JP6127568B2 - Optical receiver, optical reception method, and optical communication system - Google Patents

Description

  The present invention relates to a technique for receiving an optical signal.

  In recent years, 100 Gbps Ethernet, which is being commercialized as the next generation Ethernet (registered trademark), performs 25 Gbps × 4 ch WDM (Wavelength Division Multiplexing) transmission.

  In the transmission standard of 100 Gigabit Ethernet, there are specifications such as a transmission distance of 40 km and 10 km. In a 40 km standard optical receiver, for example, an optical signal output from an optical transmitter is transmitted through a short optical fiber over a short distance from a weak optical power optical signal transmitted over a long distance over an optical fiber of about 40 km. Receiving optical signals with low optical power. For this reason, an optical receiver with a wide dynamic range is required in 100 Gigabit Ethernet.

  In order to meet the above requirements, the optical receiver is provided with an optical amplifier at the input stage, amplifies the optical power of the optical signal received from the optical transmitter, and converts the optical power of the optical signal output from the optical amplifier to the photo-electric power at the subsequent stage. Techniques are used to keep the dynamic range of the diode. In the following description, the dynamic range of the photodiode is also referred to as a light receiving range of the photodiode.

  In an optical amplifier using a related technique, a part of the amplified signal light of a single channel or a plurality of channels having a wavelength with the highest gain is detected from the optical amplifier output. A technique is known for controlling the gain of an optical amplifier so that the output of the optical amplifier becomes constant using the detected output.

  In addition, in an optical amplifier using a related technique, the level of each signal light is individually monitored for both input light and output light, and the gain of the optical amplifying unit for each signal light is individually detected. The optical amplifier guarantees the minimum gain of the optical amplifying unit by controlling the gain of the signal light having the smallest gain to be constant. Furthermore, a technique is known in which the optical amplifier guarantees the maximum gain of the optical amplifying unit by controlling the gain of the signal light having the largest gain to be constant.

  In an optical amplifier using a related technique, a monitor unit for monitoring a gain difference between wavelengths is provided in one of the optical amplification repeaters, and the gain difference between the wavelengths is fed back to each terminal station. To do. In each terminal station, a technique is known in which the monitor control unit drives the output control unit based on the received gain difference information to adjust the transmission level of each wavelength (see, for example, Patent Documents 1 to 3). .

Patent No. 2934500 Japanese Patent Laid-Open No. 10-173266 Japanese Patent Laid-Open No. 5-292033

  In the reception technique described above, when an optical amplifier having a wavelength dependency of the gain is used in the optical receiver, when the optical receiver receives a communication signal obtained by multiplexing optical signals of different wavelengths, the optical amplifier varies depending on the wavelength. A power optical signal is output. Therefore, in the optical receiver, all of the optical powers of a plurality of different optical signals must be within the light receiving range of the photodiode, and there is a problem that the dynamic range of the optical receiver becomes narrow.

  In view of the above-described problems, an optical receiver described later in this specification is intended to realize a wide dynamic range in an optical receiver using an optical amplifier whose wavelength is dependent on gain.

One of the optical receivers disclosed in this specification is an optical receiver including an optical amplification unit, a demultiplexing unit, a monitor unit, a detection unit, and a control unit. Here, when a communication signal obtained by multiplexing a plurality of optical signals having different wavelengths is input to the optical amplifying unit, the optical power of the communication signal is amplified and output. The demultiplexing unit demultiplexes the communication signal and outputs a plurality of optical signals when the communication signal whose optical power is amplified by the optical amplification unit is input. The monitor unit measures the optical power of each of the plurality of optical signals output from the demultiplexing unit. The detection unit is configured to calculate a maximum optical power value, a minimum optical power value, and an optical power difference that is a difference between the maximum optical power value and the minimum optical power value from the optical power values of the plurality of optical signals measured by the monitor unit. Is detected. The control unit controls the gain of the optical amplification unit. In this control unit, the optical power difference in a state where the gain of the optical amplification unit is adjusted to the initial value at the start of the control is the first target value, which is the target value of the maximum optical power value, and the minimum optical power. When the optical power difference threshold is larger than the second target value, which is the target value of the value, the gain of the optical amplifying unit is adjusted so that the minimum optical power value becomes the second target value. In addition, when the optical power difference in the state where the gain of the optical amplifying unit is adjusted to the initial value at the start of the control is equal to or less than the optical power difference threshold value, the control unit sets the maximum optical power value to the first value. If the gain is larger than the target value, the gain of the optical amplifying unit is adjusted so that the maximum optical power value becomes the first target value. If the maximum optical power value is equal to or less than the first target value, the initial value state is maintained. Controls the gain of the optical amplifier.

  According to the above aspect, a wide dynamic range can be realized in an optical receiver using an optical amplifier having a wavelength dependency in gain.

It is a figure which shows one Example of the optical communication system in which an optical receiver is used. It is a functional block diagram which shows one Example of an optical receiver. It is a figure which shows a setting value table. It is a block diagram which shows one Example of an optical receiver. It is a figure which shows an example of the input-output characteristic of an optical amplifier. It is a figure which shows an example of the input-output characteristic of an optical amplifier. It is a figure which shows an example of the control current value of an optical amplifier. It is a flowchart which shows the processing content of the gain control of an optical amplifier.

[Embodiment]
The optical receiver of the embodiment will be described.
The optical receiver of the embodiment supports wavelength division multiplexing communication. The wavelength division multiplex communication is a communication method for transmitting and receiving a communication signal obtained by multiplexing a plurality of optical signals having different wavelengths. Hereinafter, the optical receiver of the embodiment is also simply referred to as an optical receiver.

The optical receiver has functions of an optical amplification unit, a demultiplexing unit, a conversion unit, a monitor unit, a detection unit, a control unit, a storage unit, and a supply unit.
When the optical receiver receives the communication signal, the optical amplifier included in the input stage amplifies a plurality of optical signals included in the communication signal. In the following description, collectively amplifying a plurality of optical signals included in a communication signal is simply referred to as amplifying the communication signal.

The communication signal amplified by the optical amplification unit is demultiplexed into a plurality of optical signals by the demultiplexing unit. The plurality of demultiplexed optical signals are converted into electrical signals by the conversion unit and output to the monitor unit.
The monitor unit measures the optical power values of a plurality of optical signals from the power values of the input electrical signals.

  The detection unit detects a maximum optical power value that is a maximum value of the optical power values of a plurality of optical signals included in the communication signal. The detection unit detects a minimum optical power value that is a minimum value of the optical power values of the plurality of optical signals included in the communication signal. Furthermore, the detection unit detects an optical power difference that is a difference between the maximum optical power value and the minimum optical power value.

The storage unit is a difference between the first target value that is the target value of the maximum optical power value, the second target value that is the target value of the minimum optical power value, and the first target value and the second target value. The optical power difference threshold value is stored.
The supply unit is controlled by the control unit and supplies a control current for controlling the gain of the optical amplification unit to the optical amplification unit.

  The control unit controls the supply unit to set the maximum optical power value to the first target value when the optical power difference is equal to or smaller than the optical power difference threshold and the maximum optical power value is larger than the first target value. As described above, the gain of the optical amplifying unit is adjusted by changing the magnitude of the control current. Further, when the optical power difference is larger than the optical power difference threshold value, the control unit controls the supply unit to change the magnitude of the control current so that the minimum optical power value becomes the second target value. Adjust the gain of the optical amplifier.

  As described above, the optical receiver according to the embodiment measures the optical power of a plurality of optical signals output from the optical amplifier, and the optical power of each optical signal output from the optical amplifier falls within the light receiving range of the photodiode. Thus, the gain of the optical amplifier is adjusted. As a result, the optical receiver suppresses the optical power of the optical signal having the maximum optical power within the light receiving range, and avoids that the optical power of the optical signal having the minimum optical power becomes smaller than the light receiving range of the photodiode. To do. Therefore, the optical receiver can realize a wide dynamic range even when a semiconductor optical amplifier having a wavelength dependency is used for the gain of the optical amplifier that adjusts the optical power of the optical signal input to the photodiode.

FIG. 1 is a diagram showing an embodiment of an optical communication system in which an optical receiver is used.
An optical communication system 100 to which the optical receiver of the embodiment is applied will be described with reference to FIG.
An optical communication system 100 illustrated in FIG. 1 includes an optical transmitter 110, an optical receiver 120, and an optical fiber 130.

The optical transmitter 110 includes drivers (Drv) 10 to 1n, laser diodes (LD) 20 to 2n, and a multiplexer 3 (multiplexing unit).
When a data signal is input from an information processing device or an input device (not shown), the drivers 10 to 1n generate a modulation signal that modulates an optical carrier output from the laser diodes 20 to 2n, and the generated modulation signal is converted into a laser diode. Output to 20-2n.

  Each of the laser diodes 20 to 2n generates optical carriers having different wavelengths. Each optical carrier is modulated by a modulator (not shown) according to a modulation signal input from the drivers 10 to 1n, and input to the multiplexer 3 as an optical signal representing a data signal. Note that the optical receiver 120 of 100 Gigabit Ethernet uses, for example, 25 Gbps × 4ch WDM transmission and uses four laser diodes with a frequency interval of 800 GHz.

  The multiplexer 3 multiplexes a plurality of optical signals having different wavelengths input from the laser diodes 20 to 2n, generates a communication signal, and outputs the communication signal to the optical fiber 130. As a result, the optical transmitter 110 transmits a communication signal to the optical receiver 120.

The optical receiver 120 includes an optical amplifier 4, a duplexer 5, and photodiodes (PDs) 60 to 6n.
When a communication signal is input via the optical fiber 130, the optical amplifier 4 amplifies the optical power of the communication signal. That is, the optical amplifier 4 collectively amplifies the optical power of a plurality of optical signals included in the communication signal. Further, the optical amplifier 4 is, for example, a semiconductor optical amplifier (SOA: Semiconductor Optical Amplifier). In the following description, a configuration in which a semiconductor optical amplifier is provided in the optical receiver 120 of the embodiment will be described.

  The demultiplexer 5 demultiplexes the amplified communication signal input from the optical amplifier 4 into a plurality of optical signals. The duplexer 5 outputs the demultiplexed optical signals to the photodiodes 60 to 6n, respectively.

  When an optical signal is input from the duplexer 5, the photodiodes 60 to 6 n generate current signals (electric signals) having a magnitude corresponding to the magnitude of the optical power of the optical signal. The photodiodes 60 to 6n output current signals to an information processing device (not shown). For example, Pin-PD or PN-PD is used for the photodiodes 60 to 6n.

  The optical fiber 130 connects the optical transmitter 110 and the optical receiver 120 so that they can communicate with each other. The optical fiber 130 is not particularly limited, but for example, a single mode fiber may be used.

FIG. 2 is a functional block diagram showing an embodiment of the optical receiver.
The optical receiver 120 illustrated in FIG. 2 includes an optical amplification unit 201, a demultiplexing unit 202, a conversion unit 203, a monitor unit 204, a detection unit 205, a storage unit 206, a control unit 207, and a supply unit 208.

  The optical amplifying unit 201 is provided at the input stage of the optical receiver 120, and when a communication signal transmitted from the optical transmitter 110 is input, a plurality of optical signals having different wavelengths included in the communication signal are collectively amplified. Further, the gain of the optical amplifying unit 201 changes according to the magnitude of the control current input from the supply unit 208. As an example, when a semiconductor optical amplifier is applied to the optical amplification unit 201, the gain of the optical amplification unit 201 is proportional to the magnitude of the control current input from the supply unit 208. The optical amplification unit 201 is, for example, the optical amplifier 4 in FIG.

When the communication signal whose optical power is amplified by the optical amplifier 201 is input, the demultiplexing unit 202 demultiplexes the communication signal and outputs an optical signal having a plurality of wavelengths.
The conversion unit 203 converts the optical signals having a plurality of wavelengths output from the demultiplexing unit 202 into electrical signals corresponding to the respective optical powers. The conversion unit 203 is, for example, the photodiodes 60 to 6n in FIG. 1, and a light receiving range is set as a range that can be accurately converted into an electric signal indicating a received optical signal.

  The monitor unit 204 measures the optical powers of the optical signals having a plurality of wavelengths output from the demultiplexing unit 202. The monitor unit 204 may measure the optical power of the optical signal by monitoring the current value of the electrical signal input from the conversion unit 203, for example. The monitor unit 204 may measure the optical power of the optical signal by monitoring the magnitude of the amplitude of the electric signal input from the conversion unit 203.

  The detection unit 205 determines the maximum optical power value, the minimum optical power value, the maximum optical power value, and the minimum optical power from the optical power value that is the magnitude of the optical power of the optical signals having a plurality of wavelengths measured by the monitor unit 204. An optical power difference that is a difference from the value is detected.

  The maximum optical power value is the largest optical power value among the optical power values of the optical signals having a plurality of wavelengths measured by the monitor unit 204. The minimum optical power value is the smallest optical power value among the optical power values of a plurality of optical signals measured by the monitor unit 204.

The storage unit 206 stores a setting value table 300 illustrated in FIG.
The set value table 300 includes a target value P1 (first target value) for the maximum optical power value, a target value P2 (second target value) for the minimum optical power value, and the target value P1 and the target value P2. The optical power difference threshold value P3 that is the difference and the initial value I0 of the control current when the adjustment of the gain of the optical amplifying unit 201 is stored are stored.

  The target value P1 and the target value P2 are set so as to fall within the light receiving range of the conversion unit 203. As an example, when the light receiving range of the conversion unit 203 is −10 dBm (minimum received power) to +5 dBm (maximum received power), the target value P1 may be set to −2 dBm and the target value P2 may be set to −8 dBm. The target values P1 and P2 may be set with a margin between the light receiving range of the conversion unit 203. As a result, even when an error occurs in gain control described later, the optical receiver 120 absorbs the error with a margin, and the maximum optical power and the minimum optical power of the optical signals of a plurality of wavelengths output from the optical amplifying unit 201. Can be within the light receiving range of the conversion unit 203.

The optical power difference threshold value P3 is a value obtained by subtracting the target value P2 from the target value P1. That is, the optical power difference threshold P3 is a difference in optical power between the target value P1 and the target value P2.
The initial value I0 is set so that, for example, the optical power to be output falls within the light receiving range of the conversion unit 203 when the optical power having the minimum reception power in the dynamic range required by the optical receiver 120 is received.

  The control unit 207 acquires the maximum optical power value, minimum optical power value, and optical power difference detected by the detection unit 205. In addition, the control unit 207 acquires the target value P1, the target value P2, the optical power difference threshold value P3, and the initial value I0 stored in the setting value table 300 stored in the storage unit 206.

  Then, the control unit 207, when the optical power difference is equal to or smaller than the optical power difference threshold P3 and the maximum optical power value is larger than the target value P1, causes the optical amplifying unit to set the maximum optical power value to the target value P1. The gain of 201 is adjusted. At this time, the control unit 207 controls the supply unit 208 while referring to the maximum optical power value detected by the detection unit 205 to reduce the magnitude of the control current, and sets the maximum optical power value to the target value. Set to P1. In addition, when the optical power values of the plurality of optical signals are all between the target value P1 and the target value P2, the control unit 207 makes the gain of the optical amplification unit 201 constant. That is, the control unit 207 controls the supply unit 208 to keep the control current constant when the optical power values of the plurality of optical signals are all between the target value P1 and the target value P2.

  Further, the control unit 207 adjusts the gain of the optical amplification unit 201 so that the minimum optical power value becomes the target value P2 when the optical power difference is larger than the optical power difference threshold P3. At this time, the control unit 207 controls the supply unit 208 while referring to the minimum optical power value detected by the detection unit 205 to increase the magnitude of the control current, and sets the maximum optical power value to the target value. Set to P2. In addition, when the optical power values of the plurality of optical signals are all between the target value P1 and the target value P2, the control unit 207 makes the gain of the optical amplification unit 201 constant. That is, the control unit 207 controls the supply unit 208 to keep the control current constant when the optical power values of the plurality of optical signals are all between the target value P1 and the target value P2.

When the gain adjustment of the optical amplifying unit 201 is started, the control unit 207 determines the magnitude of the gain, and when the optical signal having the optical power of the minimum reception power of the optical receiver 120 is input to the optical amplifier 4, the optical amplifier 4 so that the optical power of the optical signal output from 4 falls within the light receiving range of the converter 203. At this time, for example, the control unit 207 acquires the initial value I0 from the setting value table 300, controls the supply unit 208, and supplies the optical amplification unit 201 with the control current of the initial value I0. Then, when the optical power values of the plurality of optical signals are all between the target value P1 and the target value P2, the control unit 207 controls the supply unit 208 to make the control current constant at the initial value I0.
The supply unit 208 supplies a control current for controlling the gain to the optical amplification unit 201.

FIG. 4 is a block diagram showing an embodiment of the optical receiver.
The optical receiver 120 illustrated in FIG. 4 includes an optical amplifier 4, a duplexer 5, photodiodes 60 to 6n, power monitors 70 to 7n, a control circuit 8, a storage device 9, and a supply circuit 41. The description of the same configuration as in FIG. 1 is omitted.

The optical amplifier 4 functions as the optical amplification unit 201 in FIG.
The duplexer 5 functions as the demultiplexing unit 202 in FIG.
The photodiodes 60 to 6n function as the conversion unit 203 in FIG.
The power monitors 70 to 7n are power meters, for example, and function as the monitor unit 204 of FIG.

  The control circuit 8 is, for example, a CPU, a multi-core CPU, an FPGA (Field Programmable Gate Array), a PLD (Programmable Logic Device), or the like. The maximum optical power value detection circuit 81, the minimum optical power value detection circuit 82, and the optical power difference detection circuit 83 of the control circuit 8 function as the detection unit 205 in FIG. The control switching circuit 84 of the control circuit 8 functions as the control unit 207 in FIG. Further, the control circuit 8 outputs an optical power value input as an analog signal from the power monitors 70 to 7n to a digital signal, and outputs a digital signal from the control switching circuit 84. And a D / A conversion circuit 86 for converting the control current value into an analog signal.

The storage device 9 stores various data. The storage device 9 is, for example, a ROM (Read Only Memory) and a RAM (Random Access Memory). The RAM may be used as a work area for the control circuit 8. The ROM may store a program for causing the control circuit 8 to function as the detection unit 205 and the control unit 207 and a setting value table 300. The storage device 9 functions as the storage unit 206 in FIG.
The supply circuit 41 is a power supply having a current adjustment circuit, for example. The supply circuit 41 functions as the supply unit 208 in FIG.

5 and 6 are diagrams showing examples of input / output characteristics of the optical amplifier.
FIG. 7 is a diagram illustrating an example of the control current value of the optical amplifier.
In the following description, it is assumed that a semiconductor optical amplifier is applied to the optical amplifier 4 of the optical receiver 120. As an example, it is assumed that the dynamic range required for the optical receiver 120 is 25 dBm, and the range is −20 dBm to +5 dBm. Furthermore, it is assumed that the light receiving range of the conversion unit 203 is −10 dBm to +2 dBm. The values set in FIG. 3 are used as the target value P1, the target value P2, the optical power difference threshold value P3, and the initial value I0.

  L0 to L3 shown in FIGS. 5 and 6 indicate input / output characteristics of optical signals (communication signals) of a plurality of wavelengths input to the optical amplifier 4, respectively. 5 and 6 indicate the optical power of the optical signal input to the optical amplifier 4. 5 and 6 indicate the optical power of the optical signal output from the optical amplifier 4.

The horizontal axis in FIG. 7 indicates the optical power input to the optical amplifier 4. The vertical axis in FIG. 7 indicates the magnitude of the control current.
With reference to the input / output characteristics of the optical amplifier of FIG. 5 and the control current value of the optical amplifier of FIG. 7, the gain control of the optical amplifier 4 that adjusts the maximum optical power value (hereinafter also referred to as maximum gain control). explain.
In the following description, reference is made to the functional blocks of FIG. The optical amplification unit 201 is the optical amplifier 4.

  As shown in FIGS. 5 and 7, the initial value I0 (120 mA) is the average optical power output when the optical power of the minimum receiving power (−20 dBm) in the dynamic range required for the optical receiver 120 is received. Thus, the value is set to be −5.5 dBm.

  Then, the control unit 207 supplies the initial value I0 to the optical amplification unit 201 when the optical power of the communication signal input to the optical amplification unit 201 is −20 dBm to −15 dBm. Thus, the control unit 207 uses the optical power output from the optical amplifying unit 201 (−5.5 dBm to −2 dBm) when the optical power of the communication signal input to the optical amplifying unit 201 is −20 dBm to −15 dBm. The light receiving range of the conversion unit 203 can be included.

  When the optical power of the communication signal input to the optical amplifying unit 201 is greater than −15 dBm, when the current of the initial value I0 is input to the optical amplifying unit 201, the maximum optical power value output from the optical amplifying unit 201 is the target It becomes larger than the value P1 (−2 dBm).

  Then, as shown in FIGS. 5 and 7, the control unit 207 controls the supply unit 208 to change the current supplied to the optical amplification unit 201 in order to set the maximum optical power value to the target value P <b> 1. The gain of the unit 201 is adjusted. At this time, the control unit 207 changes the control current supplied to the optical amplification unit 201 while referring to the maximum optical power value measured by the monitor unit 204. Note that the control current change by the control unit 207 may be changed, for example, by a current value dI having a necessary resolution predetermined in an experiment. Then, every time the current value dI of the control current is changed, the control unit 207 determines whether or not the maximum optical power value has reached the target value P1, and when the maximum optical power value has reached the target value P1 The control current may be constant.

  By performing the above control, as shown in FIG. 5, the optical receiver 120 changes the optical power of the optical signal output from the optical amplifying unit 201 within the range of −20 dBm to +0 dBm to the target values P1 to P1. It can be within the range of the target value P2. Further, the range of the target value P1 to the target value P2 is set narrower than −10 dBm to +2 dBm, which is the light receiving range of the conversion unit 203. As a result, the optical receiver 120 can amplify the optical power of the optical signals of a plurality of wavelengths by the optical amplifying unit 201 with a margin in the range of 20 dBm within the required dynamic range, and can receive the communication signal. .

With reference to the input / output characteristics of the optical amplifier of FIG. 6 and the solid line of the control current value of the optical amplifier of FIG. 7, the gain of the optical amplifying unit 201 of the embodiment that adjusts the maximum optical power value and the minimum optical power value The control will be described.
When the optical power of the communication signal input to the optical amplifying unit 201 is −20 dBm to 0 dBm, the gain control of the embodiment is the same as the maximum gain control described with reference to FIGS.

  When the maximum gain control is executed when the optical power of the communication signal input to the optical amplifier 201 is greater than 0 dBm, the minimum optical power value (L0) output from the optical amplifier 201 is as shown in FIG. , Becomes smaller than the target value P2. That is, when the maximum gain control is executed when the optical power of the communication signal input to the optical amplifier 201 is greater than 0 dBm, the maximum optical power value (L3) and the minimum optical power value are larger than the optical power difference threshold P3. The optical power difference increases.

  Therefore, as shown in FIG. 7, the control unit 207 controls the supply unit 208 to change the control current supplied to the optical amplification unit 201 in order to set the minimum optical power value to the target value P <b> 2. The gain of the unit 201 is adjusted. At this time, the control unit 207 changes the current supplied to the optical amplification unit 201 while referring to the minimum optical power value measured by the monitor unit 204. Note that the control current change by the control unit 207 may be changed, for example, by a current value −dI having a necessary resolution predetermined in an experiment. The control unit 207 determines whether or not the minimum optical power value becomes the target value P2 every time the current value of the control current is changed to the current value −dI, and the minimum optical power value becomes the target value P2. Sometimes, the control current may be constant.

  By performing the above control, as shown in FIG. 6, the optical receiver 120 changes the optical power of the optical signal output from the optical amplifying unit 201 within the range of −25 dBm to +5 dBm to the target values P1 to P1. It can be within the range of the target value P2. Further, the range of the target value P1 to the target value P2 is set narrower than −10 dBm to +2 dBm, which is the light receiving range of the conversion unit 203. Accordingly, the optical receiver 120 can receive a communication signal by amplifying the optical power of the optical signals of a plurality of wavelengths by the optical amplifying unit 201 with a margin in a range of 25 dBm within the required dynamic range. .

FIG. 8 is a flowchart showing the processing contents of the gain control of the optical amplifier.
With reference to FIG. 8, the processing content of the gain control of the optical amplifier will be described.
In the following description, reference is made to the functional blocks of FIG.

  The detection unit 205 refers to the optical power value of each optical wavelength included in the communication signal measured by the monitor unit 204, and determines the maximum optical power value (Pmax), the minimum optical power value (Pmin), and the optical power difference (dP). ) Is detected (S1).

Then, the control unit 207 compares the optical power difference detected by the detection unit 205 with the optical power difference threshold value P3 (S2).
When the optical power difference is larger than the optical power difference threshold P3 (Yes in S2), the control unit 207 determines the control parameter as the minimum optical power value and the control target as the target value P2 (S3). Then, the control unit 207 controls the control current (ISOA) so that the minimum optical power value becomes the target value P2 (S4).

  Then, the control unit 207 determines whether or not to end the gain control (S5). When it is determined that the gain control is to be ended (Yes in S5), the control unit 207 ends the series of processes. Note that the control unit 207 performs gain control, for example, when a signal indicating the end of gain control is input by the user or when communication with the optical transmitter 110 ends in the process before S5. It may be determined to end.

  Further, when it is determined that the gain control is to be continued, the control unit 207 executes the process of S1. Note that the control unit 207 may determine to continue gain control when there is no request for termination of gain control from a user or an information processing apparatus (not shown) in the process before S5, for example. Further, for example, the control unit 207 may change the control current in the process of S4 and execute the process of S1 after a predetermined time has elapsed. As a result, the control unit 207 can reduce the number of times of a series of processes according to the accuracy of gain control required, and can reduce the processing load.

When the optical power difference is smaller than the optical power difference threshold P3 in S2 (No in S2), the control unit 207 compares the maximum optical power value detected by the detection unit 205 with the target value P1 (S6). .
When the maximum optical power value is larger than the target value P1 (Yes in S6), the control unit 207 determines the control parameter as the maximum optical power value and the control target as the target value P1 (S7). Then, the control unit 207 controls the control current so that the maximum optical power value becomes the target value P1 (S4). And the control part 207 performs the process of S5.

  When the maximum optical power value is smaller than the target value P1 in S6 (No in S6), the control parameter is determined as the control current, and the control target is determined as the initial value I0 (S8). Then, the control unit 207 controls the control current so that the control current becomes the initial value I0 (S4). And the control part 207 performs the process of S5.

  As described above, the optical receiver 120 according to the embodiment measures the optical power of the optical signals having a plurality of wavelengths output from the demultiplexing unit 202 so that each optical power is within the light receiving range of the photodiodes 60 to 6n. Then, the gain of the optical amplifier is adjusted. Thereby, the optical receiver 120 suppresses the optical power of the optical signal having the maximum optical power within the light receiving range, and the optical power of the optical signal having the minimum optical power becomes smaller than the light receiving range of the photodiode. To avoid. Therefore, the optical receiver can realize a wide dynamic range even if a semiconductor optical amplifier having wavelength dependency is used for the optical receiver 120 that adjusts the optical power of the optical signal input to the photodiode.

  The optical receiver 120 of the embodiment can realize a wide dynamic range even when a semiconductor optical amplifier is applied to the optical amplifier 4 as described with reference to FIG. Therefore, the optical amplifier 4 of the embodiment can use a semiconductor optical amplifier instead of a fiber optical amplifier in the 100 Giga Ethernet 40 km standard, and the optical receiver 120 can be downsized.

The following additional notes are further disclosed with respect to the embodiments including the examples described above. Note that the present invention is not limited to the following supplementary notes.
(Appendix 1)
When a communication signal obtained by multiplexing a plurality of optical signals having different wavelengths is input, an optical amplification unit that amplifies and outputs the optical power of the communication signal;
A demultiplexing unit that demultiplexes the communication signal and outputs the plurality of optical signals when the communication signal with the optical power amplified by the optical amplification unit is input;
A monitor unit for measuring the optical power of each of the plurality of optical signals output from the demultiplexing unit;
From the optical power values of the plurality of optical signals measured by the monitor unit, a maximum optical power value, a minimum optical power value, and an optical power difference that is a difference between the maximum optical power value and the minimum optical power value are detected. A detector to
The optical power difference is equal to or less than an optical power difference threshold that is a difference between a first target value that is a target value of the maximum optical power value and a second target value that is a target value of the minimum optical power value; When the maximum optical power value is larger than the first target value, the gain of the optical amplification unit is adjusted so that the maximum optical power value becomes the first target value,
A control unit that adjusts the gain of the optical amplification unit so that the minimum optical power value is set to the second target value when the optical power difference is larger than the optical power difference threshold;
An optical receiver comprising:
(Appendix 2)
The controller is
The supplementary note 1 is characterized in that, when the optical power values of the plurality of optical signals are all between the first target value and the second target value, the gain of the optical amplification unit is made constant. Optical receiver.
(Appendix 3)
The optical receiver further includes:
A conversion unit that converts the plurality of optical signals output from the demultiplexing unit into electrical signals corresponding to respective optical powers;
The controller is
When the adjustment of the gain of the optical amplifying unit is started, the magnitude of the gain is output from the optical amplifier when an optical signal having the optical power of the minimum reception power of the optical receiver is input to the optical amplifier. The optical receiver according to appendix 1 or 2, wherein the optical power of the optical signal is set to a magnitude that falls within a light receiving range of the converter.
(Appendix 4)
A supply unit for supplying a control current for controlling the gain to the optical amplification unit;
A storage unit that stores an initial value that is a current value of a control current when starting to adjust the gain of the optical amplification unit;
With
The optical amplification unit is
The gain changes according to the magnitude of the control current,
The controller is
4. The optical receiver according to appendix 2 or 3, wherein when the adjustment of the gain of the optical amplifying unit is started, the supplying unit is controlled to supply the control current having the initial value to the optical amplifying unit. .
(Appendix 5)
The optical amplification unit is
The gain changes according to the magnitude of the control current,
The controller is
The optical receiver according to any one of appendices 1 to 4, wherein when the gain of the optical amplifying unit is adjusted, the magnitude of the control current is changed (Appendix 6).
A storage unit for storing the first target value, the second target value, and the optical power difference threshold;
The controller is
The first target value, the second target value, and the optical power difference threshold stored in the storage unit are used when changing the magnitude of the control current. The optical receiver as described in any one of.
(Appendix 7)
The optical receiver further includes:
A conversion unit that converts the plurality of optical signals output from the demultiplexing unit into electrical signals corresponding to respective optical powers;
The monitor unit is
The optical receiver according to claim 1, wherein the optical power of the optical signal is measured by monitoring a current value of the electrical signal.
(Appendix 8)
A conversion unit that converts the plurality of optical signals output from the demultiplexing unit into electrical signals corresponding to respective optical powers;
The monitor unit is
The optical receiver according to claim 1, wherein the optical power of the optical signal is measured by monitoring the amplitude of the electrical signal.
(Appendix 9)
The optical amplification unit is
9. The optical receiver according to claim 1, wherein the optical receiver is a semiconductor amplifier.
(Appendix 10)
The detection unit and the control unit are:
The optical receiver according to claim 1, wherein the optical receiver is executed by a CPU.
(Appendix 11)
When a communication signal obtained by multiplexing a plurality of optical signals having different wavelengths is input, the optical power of the communication signal is amplified,
Demultiplexing the communication signal in which the optical power is amplified;
Measure the optical power of each of the plurality of optical signals demultiplexed by the process of demultiplexing the communication signal,
From the measured optical power values of the plurality of optical signals, the maximum optical power value, the minimum optical power value, and the optical power difference that is the difference between the maximum optical power value and the minimum optical power value,
The optical power difference is equal to or less than an optical power difference threshold that is a difference between a first target value that is a target value of the maximum optical power value and a second target value that is a target value of the minimum optical power value; A gain for amplifying the communication signal in the process of amplifying the optical power of the communication signal so that the maximum optical power value becomes the first target value when the maximum optical power value is larger than the first target value. Adjust
When the optical power difference is larger than the optical power difference threshold, the communication signal is amplified in the process of amplifying the optical power of the communication signal so that the minimum optical power value is set to the second target value. An optical receiving method comprising adjusting a gain.
(Appendix 12)
The optical transmitter
When a plurality of optical signals having different wavelengths are input, a multiplexing unit that outputs a communication signal obtained by multiplexing the plurality of optical signals is provided.
The optical receiver
When a communication signal transmitted from the optical transmitter is input, an optical amplification unit that amplifies and outputs the optical power of the communication signal;
A demultiplexing unit that demultiplexes the communication signal and outputs the plurality of optical signals when the communication signal with the optical power amplified by the optical amplification unit is input;
A monitor unit for measuring the optical power of each of the plurality of optical signals output from the demultiplexing unit;
With reference to the optical power values of the plurality of optical signals measured by the monitor unit, a maximum optical power value, a minimum optical power value, and an optical power difference that is a difference between the maximum optical power value and the minimum optical power value; A detection unit for detecting
The optical power difference is equal to or less than an optical power difference threshold that is a difference between a first target value that is a target value of the maximum optical power value and a second target value that is a target value of the minimum optical power value; When the maximum optical power value is larger than the first target value, the gain of the optical amplification unit is adjusted so that the maximum optical power value becomes the first target value,
A control unit that adjusts the gain of the optical amplification unit so that the minimum optical power value is set to the second target value when the optical power difference is larger than the optical power difference threshold;
An optical communication system comprising:

10 to 1n driver 20 to 2n laser diode 3 multiplexer 4 optical amplifier 41 supply circuit 5 duplexer 60 to 6n photodiode 70 to 7n power monitor 8 control circuit 81 maximum optical power value detection circuit 82 minimum optical power value detection circuit 83 Optical power difference detection circuit 84 Control switching circuit 85 A / D conversion circuit 86 D / A conversion circuit 9 Storage device 100 Optical communication system 110 Optical transmitter 120 Optical receiver 130 Optical fiber 201 Optical amplification unit 202 Demultiplexing unit 203 Conversion Unit 204 monitor unit 205 detection unit 206 storage unit 207 control unit 208 supply unit 300 set value table

Claims (6)

When a communication signal obtained by multiplexing a plurality of optical signals having different wavelengths is input, an optical amplification unit that amplifies and outputs the optical power of the communication signal;
A demultiplexing unit that demultiplexes the communication signal and outputs the plurality of optical signals when the communication signal with the optical power amplified by the optical amplification unit is input;
A monitor unit for measuring the optical power of each of the plurality of optical signals output from the demultiplexing unit;
From the optical power values of the plurality of optical signals measured by the monitor unit, a maximum optical power value, a minimum optical power value, and an optical power difference that is a difference between the maximum optical power value and the minimum optical power value are detected. A detector to
A control unit for controlling the gain of the optical amplification unit,
The optical power difference in a state where the gain of the optical amplification unit is adjusted to the initial value when starting the control is a first target value that is a target value of the maximum optical power value, and the minimum optical power. when greater than a difference between the second target value is a target value of the value the optical power difference threshold, the minimum optical power value to adjust the gain of the optical amplifier unit to the second target value ,
When the optical power difference when the gain of the optical amplification unit is adjusted to the initial value when starting the control is equal to or less than the optical power difference threshold,
If the maximum optical power value is larger than the first target value, the gain of the optical amplification unit is adjusted so that the maximum optical power value becomes the first target value;
If the maximum optical power value is less than or equal to the first target value, the gain of the optical amplification unit is controlled to maintain the initial value state.
The control unit;
An optical receiver comprising: The optical receiver further includes:
A conversion unit that converts the plurality of optical signals output from the demultiplexing unit into electrical signals corresponding to respective optical powers;
The controller is
As the initial value when starting the control, the gain of the optical amplification unit is output from the optical amplifier when an optical signal having the optical power of the minimum reception power of the optical receiver is input to the optical amplifier. the optical receiver according to claim 1, the optical power of the optical signal, characterized in that the size to fit within the dynamic range of the converter unit to be. The optical amplification unit is
The gain changes according to the magnitude of the control current,
The controller is
When adjusting the gain of the optical amplification unit, the optical receiver according to claim 1 or 2, characterized in that to change the size of the control current. The optical receiver further includes:
A conversion unit that converts the plurality of optical signals output from the demultiplexing unit into electrical signals corresponding to respective optical powers;
The monitor unit is
By monitoring the current value of the electrical signal, the optical receiver according to claim 1, characterized by measuring the optical power of the optical signal. When a communication signal obtained by multiplexing a plurality of optical signals having different wavelengths is input, the optical power of the communication signal is amplified,
Demultiplexing the communication signal in which the optical power is amplified;
Measure the optical power of each of the plurality of optical signals demultiplexed by the process of demultiplexing the communication signal,
From the measured optical power values of the plurality of optical signals, the maximum optical power value, the minimum optical power value, and the optical power difference that is the difference between the maximum optical power value and the minimum optical power value,
Control of gain in amplification of optical power of the communication signal,
The optical power difference in a state where the gain is adjusted to the initial value when starting the control is a first target value that is a target value of the maximum optical power value and a target value of the minimum optical power value when greater than the optical power difference threshold, which is the difference between the second target value is the the minimum optical power value to adjust the gain such that the second target value,
When the optical power difference in the state where the gain is adjusted to the initial value when starting the control is equal to or less than the optical power difference threshold,
If the maximum optical power value is greater than the first target value, the gain is adjusted so that the maximum optical power value becomes the first target value ;
If the maximum optical power value is less than or equal to the first target value, the gain is controlled to maintain the initial value state;
An optical receiving method. When a plurality of optical signals of different wavelengths is inputted, the optical transmitter Ru comprising a multiplexing section that outputs a communication signal by multiplexing optical signals of the plurality of,
An optical receiver,
When a communication signal transmitted from the optical transmitter is input, an optical amplification unit that amplifies and outputs the optical power of the communication signal;
A demultiplexing unit that demultiplexes the communication signal and outputs the plurality of optical signals when the communication signal with the optical power amplified by the optical amplification unit is input;
A monitor unit for measuring the optical power of each of the plurality of optical signals output from the demultiplexing unit;
With reference to the optical power values of the plurality of optical signals measured by the monitor unit, a maximum optical power value, a minimum optical power value, and an optical power difference that is a difference between the maximum optical power value and the minimum optical power value; A detection unit for detecting
A control unit for controlling the gain of the optical amplification unit,
The optical power difference in a state where the gain of the optical amplification unit is adjusted to the initial value when starting the control is a first target value that is a target value of the maximum optical power value, and the minimum optical power. when greater than a difference between the second target value is a target value of the value the optical power difference threshold, the minimum optical power value to adjust the gain of the optical amplifier unit to the second target value ,
When the optical power difference when the gain of the optical amplification unit is adjusted to the initial value when starting the control is equal to or less than the optical power difference threshold,
If the maximum optical power value is larger than the first target value, the gain of the optical amplification unit is adjusted so that the maximum optical power value becomes the first target value ;
If the maximum optical power value is less than or equal to the first target value, the gain of the optical amplification unit is controlled to maintain the initial value state.
The control unit;
The optical receiver comprising:
An optical communication system comprising:

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