Optical Receiver and Optical Transceiver Module

Abstract

This application relates to an optical receiver and an optical transceiver module. An optical receiver includes: an optical amplifier that amplifies an optical signal containing a plurality of wavelengths received; a monitoring circuit that monitors the optical intensity of the demultiplexed optical signal; a processor; and a memory having information representing the relationship between the total incident optical intensity of the optical signal incident on the optical amplifier and the gain of the optical amplifier for each wavelength. The processor repeats the following calculations until the total incident optical intensity converges: a first calculation for determining the gain for each wavelength from the memory based on an estimated value of the drive current for driving the optical amplifier and the total incident optical intensity of the optical signal; a second calculation for calculating the incident optical intensity of each wavelength of the optical signal based on the gain and the monitored optical intensity; and a third calculation for calculating the total incident optical intensity of the optical signal.

Description

Technical Field

[0001] This document relates to an optical receiver and an optical transceiver module. Background Art

[0002] One of the technologies for handling the increasing traffic in data communication is optical fiber transmission called wavelength division multiplexing (WDM). WDM can increase the transmission rate of each optical fiber by multiplexing optical signals of multiple wavelengths onto a single optical fiber. Before demultiplexing the WDM signal into individual wavelengths, the receiver-side device amplifies the received WDM signal using a semiconductor optical amplifier (SOA) or other types of amplifiers as needed.

[0003] Figure 1 An optical receiver RX with a built-in SOA used in a WDM communication device is illustrated. The input optical signal (i.e., the received WDM signal) is amplified by the SOA 111 before the WDM signal is demultiplexed into individual wavelengths by an optical demultiplexer 112 (denoted as "O-DEMUX" in the drawings). The gain of the SOA 111 depends not only on the drive current I of the current source 116 used to drive the SOA 111 SOA , but also on the total incident optical intensity incident on the SOA111 (denoted as "P TOTAL " in the drawings). Therefore, a monitoring photodetector (denoted as "mPD" in the drawings) 114 is provided on the incident side of the SOA 111 to detect the total incident optical intensity on the SOA 111. For example, see Patent Document 1 presented below. In addition, a monitoring circuit 151 is provided on the output side of the optical demultiplexer 112 to monitor the optical intensity of the demultiplexed signals of each wavelength (i.e., channel) detected by the associated photodetectors (denoted as "PD" in the drawings) 113.

[0004] The processor 130 refers to the gain table 141 and calculates the SOA gain of each channel based on the total incident optical intensity P of the SOA 111 TOTAL and the drive current I SOA . The processor 130 also calculates the incident optical intensity of each channel incident on the SOA 111 based on the SOA gain of each channel and the monitored optical intensity. The incident optical intensity of each channel is reported to the WDM communication device as input optical information, or used for internal control of the optical receiver RX or some other purpose.

[0005] The above related technical literature is

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-105221. Summary of the Invention

[0007] Technical Problem

[0008] There is a need to reduce the size of a QSFP 100G module for transmission over 40 km, and in particular, there is a need to reduce components and assemblies for obtaining the incident light intensity of WDM channels. However, in the case where there is no tap splitter and monitoring photodetector on the incident side of the SOA, it is difficult to correctly determine the incident light intensity of each channel, which will ultimately hinder the internal control of the optical receiver and / or notification to the communication device including the optical receiver.

[0009] In one aspect of the present invention, there is provided an optical receiver that accurately detects the incident light intensity of each WDM channel or wavelength and the total incident light intensity of the received WDM signal.

[0010] Technical solution

[0011] In one embodiment, an optical receiver includes:

[0012] An optical amplifier that amplifies an optical signal in which multiple wavelengths are multiplexed;

[0013] A current source that drives the optical amplifier;

[0014] An optical demultiplexer that demultiplexes the amplified optical signal into multiple wavelengths;

[0015] An optical detector, each of which detects one of the demultiplexed wavelengths;

[0016] A monitoring circuit that monitors the light intensity of the demultiplexed wavelengths detected by the optical detector;

[0017] A processor; and

[0018] A memory,

[0019] wherein the memory has information representing the relationship between the total incident light intensity of the optical signal incident on the optical amplifier and the gain of the optical amplifier for each of the multiple wavelengths, and

[0020] wherein the processor repeats the following calculations until the total incident light intensity converges:

[0021] A first calculation for determining the gain of each of the multiple wavelengths of the optical signal based on the drive current of the current source and an estimated value of the total incident light intensity of the optical signal incident on the optical amplifier, with reference to the information in the memory,

[0022] A second calculation for calculating the incident light intensity of each of the multiple wavelengths of the optical signal incident on the optical amplifier based on the gain of each of the determined multiple wavelengths and the light intensity of each of the monitored demultiplexed wavelengths obtained from the monitoring circuit, and

[0023] Third calculation: Based on the sum of the incident light intensities of multiple wavelengths obtained through the second calculation, calculate the total incident light intensity of the optical signal incident on the optical amplifier.

[0024] Technical effects

[0025] The optical receiver can accurately detect the incident light intensity of each WDM channel or wavelength, and the total incident light intensity of the received WDM signal. Description of the drawings

[0026] Figure 1 Illustrates a conventional optical receiver with a built-in SOA used in a WDM communication device;

[0027] Figure 2 Is a schematic diagram of an optical transceiver module with an optical receiver according to an embodiment;

[0028] Figure 3 Is a schematic diagram of the optical receiver of this embodiment;

[0029] Figure 4 Is a flowchart of the process executed by the processor of the optical receiver;

[0030] Figure 5 Illustrates an example of a gain table;

[0031] Figure 6 Illustrates the information of channel (ch1) described in the gain table as a characteristic curve;

[0032] Figure 7 Illustrates the experimental results of the error convergence in detecting the incident light intensity through iterative calculation;

[0033] Figure 8 Is a flowchart of the process for calculating the initial value of the total incident light intensity of the optical signal incident on the SOA; and

[0034] Figure 9 Illustrates an example of calculating the initial value for estimating the total incident light intensity of the optical signal incident on the SOA. Detailed implementation manners

[0035] In an embodiment, the channel (or wavelength)-based optical intensity of each WDM signal incident on the SOA and the total optical intensity of the WDM signal are accurately detected without providing a monitoring mechanism on the incident side of the SOA of the optical receiver. Such an optical receiver can be used in an optical transceiver module for transmission over 40 km (even over 80 km). Specifically, the SOA drive current information and the provisional value of the total incident optical intensity of the WDM signal incident on the SOA (which can be abbreviated as the "SOA total incident optical intensity") are used to determine the SOA gain of each channel, where the SOA gain refers to the gain information stored in the memory. Using the determined SOA gain of each channel and the optical intensity monitoring result of the demultiplexed WDM signal, the optical intensity of each channel (which can be called the "channel-based incident optical intensity") and the total optical intensity of the WDM signal incident on the SOA can be estimated. Based on the estimated SOA total incident optical intensity, the SOA gain of each channel is determined again, and the channel-based incident optical intensity and the SOA total incident optical intensity are recalculated. By repeating these steps, the convergence point of the estimate of the total incident optical intensity of the WDM signal incident on the SOA is determined.

[0036] Figure 2 FIG. 4 is a schematic diagram of an optical transceiver module 1 including an optical receiver 5 according to an embodiment. The optical transceiver module 1 is, for example, a 100G transmission module using an intensity modulation scheme such as non-return-to-zero (NRZ). The optical transceiver module 1 is not limited thereto, and it can be a 400G communication module using an orthogonal pulse amplitude modulation (PAM4) scheme.

[0037] The optical receiver 5 has a receiver photonics assembly (ROSA) 10 as a receiver front-end circuit and a limiting / clock data recovery (CDR) circuit 15 as an electronic circuit connected to the output of the ROSA 10. The optical receiver 5 further includes a processor 30, a memory 40, and a control / monitoring circuit 50. The processor 30, the memory 40, and the control / monitoring circuit 50 can be shared with the transmitter assembly of the optical transceiver module 1.

[0038] The ROSA 10 has an SOA 11, an optical demultiplexer 12, optical detectors 13a to 13d, and preamplifiers 14a to 14d (each abbreviated as "PREAMP" in the drawings). Each of the optical detectors 13a to 13d and each of the preamplifiers 14a to 14d are provided for each demultiplexed channel. The ROSA 10 converts the received optical signal of each channel into an electrical signal. The optical detectors 13a to 13d are, for example, PIN photodiodes (marked as "PIN-PD" in the drawings). The photocurrent detected by the optical detectors 13a to 13d is amplified by the corresponding preamplifiers 14a to 14d and output from the ROSA 10 as an analog voltage signal.

[0039] In Figure 2 the construction example, ROSA 10 is a small optical component without a monitoring mechanism on the incident side of SOA 11. The processor 30 repeatedly estimates the incident light intensity of each channel and the total incident light intensity of the received WDM signal using the temporary value of the total incident light intensity of the WDM signal incident on SOA 11 until the estimated value converges. This process will be described in more detail with reference to Figure 3 The information on the incident light intensity of each channel, which has been obtained as a convergence result, can be provided as a module control and monitoring signal to the communication device to which the optical transceiver module 1 is connected, or can be used for internal control of the optical receiver 5 via the control / monitoring circuit 50.

[0040] The analog voltage signal output from ROSA 10 is regenerated into a digital data stream by the limiter / CDR circuit 15, and the clock is reproduced from the digital data string. The digital data stream is output from the optical receiver 5 as a high-speed main electrical signal.

[0041] On the transmitter side of the optical transceiver module 1, the data signals of each channel to be transmitted are input as electrical inputs to the limiter / CDR circuit 25. The output of the limiter / CDR circuit 25 is connected to the input of the laser diode driver (LDD) 24. LDD 24 converts the input digital electrical signal into a driving signal for optical modulation.

[0042] The driving signal output from LDD 24 is provided to the transmitter photon component (TOSA) 20, which is the transmitter front-end circuit. TOSA 20 has LDs 23a to 23d as light sources. The light beams emitted from LDs 23a to 23d are directly modulated by the corresponding driving signals. The modulated optical signals of each channel are multiplexed by an optical multiplexer (labeled "O-Mux" in the drawing) 21 and emitted from the optical transceiver module 1 as a WDM signal.

[0043] Although Figure 2 a 4-channel WDM optical transceiver module 1 is illustrated, the number of channels to be multiplexed is not limited to four. A WDM communication module that can handle as many channels as required (such as 8 channels, 16 channels or more) can be constructed.

[0044] Figure 3 is a schematic diagram of the optical receiver 5. The optical signal received by the optical receiver 5 is amplified by SOA 11. SOA 11 is driven by the drive current supplied from the current source 16. The drive current I for driving SOA 11 SOAIt is reported to the processor 30. The signal light of multiple wavelengths (i.e., channels) included in the WDM signal is amplified by the SOA 11 and demultiplexed by the optical demultiplexer 12. The demultiplexed signal light of each channel is detected by the associated PIN-PD 13 and converted into a voltage signal by the corresponding preamplifier 14. The voltage signal of each channel is regenerated into a digital data stream by the limiter / CDR circuit 15 and output as a high-speed electrical signal.

[0045] A part of the photocurrent detected by each PIN-PD 13 is monitored by the monitoring circuit 51. The monitoring result of the monitoring circuit 51 is provided to the processor 30 as the PD incident light intensity of each channel.

[0046] The processor 30 serves as a first calculator 31 for determining the SOA gain of a single channel, a second calculator 32 for calculating the incident light intensity of each channel of the WDM signal incident on the SOA 11, a third calculator 33 for calculating the total incident light intensity of the WDM signal incident on the SOA 11, and a determination unit 34.

[0047] The first calculator 31 determines the SOA gain of each channel based on the SOA drive current I SOA with reference to the gain table 41. The gain table 41 is stored in the memory 40, and it records the gain characteristics of each channel. To determine the SOA gain of each channel, in addition to the SOA drive current I SOA the total light intensity of the WDM signal incident on the SOA 11 is also required.

[0048] No monitoring mechanism is provided on the incident side of the SOA 11 in the optical receiver 5. Therefore, a temporary value is initially used as the temporary initial value of the total SOA light intensity of the WDM signal incident on the SOA 11. Even if a certain monitoring mechanism is provided on the incident side of the SOA 11 for some purpose, the temporary value of the total SOA incident light intensity can be used without using this pre-SOA monitoring mechanism to determine the channel-based SOA incident light intensity of each channel. The temporary value of the total SOA incident light intensity can be a randomly selected value, a design value for the fiber optic transmission system, an estimated value obtained by calculation, or any other suitable value. The first calculator 31 determines the SOA gain of each channel based on the SOA drive current I SOA and the temporary value of the total SOA incident light intensity, with reference to the gain table 41. The details of the gain table 41 will be described later.

[0049] The second calculator 32 calculates the incident light intensity of each channel of the WDM signal incident on the SOA 11 based on the channel-based PD incident light intensity provided by the monitoring circuit 51 and the SOA gain of each channel provided by the first calculator 31.

[0050] The third calculator 33 calculates the total incident light intensity of the SOA based on the light intensity of each channel calculated by the second calculator 32. The calculated value of the total incident light intensity of the SOA is fed back to the first calculator 31 and is used to re-determine the SOA gain of each channel. The calculations of the first calculator 31, the second calculator 32, and the third calculator 33 are repeated until the total incident light intensity of the SOA converges. For each iterative calculation, the determination unit 34 updates the estimated value of the total incident light intensity of the SOA.

[0051] The third calculator 33 checks the convergence state of the total incident light intensity of the SOA. Once the estimated value of the total incident light intensity of the SOA converges, the third calculator 33 outputs a convergence signal to the determination unit 34. Once receiving the convergence signal from the third calculator 33, the determination unit 34 fixes the estimated value of the incident light intensity of each channel and outputs the fixed value of the incident light intensity of each channel. The incident light intensity of each channel is reported to the communication device to which the optical transceiver module 1 is connected as incident light information (such as a module control / monitoring signal), or they can be used for the internal control of the optical receiver 5 via the control / monitoring circuit 50.

[0052] Figure 4 is a flowchart of a process implemented by the processor 30. The processor 30 obtains the PD incident light intensities PDin_ch1, PDin_ch2, ……, PDin_ch n of each channel from the monitoring circuit 51 (S11). The PD incident light intensity represents the power level of the signal light incident on the PIN-PD13a to PIN-PD13d after being demultiplexed by the optical demultiplexer 12.

[0053] The processor 30 obtains the SOA drive current value I configured in the current source 16 SOA (S12). The processor 30 sets the initial value Pin_total_init as the initial estimated value Pin_total of the total incident light intensity of the WDM signal incident on the SOA 11 (S13). Steps S11 to S13 can be executed in any order or can be executed simultaneously.

[0054] Then, based on the SOA drive current I SOA and the temporary value of the total incident light intensity of the SOA Pin_total (or Pin_total_init in the first round), the SOA gain of a single channel is obtained from the gain table 41 (S14). Each incident light intensity Pin_ch1, Pin_ch2, ……, Pin_ch n is calculated by multiplying the SOA gain of the corresponding channel by the PD incident light intensity of that channel obtained by the monitoring circuit 51 (S15). The signal intensity of each wavelength incident on the SOA 11 is represented by the product of the power level detected by the corresponding PIN-PD13 and the SOA gain of the associated channel.

[0055] Then, calculate the new total incident optical intensity Pin_total_new (S16) of the SOA based on the sum of the incident optical intensities of the respective channels incident on the SOA. If the error between the currently calculated Pin_total_new and the previously configured Pin_total exceeds the acceptable range ("Yes" in S17), then update the estimated value of the total incident optical intensity of the SOA (S18). Then, the process returns to step S14, and steps S14 to S18 are repeated until the error between the currently calculated Pin_total_new and the previously configured Pin_total is within the acceptable range ("No" in S17). This iteration can be referred to as "Iterative Estimation Process A".

[0056] If the error between the currently calculated Pin_total_new and the previously configured Pin_total is within the acceptable range, then output the calculated incident optical intensities Pin_chl, Pin_ch2,..., Pin_ch n of the respective channels of the SOA (S19). As will be described later, the total incident optical intensity of the SOA converges very quickly through iteration and can quickly and accurately estimate the incident optical intensities 11 of the respective channels of the SOA without providing a monitoring mechanism on the incident side of the SOA.

[0057] The process repeatedly executed by the processor 30 in actual service Figure 4 The intensity of the WDM signal received at the optical receiver 5 may vary due to the deterioration of the transmitting-side communication device over time or fluctuations on the optical fiber transmission line. Despite such deterioration or fluctuations in the WDM signal intensity, in the optical receiver 5 of the present embodiment, the incident optical intensities of the respective channels of the WDM signal incident on the SOA 11 are correctly detected even without a monitoring mechanism at the incident side of the SOA 11. Therefore, the control and monitoring operations of the optical receiver 5 are reliably maintained.

[0058] Figure 5 An example of the gain table 41 stored in the memory 40 is illustrated. Assuming a 4-channel WDM signal, in this example, gain tables 41-1 to 41-4 are provided corresponding to channels Ch1 to Ch4.

[0059] For each channel, the SOA gain (dB) is recorded, and each SOA gain is specified by the SOA drive current I SOA (mA) and the total incident optical intensity (dBm) of the WDM signal incident on the SOA 11. For each channel, the values of the recorded SOA gains are measured in advance, and each SOA gain value is determined by the drive current I SOA (mA) of the SOA 11 and the total incident optical intensity Pin_total (dBm) of the SOA.

[0060] Figure 6 illustrates an information item in the gain table 41-1 of channel Ch1 recorded in, for example, Figure 5 which is illustrated as characteristic chart 41-1a in Figure 6 The horizontal axis represents the SOA total incident light intensity Pin_total, and the vertical axis represents the SOA gain. The SOA gain is defined as a function of the SOA total incident light intensity for each of eight values of the SOA drive current I SOA ranging from 20 mA to 180 mA.

[0061] The first calculator 31 of the processor 30 determines the SOA gain of each channel with reference to the gain tables 41-1 to 41-4 based on the SOA drive current I SOA configured in the current source 16 and the SOA total incident light intensity temporarily configured as an initial value or recalculated during the iterative estimation process. The second calculator 32 calculates the channel-based SOA incident light intensity based on the SOA gain of each channel and the monitoring results of the PIN-PD 13a to 13d.

[0062] The third calculator 33 calculates a new SOA total incident light intensity Pin_total_new based on the sum of the SOA incident light intensities of each channel.

[0063] The calculations performed by the processor 30 are represented by the following formula.

[0064] Pin_ch n = (PIW_PD_in n ÷ LOSS n ) ÷ G n

[0065]

[0066] where Pin_ch n represents the SOA incident light intensity of a single channel.

[0067] The channel-based SOA incident light intensity Pin_ch n multiplied by the SOA gain and the optical loss of the channel gives the PD incident light intensity, which represents the intensity of the signal light incident on the associated PIN PD after demultiplexing. "LOSSn" represents the optical loss at channel "n" caused by the optical demultiplexer 12. The channel-based SOA incident light intensity Pin_ch n is expressed as the quotient obtained by dividing the PD incident light intensity PDin_ch n by the optical loss "LOSSn" caused by the optical demultiplexer 12 and dividing by the SOA gain "Gn" of the channel. Based on the SOA drive current I SOAAnd the total incident light intensity of the temporary SOA, the SOA gain "Gn" of each channel is obtained from the gain tables 41-1 to 41-4. By summing up the channel-based SOA incident light intensity Pin_ch n of each channel, a new total incident light intensity of the SOA Pin_total_new is obtained.

[0068] Using a simple formula, the total incident light intensity of the SOA is repeatedly calculated until the new total incident light intensity of the SOA Pin_total_new converges.

[0069] Figure 7 The experimental results of the detection error of the incident light intensity of a certain channel converging through the above iteration are illustrated. The convergence state is calculated by changing the error before operation within the range of ±20 dB. Through four or more iterations of calculation, the error converges to less than 0.5 dB, as shown in the circular area B in the attached figure. If the error between the initial set value (i.e., the temporary value) of the total incident light intensity of the SOA and the true value is within ±3 dB, the error converges to less than 0.5 dB only through 3 iterations.

[0070] From Figure 7 the results, it can be understood that even if the initially selected temporary value of the total incident light intensity of the SOA is significantly different from the actual value, the total incident light intensity of the SOA quickly and accurately converges to the expected value through four or more iterations of calculation. According to the system design, the number of iterations can be limited to a predetermined number, for example, 3 times. In this case, due to faster convergence, it is preferable to select an initial value with a smaller error.

[0071] Figure 8 is a flowchart of a calculation example of the initial value of the total incident light intensity of the temporary SOA. Based on the SOA drive current I SOA 、gain table 41 and the PD incident light intensities of PIN-PD 13a to 13d, the initial value of the total incident light intensity of the SOA can be narrowed down to a closer value to some extent. For example, by using the median or average value between the maximum possible error and the minimum possible error, the temporary value of the total incident light intensity of the SOA can be made closer to the actual total incident light intensity of the SOA to some extent.

[0072] First, for the optical intensity PDin_ch n of each wavelength that is amplified, demultiplexed, and input to the associated PIN-PD 13n by the SOA 11, a minimum value Pin_chn_min (S131) is determined from the possible range of the incident optical intensity Pin_ch n of the channel-based SOA. Similarly, for the optical intensity PDin_ch n of each wavelength incident on the associated PIN-PD 13n, a maximum value Pin_ch n_max (S132) is determined from the possible range of the incident optical intensity Pin_ch n of the channel-based SOA. Steps S131 and S132 can be executed in any order or can be executed simultaneously.

[0073] Calculate the average of the sum of the minimum values Pin_ch n_min of all channels and the sum of the maximum values Pin_ch n_max of all channels, and determine it as the initial value of the total incident optical intensity of the SOA (S133).

[0074] Figure 9 An example calculation of the initial value of the total incident optical intensity of the SOA is illustrated. The horizontal axis represents the incident optical intensity Pin_ch of each channel incident on the SOA, and the vertical axis represents the incident optical intensity PD_in n incident on the associated PIN-PD 13n.

[0075] The solid line (1) represents the characteristics of the case where all channels have the same optical intensity. The dashed line (2) represents the characteristics of the case where the total incident optical intensity of the SOA is the same as in case (1), but a certain channel has the minimum value of the incident optical intensity Pin_ch n on the SOA 11. The dotted line (3) represents the characteristics of the case where the total incident optical intensity of the SOA is the same as in case (1), but a certain channel has the maximum value of the incident optical intensity Pin_ch n on the SOA 11. These characteristics of lines (1) to (3) are measured in advance and stored in the memory 40.

[0076] The intersection of the line (1) and the horizontal dashed line at X (dBm) of PD_in n represents the incident optical intensity of the SOA for each channel when all channels have the same optical intensity. The intersection of the line (2) and the horizontal dashed line at X (dBm) of PD_in n represents the minimum value that the incident optical intensity Pin_ch n of the channel-based SOA can take when PD_inn is X (dBm).

[0077] The intersection of the line (3) and the horizontal dashed line at X (dBm) of PD_in n represents the maximum value that the incident optical intensity Pin_ch n of the channel-based SOA can take when PD_in n is X (dBm).

[0078] The minimum value Pin_ch n_min of the SOA incident light intensity based on the channel can be determined by, for example, the following formula.

[0079]

[0080] The channel-based PD incident light intensity incident on the associated PIN-PD 13n is obtained by multiplying the minimum value Pin_ch n_min of the SOA incident light intensity of the corresponding channel by the associated SOA gain Gn. That is, Figure 9 The line (2) in Figure 9 represents the characteristic of the SOA gain Gn that minimizes Pin_ch n.

[0081] The minimum value Pin_ch n_min of the SOA incident light intensity based on the channel is obtained by dividing the total SOA incident light intensity Pin_total by "divl". In the case of 4 channels, div1 is expressed as That is, 4 × 10 Δp / 10 , where Δp is Figure 9 the difference between line (1) and line (2) at X (dBm) of PD_in n in Figure 9 . Only Δp is in [dB] (logarithmic) units, and the rest are in antilogarithmic form.

[0082] The maximum value Pin_ch n_max of the SOA incident light intensity based on the channel can be obtained by, for example, the following formula.

[0083]

[0084] The channel-based PD incident light intensity incident on the corresponding PIN-PD 13n is obtained by multiplying the maximum value Pin_ch n_max of the SOA incident light intensity of the corresponding channel by the associated SOA gain Gn. That is, Figure 9 The line (3) in Figure 9 represents the characteristic of the SOA gain Gn that maximizes Pin_ch n.

[0085] The maximum value Pin_ch n_max of the SOA incident light intensity based on the channel is obtained by dividing the total SOA incident light intensity Pin_total by "div2". In the case of 4 channels, div2 is expressed as That is, 4 × 10 Δm / 10 , where Δm is Figure 9 the difference between line (1) and line (3) at X (dBm) of PD_in n in Figure 9 . Only Δm is in [dB] (logarithmic) units, and the rest are in antilogarithmic form.

[0086] By storing in the memory 40 Figure 9The characteristics of the three lines (1) to (3) therein (i.e., three types of gain characteristics or tables), and by retrieving the position that satisfies the calculation formula of Pin_ch n_min, the minimum value of Pin_ch n_min of the SOA incident light intensity of each channel can be easily determined.

[0087] By searching for the position that satisfies the calculation formula of Pin_ch n_max in the three gain tables, the maximum value Pin_ch n_max of the SOA incident light intensity of each channel can be easily determined.

[0088] The initial value Pin_total_init of the total incident light intensity of the SOA can be calculated by the following formula.

[0089] Pin_total_init = 10 {∑10·log(Pin_chn_min)+∑10·log(Pin_chn_max)} / 2 / 10

[0090] The meaning of this arithmetic expression is to determine the average value of the sum of Pin_ch n_min and the sum of Pin_ch n_max of all channels in logarithmic form, and then convert the average value to an antilogarithm. This is because if the average value of the sum of Pin_ch n_min and the sum of Pin_ch n_max of all channels is calculated in antilogarithm, the average value may be skewed towards the Pin_ch n_max side.

[0091] By storing in the memory 40 Figure 9 the three types of characteristics (gain tables), in the case of a limited number of iterations, the initial value of the total incident light intensity of the SOA can be easily calculated. The calculated initial value can be used as a temporary value of the total incident light intensity of the SOA for starting the iteration.

[0092] According to the above process, without directly measuring the incident light intensity of the WDM signal incident on the SOA, the incident light intensity of each channel of the WDM signal incident on the SOA 11 can be accurately estimated through iteration. Using the above structure, the number of components or assemblies of the optical receiver 5 can be reduced, and the module can be made compact while expanding the dynamic range of the incident light.

[0093] Although the present disclosure has been described based on specific configuration examples, the present disclosure is not limited to the above examples. In the case of a limited number of iterations, the initial value of the temporary total incident light intensity of the SOA can be determined by calculating the average of Pin_ch n_min and Pin_ch n_max for each channel and then calculating the average or median of all channels, rather than calculating the average of the sum of Pin_ch n_min and the sum of Pin_ch n_max for all channels. If there is no limit on the number of iterations, then due to the fast convergence of the process, any value can be randomly selected for the initial value of the total incident light intensity of the SOA.

Claims

1. An optical receiver, the optical receiver comprising: An optical amplifier that amplifies an optical signal in which a plurality of wavelengths are multiplexed; A current source that drives the optical amplifier; An optical demultiplexer that demultiplexes the amplified optical signal into the plurality of wavelengths; An optical detector, each of which detects one of the demultiplexed wavelengths; A monitoring circuit that monitors the optical intensity of the demultiplexed wavelength detected by the optical detector; A processor; And A memory, wherein the memory has information representing the relationship between the total incident optical intensity of the optical signal incident on the optical amplifier and the gain of the optical amplifier for each of the plurality of wavelengths, and wherein the processor repeats the following calculations until the total incident optical intensity converges: A first calculation for determining the gain of each of the plurality of wavelengths of the optical signal based on the drive current of the current source and an estimated value of the total incident optical intensity of the optical signal incident on the optical amplifier, with reference to the information in the memory, A second calculation for calculating the incident optical intensity of each of the plurality of wavelengths of the optical signal incident on the optical amplifier based on the determined gain of each of the plurality of wavelengths and the monitored optical intensity of each of the demultiplexed wavelengths obtained from the monitoring circuit, and A third calculation for calculating the total incident optical intensity of the optical signal incident on the optical amplifier based on the sum of the incident optical intensities of the plurality of wavelengths obtained by the second calculation.

2. The optical receiver according to claim 1, Among them, At the start of the repetition of the first calculation, the second calculation, and the third calculation, the processor uses a temporary value of the total incident optical intensity of the optical signal.

3. The optical receiver according to claim 1, Among them, The processor calculates an initial estimated value of the total incident optical intensity of the optical signal based on the drive current, the information stored in the memory, and the monitored optical intensity obtained from the monitoring circuit.

4. The optical receiver according to claim 3, Among them, The processor calculates the average or median of the sum of the possible maximum values and the sum of the possible minimum values of the incident optical intensities of the plurality of wavelengths of the optical signal incident on the optical amplifier as the initial estimated value of the total incident optical intensity of the optical signal.

5. The optical receiver according to claim 1, Among them, When the total incident optical intensity converges, the processor outputs the incident optical intensities of the plurality of wavelengths of the optical signal incident on the optical amplifier.

6. The optical receiver according to claim 5, the optical receiver further comprising: A control and monitoring circuit that performs internal control of the optical receiver using the incident optical intensities of the plurality of wavelengths of the optical signal incident on the optical amplifier.

7. An optical transceiver module, the optical transceiver module comprising: An optical receiver; And An optical transmitter that converts an electrical signal into an optical signal, Among them, the optical receiver includes: an optical amplifier that amplifies an optical signal in which multiple wavelengths are multiplexed; a current source that drives the optical amplifier; an optical demultiplexer that demultiplexes the amplified optical signal into the multiple wavelengths; an optical detector, each of which detects one of the demultiplexed wavelengths; a monitoring circuit that monitors the optical intensity of the demultiplexed wavelength detected by the optical detector; a processor; and a memory, wherein the memory has information representing the relationship between the total incident optical intensity of the optical signal incident on the optical amplifier and the gain of the optical amplifier for each of the multiple wavelengths, and wherein the processor repeats the following calculations until the total incident optical intensity converges: A first calculation for determining the gain of each of the multiple wavelengths of the optical signal with reference to the information in the memory based on the drive current of the current source and an estimated value of the total incident optical intensity of the optical signal incident on the optical amplifier, A second calculation for calculating the incident optical intensity of each of the multiple wavelengths of the optical signal incident on the optical amplifier based on the gain of each of the determined multiple wavelengths and the monitored optical intensity of each of the demultiplexed wavelengths obtained from the monitoring circuit, and A third calculation for calculating the total incident optical intensity of the optical signal incident on the optical amplifier based on the sum of the incident optical intensities of the multiple wavelengths obtained by the second calculation.

8. The optical transceiver module according to claim 7, Among them, At the start of the repetition of the first calculation, the second calculation, and the third calculation, the processor uses a temporary value of the total incident optical intensity of the optical signal.

9. The optical transceiver module according to claim 7, Among them, The processor calculates an initial estimated value of the total incident optical intensity of the optical signal based on the drive current, the information stored in the memory, and the monitored optical intensity obtained from the monitoring circuit.

10. The optical transceiver module according to claim 9, Among them, The processor calculates the average or median of the sum of the possible maximum values and the sum of the possible minimum values of the incident optical intensities of the multiple wavelengths of the optical signal incident on the optical amplifier as the initial estimated value of the total incident optical intensity of the optical signal.

11. The optical transceiver module according to claim 7, Among them, When the total incident optical intensity converges, the processor outputs the incident optical intensities of the multiple wavelengths of the optical signal incident on the optical amplifier.

12. The optical transceiver module according to claim 11, wherein, The optical receiver has a control and monitoring circuit that performs internal control of the optical receiver using the incident optical intensities of the multiple wavelengths of the optical signal incident on the optical amplifier.

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