. The optical amplifying unit 130 amplifies the multiplexed optical signal. The optical communication device 100a transmits the amplified optical signal to the optical communication device 200a.

[0087] The optical communication device 200a receives the optical signal transmitted by the optical communication device 100a. The optical amplifier 230 amplifies the optical signal. The optical multiplexer / demultiplexer 220 demultiplexes the amplified optical signal. As a result, the amplified optical signal is demultiplexed into a received optical signal 11 and a received optical signal 12. The received optical signal 11 is input to the optical receiver 215. The received optical signal 12 is input to the optical receiver 216. The optical receiver 215 converts the received optical signal 11 into an electrical signal. The converted electrical signal is input to the signal processing unit 212. The optical receiver 216 converts the received optical signal 12 into an electrical signal. The converted electrical signal is input to the signal processing unit 212. The signal processing unit 212 calculates a BER1 of the electrical signal output by the optical receiver 215. The signal processing unit 212 calculates a BER2 of the electrical signal output by the optical receiver 216.

[0088] The signal processing unit 212 generates a frame including BER1. The signal processing unit 212 generates a frame including BER2. The optical transmitter 213 converts the frame including BER1 (i.e., an electrical signal) into a transmission optical signal 11. Similarly, the optical transmitter 214 converts the frame including BER2 (i.e., an electrical signal) into a transmission optical signal 12. The optical multiplexing / demultiplexing unit 220 controls the optical switch that the optical multiplexing / demultiplexing unit 220 has, using the path information. The optical multiplexing / demultiplexing unit 220 multiplexes the transmission optical signal 11 and the transmission optical signal 12. The optical amplifier 230 amplifies the multiplexed optical signal. The optical communication device 200a transmits the amplified optical signal to the optical communication device 100a.

[0089] The signal processing unit 112 acquires the BER1 and BER2 via the optical receivers 115 and 116. The signal processing unit 112 calculates the sum of the BER1 and BER2.

[0090] (Step S27) The signal processing unit 112 compares the total BER value that is the minimum value at the previous roll-off rate α (hereinafter referred to as the previous total BER value) with the total BER value that is the minimum value at the current roll-off rate α (hereinafter referred to as the current total BER value). The signal processing unit 112 determines whether or not the current total BER value is greater than the previous total BER value. If the current total BER value is greater than the previous total BER value, the process proceeds to step S28. If the current total BER value is equal to or less than the previous total BER value, the process proceeds to step S26.

[0091] (Step S28) The signal processing unit 112 sets the center frequency of the light source 113b of the optical transmitter 113 at the time of the previous total value of BER to the optical transmitter 113. The signal processing unit 112 sets the roll-off rate α at the time of the previous total value of BER to the first RRC filter. Furthermore, the signal processing unit 112 sets the center frequency of the light source of the optical transmitter 114 at the time of the previous total value of BER to the optical transmitter 114. The signal processing unit 112 sets the roll-off rate α at the time of the previous total value of BER to the second RRC filter.

[0092] In the first embodiment, a case has been described in which BER1 and BER2 are received by the optical communication device 100 via the control device 300. In the second embodiment, the optical communication device 200a transmits an optical signal including BER1 and BER2 to the optical communication device 100a, and the signal processing unit 112 acquires BER1 and BER2 via the optical receivers 115 and 116. As such, in the optical communication system of the second embodiment, the optical communication device 100a can receive BER1 and BER2 even without the control device 300. Therefore, the optical communication system of the second embodiment can be realized at a lower cost than the optical communication system of the first embodiment.

[0093] The features of the above-described embodiments can be combined with each other as appropriate. [Explanation of symbols]

[0094] 100, 100a Optical communication device, 101 Processor, 102 Volatile storage device, 103 Non-volatile storage device, 110 Transponder, 111 IF unit, 112 Signal processing unit, 113 Optical transmitter, 113a Control unit, 113b Light source, 113c Modulation unit, 114 Optical transmitter, 115 Optical receiver, 116 Optical receiver, 120 Optical multiplexing / demultiplexing unit, 130 Optical amplification unit, 140 Control unit, 200, 200a Optical communication device, 210 Transponder, 211 IF unit, 212 Signal processing unit, 213 Optical transmitter, 214 Optical transmitter, 215 Optical receiver, 216 Optical receiver, 220 Optical multiplexing / demultiplexing unit, 230 Optical amplification unit, 240 Control unit, 300 control device, 900 transponder, 901 IF unit, 902 signal processing unit, 903_1, 903_2,...,903_n optical transmitters, 904_1, 904_2,...,904_n optical receivers.

Claims

1. a first optical communication device having a transponder including a first optical transmitter having a first light source, a second optical transmitter having a second light source, and a plurality of optical receivers; and a signal processing unit having a first low-pass filter function for an electrical signal input to the first optical transmitter and a second low-pass filter function for an electrical signal input to the second optical transmitter; a second optical communication device that calculates a first bit error rate of data based on an optical signal transmitted by the first optical transmitter and calculates a second bit error rate of data based on an optical signal transmitted by the second optical transmitter; Including, The signal processing unit detecting a first combination of the roll-off rate of the first low-pass filter and the center frequency of the first light source, which minimizes the sum of the first bit error rate and the second bit error rate, and a second combination of the roll-off rate of the second low-pass filter and the center frequency of the second light source, which minimizes the sum of the first bit error rate and the second bit error rate; setting a center frequency of the first light source in the first optical transmitter based on the first combination; setting a roll-off rate of the first low-pass filter based on the first combination; setting a center frequency of the second light source in the second optical transmitter based on the second combination; setting a roll-off rate of the second low-pass filter based on the second combination; Optical communication system.

2. the transponder has three or more optical transmitters including the first optical transmitter and the second optical transmitter; the center frequency of the first light source is the smallest among the center frequencies of the light sources of the three or more optical transmitters; the center frequency of the second light source is the largest among the center frequencies of the light sources of the three or more optical transmitters; 2. The optical communication system according to claim 1.

3. a control device that receives the first bit error rate and the second bit error rate from the second optical communication device and transmits the first bit error rate and the second bit error rate to the first optical communication device; 3. The optical communication system according to claim 1 or 2.

4. the second optical communication device transmits an optical signal including the first bit error rate and the second bit error rate to the first optical communication device; the signal processing unit acquires the first bit error rate and the second bit error rate via the plurality of optical receivers.

3. The optical communication system according to claim 1 or 2.

5. An optical communication device that is a first optical communication device in a communication system in which a first optical communication device and a second optical communication device communicate with each other, a transponder including a first optical transmitter having a first light source, a second optical transmitter having a second light source, and a plurality of optical receivers; and a signal processing unit having a first low-pass filter function for an electrical signal input to the first optical transmitter and a second low-pass filter function for an electrical signal input to the second optical transmitter; The signal processing unit a first bit error rate calculated by the second optical communication device from data based on the optical signal transmitted by the first optical transmitter; and a second bit error rate calculated by the second optical communication device from data based on the optical signal transmitted by the second optical transmitter; detecting a first combination, which is a combination of the roll-off rate of the first low-pass filter and the center frequency of the first light source, and a second combination, which is a combination of the roll-off rate of the second low-pass filter and the center frequency of the second light source, when the sum is minimum; setting a center frequency of the first light source in the first optical transmitter based on the first combination; setting a roll-off rate of the first low-pass filter based on the first combination; setting a center frequency of the second light source in the second optical transmitter based on the second combination; setting a roll-off rate of the second low-pass filter based on the second combination; Optical communication equipment.

6. The transponder has three or more optical transmitters including the first optical transmitter and the second optical transmitter; the center frequency of the first light source is the smallest among the center frequencies of the light sources of the three or more optical transmitters; the center frequency of the second light source is the largest among the center frequencies of the light sources of the three or more optical transmitters; 6. The optical communication device according to claim 5.

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