Estimation device and estimation method

Abstract

An estimation device 13 includes: a measurement unit 131 for measuring, for an optical transmitter and an optical receiver connected via a transmission path, a signal quality value for each received optical power in the optical receiver; a first calculation unit 132 for calculating a first signal distortion by the optical transmitter and the optical receiver dependent on the received optical power and a second signal distortion by the optical transmitter and the optical receiver independent of the received optical power by using the signal quality measurement value for each received optical power in the optical receiver; and a second calculation unit 133 for calculating a signal quality value for each optical noise amount by using the first signal distortion, the second signal distortion, and a third signal distortion by the transmission path calculated from the optical noise amount so as to calculate a relationship between the signal quality and the transmission quality of the optical transmitter and the optical receiver.

Description

Estimation device and estimation method

[0001] The present disclosure relates to an estimation device and an estimation method.

[0002] Estimating signal quality (e.g., Q-factor, Pre-FEC BER) and measuring transmission quality (e.g., GSNR) are essential technologies for designing, operating, and monitoring optical networks. To estimate signal quality and measure transmission quality with high accuracy, it is necessary to grasp the BER-OSNR characteristics of optical transceivers in a back-to-back configuration in which the optical transmitter and receiver are directly connected by optical fiber with a very short propagation distance.

[0003] For example, in a back-to-back configuration, the optical signal from the optical transmitter and the optical noise from the optical noise generator are multiplexed by a multiplexer, and the optical noise level (OSNR) and signal quality (e.g., Pre-FEC BER) are measured when the multiplexed light is input to an optical receiver. If the measured values ​​are plotted on a graph with the optical noise level (transmission quality) on the horizontal axis and the signal quality on the vertical axis, the BER-OSNR characteristic is obtained, where the signal quality decreases as the optical noise level increases.

[0004] By utilizing this BER-OSNR characteristic, the signal quality of the received signal can be estimated from transmission quality measured or estimated in advance or calculated using a tool such as GNPy (see Non-Patent Document 1). Simply read the signal quality value corresponding to the calculated transmission quality value. Conversely, the transmission quality can be estimated from the signal quality measured by the optical transceiver (see Non-Patent Document 2). Simply read the transmission quality (optical noise amount) value corresponding to the measured signal quality value.

[0005] Vittorio Curri, “GNPy model of the physical layer for open and disaggregated optical networking [Invited]”, JOURNAL OF Optical Communications and Networking, Vol. 14, No. 6, June 2022, C92-C104Kaida Kaeval, and 8 others, “QoT assessment of the optical spectrum as a service in disaggregated network scenarios”, JOURNAL OF Optical Communications and Networking Networking, Vol.13, No.10, October 2021, E1-E12

[0006] However, conventional methods for measuring BER-OSNR characteristics require a large number of optical instruments, including an optical transmitter and an optical receiver, an optical amplifier that amplifies the optical signal from the optical transmitter, a variable optical attenuator that variably attenuates the amplified optical signal, an optical noise generator that generates optical noise, an optical amplifier that amplifies the optical noise, a variable optical attenuator that variably attenuates the amplified optical noise, a multiplexer that combines the amplified and variably attenuated optical signal with the amplified and variably attenuated optical noise, an optical bandpass filter that passes only the desired light from the combined light, a demultiplexer that separates the desired light into an optical receiver and an optical spectrum analyzer, and an optical spectrum analyzer that analyzes the separated light, to measure the signal quality value for each amount of optical noise, which is costly and time-consuming.

[0007] The present disclosure has been made in consideration of the above circumstances, and an object of the present disclosure is to provide a technology that can estimate the relationship between the signal quality and transmission quality of an optical transceiver at low cost.

[0008] An estimation device according to one aspect of the present disclosure includes a measurement unit that measures a signal quality value for each received optical power at an optical receiver for an optical transmitter and an optical receiver connected via a transmission path; a first calculation unit that calculates a first signal distortion caused by the optical transmitter and the optical receiver that depends on the received optical power and a second signal distortion caused by the optical transmitter and the optical receiver that does not depend on the received optical power using the measured value of the signal quality for each received optical power at the optical receiver; and a second calculation unit that calculates the relationship between the signal quality and transmission quality of the optical transmitter and the optical receiver by calculating a signal quality value for each optical noise amount using the first signal distortion, the second signal distortion, and a third signal distortion caused by the transmission path that is calculated from an optical noise amount.

[0009] An estimation method according to one aspect of the present disclosure is an estimation method performed by an estimation device, which includes measuring a signal quality value for each received optical power at an optical receiver for an optical transmitter and an optical receiver connected via a transmission path, calculating a first signal distortion caused by the optical transmitter and the optical receiver that depends on the received optical power and a second signal distortion caused by the optical transmitter and the optical receiver that does not depend on the received optical power using the measured value of signal quality for each received optical power at the optical receiver, and calculating a signal quality value for each optical noise amount using the first signal distortion, the second signal distortion, and a third signal distortion caused by the transmission path calculated from the optical noise amount, thereby calculating a relationship between the signal quality and transmission quality of the optical transmitter and the optical receiver.

[0010] According to the present disclosure, it is possible to provide a technology that can estimate the relationship between the signal quality and transmission quality of an optical transceiver at low cost.

[0011] Fig. 1 is a diagram showing an example of the configuration of an estimation system according to this embodiment. Fig. 2 is a diagram showing another example of the configuration of a transmission system. Fig. 3 is a diagram showing measurement results of signal quality values ​​for each received optical power. Fig. 4 is a diagram showing comparison results between estimated values ​​and actual measured values ​​of BER-OSNR characteristics. Fig. 5 is a flow chart showing a method for calculating BER-OSNR characteristics. Fig. 6 is a diagram showing an example of the hardware configuration of an estimation device.

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the description of the drawings, the same parts are designated by the same reference numerals and the description thereof will be omitted.

[0013] [Summary of the Disclosure] The disclosure discloses a method for estimating the BER-OSNR characteristics of an optical transceiver by using a computer without using optical devices such as an optical amplifier, a variable optical attenuator, an optical noise generator, a multiplexer, an optical bandpass filter, a demultiplexer, an optical spectrum analyzer, etc. However, the use of an optical attenuator is not excluded.

[0014] Specifically, (a) the signal quality value (change in the signal quality value) is measured and recorded while changing the received optical power at the optical receiver, and from the results, (a1) signal distortion caused by the optical transceiver that depends on the received optical power, and (a2) signal distortion caused by the optical transceiver that does not depend on the received optical power are calculated.

[0015] Furthermore, (b) the BER-OSNR characteristics of the optical transceiver are estimated by calculating the signal quality (e.g., Q factor, Pre-FEC BER) for each optical noise level using the above two signal distortions caused by the optical transceiver and the signal distortion caused by the transmission path calculated from the optical noise level (OSNR).

[0016] This allows the relationship between the signal quality and transmission quality of an optical transceiver to be estimated at low cost.

[0017] 1 is a diagram showing an example of the configuration of an estimation system 1 according to this embodiment. The estimation system 1 includes a transmission system including an optical transmitter 11, an optical receiver 12, and an estimation device 13.

[0018] The optical transmitter 11 is a device that transmits an optical signal to the optical receiver 12. The optical receiver 12 is a device that receives the optical signal from the optical transmitter 11. The optical transmitter 11 and the optical receiver 12 have a back-to-back configuration in which they are connected by an optical fiber (transmission path) 14 with a very short propagation distance.

[0019] The estimation device 13 is connected to each of the transmission system and the optical receiver 12, and is a device that estimates the BER-OSNR characteristics of the optical transceivers (11, 12) (the relationship between the signal quality and transmission quality of the optical transceivers (11, 12)).

[0020] The estimation device 13 includes a measurement unit 131 , a first calculation unit 132 , and a second calculation unit 133 .

[0021] The measurement unit 131 has the function of measuring and recording the signal quality value (change in the signal quality value) for each received optical power at the optical receiver 12 while changing the received optical power at the optical receiver 12 by adjusting the output optical power from the transmission system.

[0022] The output optical power from the transmission system is approximately equivalent to the received optical power at the optical receiver 12, and adjusting the output optical power at the transmission system also changes the received optical power at the optical receiver 12. For example, the measurement unit 131 measures and records the signal quality while changing the received optical power at the optical receiver 12 by adjusting the output optical power at the optical transmitter 11.

[0023] 2, a variable attenuator 15 or a plurality of attenuators (not shown) with different fixed values ​​may be connected between the optical transmitter 11 and the optical receiver 12, and the output optical power may be adjusted by the variable attenuator 15 or the plurality of attenuators to change the received optical power at the optical receiver 12. The transmission system may be configured to be capable of varying the received optical power at the optical receiver 12.

[0024] In order to realize this function, the measurement unit 131 includes, as shown in FIG. 1, an equipment control unit 131a that sets the optical transceivers (11, 12) to transmit and receive optical signals, an output optical power control unit 131b that adjusts the output optical power of the optical signal output from the optical transmitter 11 in the transmission system in order to change the received optical power at the optical receiver 12, a received optical power measurement unit 131c that measures and records the received optical power of the optical signal input to the optical receiver 12, and a signal quality measurement unit 131d that measures the signal quality value of the optical signal received by the optical receiver 12 and records it in association with the received optical power at the time of measurement.

[0025] The first calculation unit 132 has a function of calculating signal distortion (first signal distortion) caused by the optical transceiver (11, 12) that depends on the received optical power and signal distortion (second signal distortion) caused by the optical transceiver (11, 12) that does not depend on the received optical power, using the measurement value of the signal quality for each received optical power measured by the measurement unit 131.

[0026] For example, the first calculation unit 132 calculates the first signal distortion and the second signal distortion so that the measured value of the signal quality for each received optical power matches the calculated value of the signal quality calculated from the sum of the first signal distortion and the second signal distortion multiplied by the received optical power.

[0027] The second calculation unit 133 has a function of estimating and calculating the BER-OSNR characteristics of the optical transceivers (11, 12) by calculating a signal quality value (e.g., Q factor, Pre-FEC BER) for each amount of optical noise using the two signal distortions (first signal distortion and second signal distortion) caused by the optical transceivers (11, 12) calculated by the first calculation unit 132 and the signal distortion (third signal distortion) caused by the optical fiber 14 calculated from the amount of optical noise (OSNR).

[0028] For example, the second calculation unit 133 calculates the signal distortion caused by the optical transceiver (11, 12) when the received optical power is a predetermined value based on the calculation results of the first signal distortion and the second signal distortion. Thereafter, the second calculation unit 133 further calculates a third signal distortion corresponding to each optical noise amount, and calculates the signal quality value for each optical noise amount by combining these two calculation results, thereby calculating the BER-OSNR characteristics of the optical transceiver (11, 12).

[0029] Specifically, for example, the second calculation unit 133 calculates the BER-OSNR characteristics of the optical transceiver (11, 12) by calculating the signal quality value for each amount of optical noise for a specified received optical power using a formula for calculating the signal quality value from the sum of the first signal distortion, the second signal distortion, and the third signal distortion multiplied by the received optical power.

[0030] [Method of Calculating Signal Distortion Caused by Optical Transmitter / Receiver] A method of calculating signal distortion caused by the optical transmitter / receiver (11, 12) performed by the first calculation unit 132 will be described.

[0031] In this embodiment, an existing BER-OSNR model that does not take into account signal distortion due to changes in received optical power is extended so that signal distortion due to changes in received optical power can be taken into account.

[0032] The existing BER-OSNR model is expressed by equation (1).

[0033]

[0034] Equation (1) is described in "Toru Mano et al., "Modeling Transceiver BER-OSNR Characteristic for QoT Estimation in Short-Reach Systems," 2023 International Conference on Optical Network Design and Modeling (ONDM) (ONDM 2023), Coimbra, Portugal."

[0035] Ψ is a function determined by the signal modulation method. In the case of DP-16QAM, Ψ (SNR) = (3 / 8)erfc (√(SNR / 10)). SNR TRX is the SNR of the noise generated in the optical transceiver (11, 12). ASE is the SNR of ASE noise generated by optical noise generators and optical amplifiers (ASE), and is obtained by converting OSNR to SNR. NLI is the SNR of NLI noise generated by fiber nonlinear effects such as WDM.

[0036] Δf is the noise measurement bandwidth in OSNR measurement. Typically, Δf = 12.5 GHz. R is the signal bandwidth. For 400G DP-16QAM standardized by OpenROADM, R is approximately 63.1 GHz. ξ is a constant greater than or equal to 1 that represents the imperfection of the optical receiver filter.

[0037] In the back-to-back configuration, there is no wavelength multiplexing and the propagation distance of the optical fiber 14 is very short, so the influence of the fiber nonlinear optical effect can be ignored. NLI is excluded from consideration.

[0038] To consider signal distortion due to the received optical power, the received optical power is set as P in Then, the existing BER-OSNR model shown in equation (1) is extended as shown in equation (2).

[0039]

[0040] SNR TRX-inis the received optical power P from the noise generated in the optical transceiver (11, 12). in This SNR is the SNR excluding noise related to TRX-in is the received optical power P in This corresponds to signal distortion (second signal distortion) caused by the optical transceivers (11, 12) that does not depend on the signal distortion.

[0041] SNR in P in is the received optical power P in is the SNR of the noise related to this SNR in is the received optical power P in This corresponds to the signal distortion (first signal distortion) caused by the optical transceiver (11, 12) that depends on the received optical power P in When becomes smaller, the SNR in P in The signal quality will be degraded.

[0042] From equation (2), the received optical power P in The relationship between the signal quality (BER) and the BER can be expressed as in equation (3).

[0043]

[0044] The back-to-back configuration shown in Figure 1 does not include an optical noise generator or an optical amplifier (ASE), so the SNR corresponding to the ASE noise from the optical noise generator is ASE was excluded.

[0045] From equation (3), the signal quality value (BER) is calculated by the received optical power P in and the received optical power P in The signal distortion parameter (SNR) due to the optical transceiver (11, 12) is independent of TRX-in ) and the received optical power P in The parameter of signal distortion (SNR) due to the optical transceiver (11, 12) depends on in ) and is determined by.

[0046] Therefore, the first calculation unit 132 calculates the received optical power P inThe two parameters (SNR) are calculated using the least squares method or the like so that the measured signal quality (BER) for each channel matches the calculated signal quality (BER) calculated by Equation (3). TRX-in , SNR in ) is calculated.

[0047] FIG. 3 shows the received optical power P in The horizontal axis shows the measurement results of the signal quality value (BER) for each received optical power P in The vertical axis is the signal quality value (Q value). The Q value and BER have a one-to-one relationship, BER=(1 / 2)erfc(Q / √(2)). By parameter fitting using the least squares method, the two parameters (SNR TRX-in , SNR in ) can be calculated.

[0048] [Method of Calculating BER-OSNR Characteristics] A method of calculating the BER-OSNR characteristics performed by the second calculation unit 133 will be described.

[0049] To estimate the BER-OSNR characteristics, the extended BER-OSNR model of Equation (2) is used. The two parameters (SNR TRX-in , SNR in ) into equation (2) to calculate the BER-OSNR characteristics. ASE corresponds to the signal distortion (third signal distortion) caused by the optical fiber 14 calculated from the optical signal noise ratio (OSNR).

[0050] Received optical power P in We will explain how to calculate the BER-OSNR characteristics when p.

[0051] To estimate the BER-OSNR characteristics, the second calculation unit 133 calculates the signal quality (BER) for each OSNR. From the extended BER-OSNR model of Equation (2), the received optical power P in The signal quality value (BER) when p is the signal quality parameter and r is the OSNR is calculated by the first calculation unit 132 using the two parameters (SNR TRX-in , SNR in ), it can be expressed as in equation (4).

[0052]

[0053] To explain again, the left side is SNR -1 In the formula, SNR TRX-in is the received optical power P in A parameter of signal distortion (second signal distortion) caused by the optical transceiver (11, 12) that does not depend on SNR in is the received optical power P in a parameter (first signal distortion) of the signal distortion caused by the optical transceiver (11, 12) that depends on SNR ASE is a parameter of signal distortion (third signal distortion) caused by the optical fiber 14 calculated from the OSNR.

[0054] By using equation (4), the signal quality (BER) for each OSNR can be calculated, and the BER-OSNR characteristics can be estimated.

[0055] 4 is a diagram showing the comparison results between the BER-OSNR characteristics (solid line) estimated by the second calculation unit 133 and the actually measured BER-OSNR characteristics (x symbols). The vertical axis represents the Q factor. It can be seen that the estimated values ​​and the actually measured values ​​match well with each other.

[0056] (Another Calculation Method) The BER-OSNR characteristics can also be calculated using the following calculation method.

[0057] First, the second calculation unit 133 calculates the two parameters (SNR TRX-in , SNR in ) into equation (3) to obtain the received optical power P in The signal distortion (SNR) caused by the optical transceiver (11, 12) when p is calculated is expressed as SNR in Equation (2). TRX This becomes:

[0058] Thereafter, the second calculation unit 133 calculates the signal distortion (SNR) due to the optical fiber 14 corresponding to each OSNR (=r) using the fourth line of equation (2). ASE ) and calculate the signal distortion (SNR ASE ) and the signal distortion (SNR (=SNR TRX )) to estimate and calculate the signal quality (BER) for each OSNR.

[0059] [Operation of Estimation Device] FIG. 5 is a flowchart showing a method for calculating BER-OSNR characteristics performed by the estimation device 13. As shown in FIG.

[0060] Step S1: The measurement unit 131 measures the received optical power P in Measure and record the signal quality value (BER) for each signal.

[0061] Step S2: Next, the first calculation unit 132 calculates the received optical power P in The received optical power P is calculated using the least squares method or the like so that the measured signal quality (BER) for each signal matches the calculated signal quality (BER) calculated by equation (3). in The signal distortion parameter (SNR) due to the optical transceiver (11, 12) is independent of TRX-in ) and the received optical power P in The parameter of signal distortion (SNR) due to the optical transceiver (11, 12) depends on in ) and calculate.

[0062] Step S3: Finally, the second calculation unit 133 calculates the two parameters (SNR TRX-in , SNR in ) into the extended BER-OSNR model in equation (2), and obtain the desired received optical power P in The BER-OSNR characteristics are estimated by calculating the signal quality (BER) for each OSNR.

[0063] [Effect] According to the present embodiment, the estimation device 13 includes a measurement unit 131 that measures a value of signal quality for each received optical power at the optical receiver 12 for the optical transmitter 11 and the optical receiver 12 that are connected via an optical fiber 14; a first calculation unit 132 that calculates, using the measured value of signal quality for each received optical power at the optical receiver 12, a signal distortion (first signal distortion) caused by the optical transceivers (11, 12) that depends on the received optical power and a signal distortion (second signal distortion) caused by the optical transceivers (11, 12) that does not depend on the received optical power; and a second calculation unit 133 that calculates a BER-OSNR characteristic of the optical transceivers (11, 12) by calculating a value of signal quality for each optical noise amount (e.g., Q factor, Pre-FEC BER) using the signal distortion (third signal distortion) caused by the optical fiber 14 that is calculated from the first signal distortion, the second signal distortion, and the optical noise amount (OSNR). This makes it possible to estimate the BER-OSNR characteristic of the optical transceivers (11, 12) at low cost.

[0064] Furthermore, according to this embodiment, the BER-OSNR characteristics of the optical transceivers (11, 12) are calculated by the computer-based estimation device 13 without using optical equipment such as an optical amplifier, a variable optical attenuator, an optical noise generator, a multiplexer, an optical bandpass filter, a demultiplexer, or an optical spectrum analyzer, so that signal quality can be estimated and transmission quality can be calculated at low cost.

[0065] [Others] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present disclosure.

[0066] The estimation device 13 of the present embodiment described above can be realized, for example, by using a general-purpose computer system including a CPU 901, a memory 902, a storage 903, a communication device 904, an input device 905, and an output device 906, as shown in Fig. 6. The memory 902 and the storage 903 are storage devices. In the computer system, the CPU 901 executes a predetermined program loaded onto the memory 902, thereby realizing each function of the estimation device 13.

[0067] The estimation device 13 may be implemented by one computer. The estimation device 13 may be implemented by multiple computers. The estimation device 13 may be a virtual machine implemented on a computer.

[0068] The program for the estimation device 13 can be stored in a computer-readable recording medium such as a HDD, SSD, USB memory, CD, or DVD. The computer-readable recording medium is, for example, a non-transitory recording medium. The program for the estimation device 13 can also be distributed via a communication network.

[0069] REFERENCE SIGNS LIST 1 Estimation system 11 Optical transmitter 12 Optical receiver 13 Estimation device 14 Optical fiber 15 Variable attenuator 131 Measurement unit 131a Equipment control unit 131b Output optical power control unit 131c Received optical power measurement unit 131d Signal quality measurement unit 132 First calculation unit 133 Second calculation unit 901 CPU 902 Memory 903 Storage 904 Communication device 905 Input device 906 Output device

Claims

1. For an optical transmitter and an optical receiver connected via a transmission line, a measuring unit that measures the value of signal quality for each received optical power at the optical receiver, and using the measured value of signal quality for each received optical power at the optical receiver, a first calculation unit that calculates a first signal distortion caused by the optical transmitter and the optical receiver that depends on the received optical power, and a second signal distortion caused by the optical transmitter and the optical receiver that does not depend on the received optical power, and a second calculation unit that calculates the relationship between the signal quality and the transmission quality of the optical transmitter and the optical receiver by calculating the value of signal quality for each optical noise level using the first signal distortion, the second signal distortion, and a third signal distortion caused by the transmission line calculated from the optical noise level. An estimation device comprising the above components.

2. The first calculation unit calculates the first signal distortion and the second signal distortion such that the calculated value of signal quality calculated from the measured value of signal quality for each received optical power at the optical receiver and the value obtained by combining the first signal distortion and the second signal distortion multiplied by the received optical power match each other. The estimation device according to claim 1.

3. The second calculation unit calculates the signal distortion caused by the optical transmitter and the optical receiver when the received optical power is a predetermined value from the calculation results of the first signal distortion and the second signal distortion, calculates the third signal distortion corresponding to each optical noise level, and combines the two calculation results to calculate the value of signal quality for each optical noise level, thereby calculating the relationship between the signal quality and the transmission quality of the optical transmitter and the optical receiver. The estimation device according to claim 1.

4. The second calculation unit calculates the value of signal quality for each optical noise level for a predetermined received optical power using an equation that calculates the value of signal quality from the value obtained by combining the first signal distortion multiplied by the received optical power, the second signal distortion, and the third signal distortion, thereby calculating the relationship between the signal quality and the transmission quality of the optical transmitter and the optical receiver. The estimation device according to claim 1.

5. The measuring unit measures the value of signal quality for each received optical power at the optical receiver while changing the received optical power at the optical receiver by adjusting the output optical power on the optical transmission side. The estimation device according to claim 1.

6. In the estimation method performed by the estimation device, for an optical transmitter and an optical receiver connected via a transmission line, the value of the signal quality for each received optical power at the optical receiver is measured, and using the measured value of the signal quality for each received optical power at the optical receiver, a first signal distortion by the optical transmitter and the optical receiver that depends on the received optical power and a second signal distortion by the optical transmitter and the optical receiver that does not depend on the received optical power are calculated, and by calculating the value of the signal quality for each optical noise level using the first signal distortion, the second signal distortion, and a third signal distortion by the transmission line calculated from the optical noise level, the relationship between the signal quality and the transmission quality of the optical transmitter and the optical receiver is calculated. Estimation method.

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