Transmission path parameter estimation device and transmission path parameter estimation method

Abstract

To easily estimate the nonlinear constants of multiple spans.SOLUTION: A transmission path parameter estimation device 100 includes a storage unit that stores in advance a nonlinear phase rotation amount distribution calculated using time waveform data acquired from a receiver of a certain transmission path whose transmission path parameters are known, and a nonlinear phase rotation amount in another transmission path 120 whose transmission path parameters are different from the certain transmission path and are unknown, and a control unit that refers to the data stored in the storage unit and calculates a nonlinear constant of each span of the other transmission path 120 on the basis of the distribution of the nonlinear phase rotation amount.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a transmission path parameter estimation device and a transmission path parameter estimation method. [Background technology]

[0002] In a network system of transmission lines that transmit optical signals, in order to continue to efficiently handle large amounts of traffic, it is necessary to monitor the physical characteristics of the transmission lines even after the system has started operating.

[0003] As a technique related to monitoring the physical characteristics of a transmission line, a technique has been proposed for estimating the power change of the transmission line and the amount of chromatic dispersion and chromatic dispersion slope in each span of the transmission line based on signal data acquired from an optical receiver. For example, there is a technique that calculates the nonlinear constant and chromatic dispersion value by propagating four-wave mixing light from a CW light source through a non-measured optical fiber and measuring the optical power with an optical spectrum analyzer. There is also a technique that measures the chromatic dispersion characteristics of an optical fiber line by differentiating the phase difference for each wavelength of the signal light received by the optical receiver of the terminal station with respect to the wavelength. There is also a technique that calculates the chromatic dispersion by dividing the chromatic dispersion by the length of the span by assuming that the chromatic dispersion coefficient of an optical fiber span at a certain wavelength is the delay difference per unit wavelength between two signal lights propagating along a unit length of the optical fiber and that the chromatic dispersion coefficient along the span of the optical fiber is uniform. There is also a technique that transmits an optical pulse train signal through an optical fiber, monitors the nonlinear effect of the optical fiber link by dispersive Fourier transform, and calculates the chromatic dispersion (see, for example, Patent Documents 1 to 4 below). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-166904 A [Patent Document 2] JP 2002-357509 A [Patent Document 3] US Patent Application Publication No. 2010 / 0283996 [Patent Document 4] US Patent Application Publication No. 2017 / 0019172 Summary of the Invention [Problem to be solved by the invention]

[0005] The nonlinear constant of each span is useful information for optimal control of the entire optical transmission network, including the modulation method of the transmitter and receiver. However, currently, only methods have been proposed for measuring the nonlinear constant of the transmission line for each span, and no technology has been established for determining the nonlinear constant of each span of a multi-span transmission system at the receiving end.

[0006] In a multi-span transmission system, there is a demand for a technique that allows the receiving end to estimate the nonlinear constant of each span based on a received signal without adding new optical components or devices such as an optical spectrum analyzer.

[0007] In one aspect, the present invention aims to easily estimate the nonlinear constants of multiple spans. [Means for solving the problem]

[0008] According to one aspect of the present invention, a transmission path parameter estimation device includes: a storage unit that stores in advance a nonlinear phase rotation amount distribution calculated using time waveform data acquired from a receiver of a first transmission path and a nonlinear phase rotation amount in a second transmission path different from the first transmission path; and a control unit that refers to the data in the storage unit and calculates a nonlinear constant of each span of the second transmission path based on the distribution of the nonlinear phase rotation amount. Effect of the Invention

[0009] Advantageous Effects of Invention According to one aspect of the present invention, an effect is achieved in that the nonlinear constants of multiple spans can be easily estimated. [Brief description of the drawings]

[0010] [Figure 1]FIG. 1 is a functional block diagram of a channel parameter estimation device according to an embodiment. [Diagram 2] FIG. 2 is a chart showing an example of a distribution of the amount of nonlinear phase rotation in a transmission line. [Diagram 3] FIG. 3 is an explanatory diagram of axis conversion of the amount of nonlinear phase rotation. [Figure 4] FIG. 4 is an explanatory diagram of the results of estimating the fiber type using existing technology. [Diagram 5] FIG. 5 is a diagram illustrating an example of a hardware configuration of the transmission channel parameter estimation device. [Figure 6] FIG. 6 is an explanatory diagram of the nonlinear constant estimation process. [Figure 7] FIG. 7 is a flowchart showing an example of a process for estimating a nonlinear constant. [Figure 8] FIG. 8 is an explanatory diagram of the process of estimating the chromatic dispersion coefficient. [Figure 9] FIG. 9 is a flowchart illustrating an example of a process for estimating the chromatic dispersion coefficient. [Figure 10A] FIG. 10A is a diagram showing a configuration example for pre-calculating a reference value. [Figure 10B] FIG. 10B is a diagram showing a configuration example for pre-calculating a reference value. (Part 2) [Figure 11] FIG. 11 is a flowchart illustrating an example of a process for pre-calculating a reference value. [Figure 12] FIG. 12 is a chart showing the reference values ​​calculated by the simulation / measurement system. [Figure 13] FIG. 13 is an explanatory diagram of a transmission line model. [Figure 14] FIG. 14 is a flowchart showing an example of constructing a transmission channel model using estimated values ​​of nonlinear constants. [Figure 15] FIG. 15 is a functional block diagram showing an example of application to fiber type identification. [Figure 16] FIG. 16 is a flowchart showing an example of fiber type identification using an estimated value of a nonlinear constant. [Figure 17] FIG. 17 is a functional block diagram showing another application example to fiber type identification. [Figure 18] FIG. 18 is a flowchart showing an example of a process for identifying the fiber type. [Figure 19] FIG. 19 is a chart showing the distribution of the amount of phase rotation to be estimated. [Figure 20] FIG. 20 is an explanatory diagram of the estimation of the chromatic dispersion coefficient using the existing power profile estimation. [Figure 21] FIG. 21 is a chart showing examples of fiber specifications. [Figure 22] FIG. 22 is a flow chart illustrating an example of fiber type identification using existing power profile estimation. [Figure 23A] FIG. 23A is a chart showing an example of a power profile of an optical path according to existing power profile estimation. [Figure 23B] FIG. 23B is a chart showing various data used to identify fiber type using existing power profile estimation. [Figure 24] FIG. 24 is a functional block diagram of a transmission line parameter estimating apparatus according to an embodiment for identifying a fiber type. [Diagram 25] FIG. 25 is a chart showing various data used for fiber type identification. [Figure 26] FIG. 26 is a flowchart of an example of a process of identifying fiber types of multiple spans according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the disclosed transmission path parameter estimation device will be described in detail with reference to the drawings.

[0012] (Example of the configuration of a transmission path parameter estimation device according to an embodiment) FIG. 1 is a functional block diagram of a transmission path parameter estimation device according to an embodiment. The transmission path parameter estimation device 100 estimates physical characteristics (transmission path parameters) of a transmission path based on a received waveform of a digital coherent device. For example, the transmission path parameter estimation device 100 analyzes changes in the amount of phase rotation and the amount of dispersion (height and inclination) at each point based on distribution information of the amount of nonlinear phase rotation on the transmission path obtained from a received signal, and compares it with information (reference value) obtained under known conditions. In this way, unknown transmission path parameters, for example, a chromatic dispersion coefficient and a nonlinear constant, are estimated. The known information can be obtained, for example, from design information of the transmission path managed by a manager of the transmission path, and is obtained by operation input by the manager or by referring to a design information database.

[0013] The transmission path parameter estimation device 100 is mounted as one function on the receiver (Rx) side of an optical transceiver connected to a transmission path 120 such as an optical fiber. Fig. 1 shows an optical receiving unit 130 of a digital coherent optical transceiver. In the optical receiving unit 130, a digital coherent reception processing unit 131 receives and processes a digital coherent optical signal light, and a digital signal processing unit 132 demodulates the received signal and outputs demodulated data.

[0014] The transmission channel parameter estimation apparatus 100 acquires data related to transmission channel parameter estimation from a digital coherent reception processing unit 131 or a digital signal processing unit 132. The transmission channel parameter estimation apparatus 100 has each function of a control unit that estimates the transmission channel parameters of a transmission channel 120. The control unit includes, as each function, a nonlinear phase rotation amount estimation unit 111, a span detection unit 112, a reference value acquisition unit 113, a chromatic dispersion coefficient estimation unit 114, and a nonlinear constant estimation unit 115.

[0015] The nonlinear phase rotation estimation unit 111 estimates the distribution of the amount of nonlinear phase rotation at each point on the transmission path 120 as a function of the amount of accumulated chromatic dispersion from the transmitting end, from the signal strength information of the received signal collected from the optical receiving unit 130. The signal strength information is time waveform data with a different value for each time.

[0016] The span detection unit 112 detects each span corresponding portion for each span in the nonlinear phase rotation amount distribution estimated by the nonlinear phase rotation amount estimation unit 111. The reference value acquisition unit 113 acquires a reference value of the nonlinear phase rotation amount under known transmission conditions from a storage unit for the transmission path 120. The reference value includes a nonlinear phase rotation amount distribution at each point of a transmission path whose transmission path parameters are known and which is different from the transmission path 120 to be estimated.

[0017] The chromatic dispersion coefficient estimation unit 114 calculates an estimate of the chromatic dispersion coefficient of each span based on the nonlinear phase rotation amount distribution estimated by the nonlinear phase rotation amount estimation unit 111, the fiber length of each span detected by the span detection unit 112, and the reference value acquired by the reference value acquisition unit 113.

[0018] The nonlinear constant estimating unit 115 calculates an estimate of the nonlinear constant of each span based on the nonlinear phase rotation amount distribution, each span corresponding portion, the reference value, the estimate of the chromatic dispersion coefficient, and known fiber input power information. Each functional unit will be described in detail below.

[0019] (Overview of Transmission Line Parameter Estimation) Figure 2 is a chart showing an example of the distribution of nonlinear phase rotation in a transmission line. The horizontal axis of Figure 2 is chromatic dispersion step, which shows the cumulative value of chromatic dispersion in steps per km, which is equivalent to the distance between the transmitter (Tx) at the sending end of the signal light and the receiver (Rx) at the receiving end, and the vertical axis shows the relative phase rotation distribution [dB].

[0020] In the example of Fig. 2, there are five spans between Tx and Rx, and the phase rotation distribution of each span has a certain height and gradient corresponding to the optical power. Here, (1) the phase rotation amount of each span changes in the vertical axis direction according to the nonlinear effect and chromatic dispersion coefficient of the transmission line 120. In the example of Fig. 2, the peak p of the gradient ψ3 of the phase rotation amount at the start end of the third span is located higher (+2) in the positive direction than the reference (0).

[0021] In addition, (2) the slope of the dispersion change changes depending on the chromatic dispersion coefficient. In the example of Fig. 2, the slope ψ3 of the phase rotation amount in the third span is steeper than the slope ψ4 of the phase rotation amount in the fourth span.

[0022] Based on these (1) and (2), for the phase rotation distribution shown in Figure 2, (3) compare the phase rotation distribution obtained from the received signal with existing reference values ​​obtained in advance by simulation or a measurement system with known conditions. This allows the transmission path parameters (chromatic dispersion coefficient and nonlinear constant) at unknown points to be estimated.

[0023] In this embodiment, the transmission path parameters are estimated based on the following equation. The following formula (1) is a nonlinear Schrodinger equation, the following formula (2) is a nonlinear constant, and the following formula (3) is self-phase modulation (dispersion axis representation).

[0024]

number

[0025]

number

[0026]

number

[0027] Figure 3 is an explanatory diagram of axis conversion of the nonlinear phase rotation amount. In the above formula (3), D(z) corresponds to the wavelength dispersion coefficient. The distance axis L(z)=d / D(z), where d is equivalent to one scale of the dispersion axis, converts the distance axis L(z) with non-uniform axis spacing into a uniform dispersion axis d by calculating ×D(z).

[0028] In the embodiment, a change in the gradient ψ of the amount of nonlinear phase rotation displayed on the dispersion axis is detected based on the following formula (4): The ratio of the chromatic dispersion coefficients is obtained based on the gradient ψ of the amount of nonlinear phase rotation.

[0029]

number

[0030] In addition, the change in the amount of phase rotation due to self-phase modulation in the amount of nonlinear phase rotation displayed on the dispersion axis (frequency ω is assumed to be constant) is calculated based on the following formula (5). φ is the amount of phase rotation, κ is the nonlinear constant, D is the chromatic dispersion coefficient, and P is the fiber input power. φ1, κ1, D1, and P1 are reference values ​​obtained from a simulation / measurement system with known conditions. φ2, κ2, D2, and P2 are values ​​of the transmission path to be estimated, and the calculation method will be described later. In addition, the fiber input power P2 is obtained from the monitor information. In addition, 10logφ2 / φ0-10logφ1 / φ0 indicates the change in the height direction, and κ2 / κ1 is proportional to the nonlinear constant. D2 / D1 is the ratio of the chromatic dispersion coefficient, and P2 / P1 is the power ratio.

[0031]

number

[0032] (Issues with existing technology) Here, the issues with the existing technology will be explained. An example will be explained in which the fiber type of each span of a transmission path is estimated based on an estimated nonlinear constant. With the existing technology, if the fiber type cannot be determined from the chromatic dispersion coefficient alone, it is necessary to analyze multiple wavelength paths on the same route to find the dispersion slope. As a result, with the existing technology, 1. It requires calculation costs equivalent to the number of wavelengths. 2. It requires data for multiple wavelengths, and is limited to cases where data for multiple wavelengths can be obtained.

[0033] In contrast, in the embodiments, the nonlinear constant can be estimated from one wavelength path. Then, by narrowing down the fiber types based on the estimated nonlinear constant, it becomes unnecessary to obtain the dispersion slope, and the problems with the existing technology described above can be solved. In the embodiments, the fiber type of each span of the transmission line can be estimated with one wavelength, the number of wavelengths can be reduced, and calculation costs can be reduced. In the embodiments, for example, it becomes possible to efficiently estimate the type of fiber installed in each span of the transmission line. In addition, it becomes possible to prevent the effects of performance degradation, such as a reduction in SNR margin due to incorrect fiber connection.

[0034] Figure 4 is an explanatory diagram of the results of fiber type estimation using existing technology. Figure 4(a) shows the estimated fiber type for each span of the transmission line. Figure 4(b) is a fiber specification table, showing the chromatic dispersion coefficient (CD) and nonlinear constant (n2 / A eff ) minimum and maximum values.

[0035] Using only the chromatic dispersion coefficient estimated using existing technology, it is not possible to determine whether the fiber type in the sixth span in Figure 4(a) is ELEAF or TWRS. ELEAF stands for Enhanced Large Effective Area Fiber, and TWRS stands for TrueWave Reduced Slope.

[0036] In contrast, according to the embodiment, the nonlinear constant of the sixth span is estimated and compared with a threshold value of the nonlinear constant (for example, 0.34), thereby making it possible to distinguish between ELEAF and TWRS.

[0037] The nonlinear constant range can be calculated based on the following technical documents. The specification sheets for the fiber types are disclosed in the following technical documents 1 and 2.

[0038] Technical document 1: "Corning(R) LEAF(R) Optical Fiber Product Information", [online], retrieved June 15, 2023, URL: https: / / www.corning.com / media / worldwide / coc / documents / Fiber / product-information-sheets / PI-1107-AEN.pdf, Corning Incorporated.

[0039] Technical document 2: "TrueWave(R) RS Optical Fiber", [online], retrieved June 15, 2023, URL: https: / / fiber-optic-catalog.ofsoptics.com / documents / pdf / TrueWaveRSLWP-120-web.pdf, OFS Fitel, LLC.

[0040] Check the Mean Field Diameter (MFD) from the spec sheets in technical documents 1 and 2, and use ELEAF (0.4 μm) and TWRS (0.6 μm) as the MFD errors.

[0041] In addition, the MFD and A are calculated from the formulas on p. 39 (II-3) and (II-4) of Technical Reference 3. eff The relationship is obtained.

[0042] Technical document 3: “SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS, Transmission media and optical systems characteristics-Optical fibre cables”, retrieved on June 15, 2023, URL: https: / / www.itu.int / rec / T-REC-G.650.2-201508-I / en, G650.2(08·2015), ITU-T.

[0043] And, from the formula (2) in Technical Reference 4, A effThe relationship between n2 and the nonlinear constant (n2 / A eff ) is calculated.

[0044] Technical document 4: “Nonlinear empirical equations of (n2 / A eff ) and n2 for various Ge-doped single mode optical fibers”,[online],Retrieved June 15, 2023,URL:https: / / ieeexplore.ieee.org / document / 4610335,07-10 July 2008,OECC / ACOFT 2008 - Joint Conference of the Opto-Electronics and Communications Conference and the Australian Conference on Optical Fiber Technology,IEEE.

[0045] (Example of hardware configuration of a transmission path parameter estimation device) 5 is a diagram showing an example of a hardware configuration of a channel parameter estimation apparatus 100. For example, the channel parameter estimation apparatus 100 can be configured using general-purpose hardware shown in FIG.

[0046] For example, the channel parameter estimation apparatus 100 includes a processor 501 such as a CPU (Central Processing Unit), a memory 502, a network IF 503, a recording medium IF 504, and a recording medium 505. The components are connected to each other via a bus 500.

[0047] Here, the processor 501 is a control unit that controls the channel parameter estimation device 100. The processor 501 may have multiple cores. The memory 502 has, for example, a read only memory (ROM), a random access memory (RAM), and a flash ROM. Specifically, for example, the flash ROM stores a control program, the ROM stores an application program, and the RAM is used as a work area for the processor 501. The program stored in the memory 502 is loaded into the processor 501 to cause the processor 501 to execute the coded process.

[0048] The network IF 503 serves as an interface between the network NW and the transmission path parameter estimation apparatus 100, and controls the input and output of information between the network NW and the transmission path parameter estimation apparatus 100 and the outside.

[0049] The recording medium IF 504 controls reading / writing of data from / to the recording medium 505 under the control of the processor 501. The recording medium 505 stores data written under the control of the recording medium IF 504.

[0050] In addition to the above-mentioned components, the transmission path parameter estimation apparatus 100 may be configured to be connectable to, for example, an input device, a display, and the like via an IF.

[0051] The processor 501 shown in Fig. 5 can realize the functions of the channel parameter estimation device 100 shown in Fig. 1 by executing a program. The memory 502 and recording medium 505 shown in Fig. 5 can be used to realize the functions of the storage unit that stores the above-mentioned reference values.

[0052] The hardware configuration of the transmission path parameter estimation apparatus 100 shown in Fig. 5 can also be one function of a control unit of an optical transceiver having the transmission path parameter estimation apparatus 100. In this case, the hardware configuration shown in Fig. 5 realizes a function related to the transmission path parameter estimation by the transmission path parameter estimation apparatus 100 of the embodiment in addition to a function related to the optical transmission and reception processing of the optical receiving unit 130 or the entire optical transceiver including the optical receiving unit 130.

[0053] Next, each function of the channel parameter estimation apparatus 100 according to the embodiment will be described in detail.

[0054] (Estimation of nonlinear constants) Fig. 6 is an explanatory diagram of the estimation process of the nonlinear constant. An example of the process of the transmission channel parameter estimation device 100 (mainly the nonlinear constant estimation unit 115) will be described. The transmission channel parameter estimation device 100 estimates the nonlinear constant of the estimation target by comparing a reference value (nonlinear phase rotation amount distribution) acquired and calculated from a simulation / measurement system shown in Fig. 6(a) with the nonlinear phase rotation amount distribution of the estimation target transmission channel shown in Fig. 6(b).

[0055] The transmission line parameter estimation device 100 estimates the nonlinear constant of the transmission line 120 to be estimated based on the above formula (5). In the above formula (5), the reference values ​​include the phase rotation amount φ1, the nonlinear constant κ1, the chromatic dispersion coefficient D1, and the fiber input power P1. The phase rotation amount φ2, the nonlinear constant κ2, the chromatic dispersion coefficient D2, and the fiber input power P2 to be estimated are the respective values ​​of the nonlinear phase rotation amount distribution of the transmission line to be estimated. The chromatic dispersion coefficient is estimated by the chromatic dispersion coefficient estimation unit 114. Also, the fiber input power P2 is acquired from monitor information.

[0056] 7 is a flowchart showing an example of a process for estimating a nonlinear constant. An example of the process of the transmission channel parameter estimation apparatus 100 (processor 501) will be described. First, the transmission channel parameter estimation apparatus 100 acquires received waveform data of a received signal (step S701). Next, the transmission channel parameter estimation apparatus 100 calculates a nonlinear phase rotation amount distribution (FIG. 6(b)) of the transmission channel 120 to be estimated (step S702). The nonlinear phase rotation amount distribution corresponds to a power profile of the transmission channel 120.

[0057] Next, the channel parameter estimation apparatus 100 detects a peak corresponding to the start end of one span to be estimated (step S703). The span to be estimated is enclosed by a dotted line in FIG. 6(b), and peak p at the start end of the span to be estimated is detected.

[0058] Next, the transmission line parameter estimation apparatus 100 acquires a reference value calculated in advance (step S704). Next, the transmission line parameter estimation apparatus 100 estimates a chromatic dispersion coefficient of the span to be estimated (step S705). The estimation of the chromatic dispersion coefficient of the span to be estimated will be described in detail later.

[0059] Next, the transmission line parameter estimation apparatus 100 acquires the amount of nonlinear phase rotation φ2 at the position of the detected peak p (step S706).Then, the transmission line parameter estimation apparatus 100 estimates the nonlinear constant of one span to be estimated using the reference value, the amount of nonlinear phase rotation of the estimation target portion, the chromatic dispersion coefficient, and the fiber input power (step S707), and ends the process.

[0060] The reference values ​​include the nonlinear phase rotation amount φ1, the nonlinear constant, the chromatic dispersion coefficient, and the fiber input power shown in Fig. 6(a). The transmission line parameter estimation device 100 estimates the nonlinear constant of the span to be estimated by substituting each value into the above formula (5), and outputs the estimated value.

[0061] The transmission channel parameter estimation apparatus 100 estimates the nonlinear constants of all spans of the transmission channel 120 by changing the span to be estimated and repeatedly executing the above process of FIG.

[0062] (About chromatic dispersion coefficient estimation) Fig. 8 is an explanatory diagram of the estimation process of the chromatic dispersion coefficient. An example of the process of the transmission line parameter estimation device 100 (mainly the chromatic dispersion coefficient estimation unit 114) will be described. The transmission line parameter estimation device 100 estimates the chromatic dispersion coefficient of the estimation target based on the reference value shown in Fig. 8(a) and the slope ratio of the nonlinear phase rotation amount distribution of the estimation target shown in Fig. 8(b) (the above formula (4)).

[0063] In the above equation (5), the slope of the phase rotation amount of the reference value is ψ1, the chromatic dispersion coefficient is D1, the slope of the phase rotation amount obtained from the phase rotation amount distribution of the transmission path to be estimated is ψ2, and the chromatic dispersion coefficient is D2.

[0064] The transmission line parameter estimation apparatus 100 compares the gradient of the nonlinear phase rotation amount distribution (expressed in dB) with a reference value to estimate the chromatic dispersion coefficient D2 of the span to be estimated.

[0065] 9 is a flowchart showing an example of a process for estimating a chromatic dispersion coefficient. An example of the process of the transmission channel parameter estimation apparatus 100 (processor 501) will be described. First, the transmission channel parameter estimation apparatus 100 acquires received waveform data of a received signal (step S901). Next, the transmission channel parameter estimation apparatus 100 calculates a nonlinear phase rotation amount distribution (FIG. 6(b)) of the transmission channel 120 to be estimated (step S902). The nonlinear phase rotation amount distribution corresponds to a power profile of the transmission channel 120.

[0066] Next, the channel parameter estimation apparatus 100 detects a peak corresponding to the start end of one span to be estimated (step S903). The span to be estimated is enclosed by a dotted line in FIG. 8(b), and peak p at the start end of the span to be estimated is detected.

[0067] Next, the channel parameter estimation apparatus 100 acquires a reference value calculated in advance (step S904). Next, the channel parameter estimation apparatus 100 calculates the gradient of the nonlinear phase rotation distribution in the region near the peak p (step S905). For example, the gradient ψ2 of the peak p in the region of the span to be estimated shown in FIG. 8(b) is calculated.

[0068] Next, the transmission path parameter estimation apparatus 100 estimates the chromatic dispersion coefficient of the estimation target point using the reference value and the gradient of the estimation target point (step S906), and ends the process.

[0069] The transmission line parameter estimation apparatus 100 estimates the chromatic dispersion coefficients of all spans of the transmission line 120 by changing the span to be estimated and repeatedly executing the above-described process of FIG.

[0070] Note that the processes of steps S701 to S704 in Fig. 7 are similar to the processes of steps S901 to S904 in Fig. 9. For example, the channel parameter estimation apparatus 100 may store the process results of steps S701 to S704 in Fig. 7 and use them in the process of step S905 in Fig. 9.

[0071] (Example of a configuration in which reference values ​​are pre-calculated) 10A and 10B are diagrams showing configuration examples for pre-calculating a reference value. Fig. 10A shows a configuration example including a reference value calculation unit 1010 that pre-calculates a reference value by, for example, a simulation on a computer. Also, the reference value calculation unit 1010 shown in Fig. 10B shows a configuration example for calculating a reference value by pre-measuring an actual transmission path using a measurement system.

[0072] Of the components shown in FIG. 10A, the functions of the optical receiving unit 1030 include a transmission signal generating unit 1001, an optical fiber transmission calculating unit 1002, a digital coherent receiving processing calculating unit 1031, and a digital signal processing calculating unit 1032.

[0073] The transmission signal generation unit 1001 generates a transmission signal according to a predetermined input signal type. The optical fiber transmission calculation unit 1002 calculates the transmission characteristics of the optical fiber based on the input chromatic dispersion coefficient, nonlinear constant, fiber input power, and transmission path information. The digital coherent reception processing calculation unit 1031 performs calculation processing related to digital coherent reception. The digital signal processing calculation unit 1032 performs calculation processing related to signal processing for digital signal demodulation.

[0074] The functions of reference value calculation section 1010 include nonlinear phase rotation amount estimator 1011, span detector 1012, and reference value extractor 1013. The functions of reference value calculation section 1010 (nonlinear phase rotation amount estimator 1011, span detector 1012, and reference value extractor 1013) are almost the same as those of nonlinear phase rotation amount estimator 111, span detector 112, and reference value acquisition section 113 in Fig. 1. The difference is that the reference values ​​are generated by executing a simulation.

[0075] 1, the reference value acquisition unit acquires a reference value, whereas in FIG. 10A, the reference value is extracted, and therefore is indicated as a reference value extraction unit 1013.

[0076] The nonlinear phase rotation amount estimator 1011 acquires data resulting from a simulation performed by the digital coherent reception processing calculator 1031 or the digital signal processing calculator 1032 .

[0077] The reference value extracting unit 1013 outputs the tilt, the amount of nonlinear phase rotation, the chromatic dispersion coefficient, the nonlinear constant, and the fiber input power as simulated reference values.

[0078] Fig. 10B shows an example of a configuration in which a reference value is calculated in advance by a measurement system. In the example of the configuration shown in Fig. 10B, components similar to those in Fig. 1 and Fig. 10A are given the same reference numerals.

[0079] The optical receiving unit 130 includes a digital coherent reception processing unit 131 and a digital signal processing unit 132 similar to those in Fig. 1. Furthermore, the transmission signal generating unit 1001 generates a transmission signal according to a predetermined signal type that is input.

[0080] The functions of reference value calculation section 1010 include nonlinear phase rotation amount estimator 1011, span detector 1012, and reference value extractor 1013, similar to those in FIG. 10A.

[0081] 10A and 10B, the functions of the reference value calculation unit 1010 are similar to those of the channel parameter estimation device 100 shown in FIG. 1, and the reference values ​​can be calculated in advance by computer processing similar to that of FIG. 1. For this reason, for example, the functions shown in FIG. 1 can be used for the functions shown in FIG. 10A and 10B. For example, components with similar functions are the nonlinear phase rotation estimation unit 1011 to the reference value extraction unit 1013. In addition, a digital coherent reception processing calculation unit 1031 and a digital signal processing calculation unit 1032 may be included.

[0082] Fig. 11 is a flowchart showing an example of a process for pre-calculating a reference value. Fig. 12 is a table showing reference values ​​calculated by a simulation / measurement system. An example of a process by the reference value calculation unit 1010 (processor 501) in Figs. 10A and 10B will be described.

[0083] First, the reference value calculation unit 1010 acquires received waveform data of a received signal in a simulation / or measurement system with known conditions (step S1101). Next, the reference value calculation unit 1010 calculates a nonlinear phase rotation amount distribution (FIG. 12) of the simulation / or measurement system with known conditions (step S1102). The nonlinear phase rotation amount distribution corresponds to the power profile of the transmission path 120.

[0084] Next, the reference value calculation unit 1010 detects a peak corresponding to the start end of one span to be referenced (step S1103). For example, the dotted frame in Fig. 12 is the reference span, and peak p at the start end of the reference span is detected.

[0085] Next, the reference value calculation unit 1010 calculates the slope of the nonlinear phase rotation distribution at the peak position in the reference span region and the peak value of the nonlinear phase rotation (step S1104). For example, the value of peak p and the slope ψ1 in the reference span region shown in FIG.

[0086] Next, the reference value calculation unit 1010 holds the calculated tilt and nonlinear phase rotation amount as reference values ​​together with the nonlinear constant, chromatic dispersion coefficient, and fiber input power of the reference span in the simulation / measurement system (step S1105), and ends the process. The calculated reference value is stored and held in a storage unit such as the memory 502, and is read out from the storage unit by the reference value acquisition unit 113 (FIG. 1) when estimating the transmission path parameters to be estimated.

[0087] (Example of application to constructing a transmission line model) Next, an example of application to constructing a transmission channel model will be described. The transmission channel parameters estimated by the above-mentioned embodiment can be used as input parameters for constructing a transmission channel model that simulates the transmission channel to be estimated. The transmission channel model can be, for example, a transmission simulation model or a transmission quality (QoT) estimation model.

[0088] Fig. 13 is an explanatory diagram of a transmission line model. In the transmission system shown in Fig. 13(a), at the transmitting end of the signal light, the signal light of an optical transmitter (Tx) 1301 for each wavelength is multiplexed by a MUX 1302 and transmitted. On the transmission line 120, the signal light is optically amplified by a plurality of optical amplifiers 1303 arranged at predetermined distances (e.g., 80 km) corresponding to the span. At the receiving end of the signal light, the signal light is wavelength-demultiplexed by a DEMUX 1304, and the signal light of each wavelength is received and processed by an optical receiver (Rx) 1305 for each wavelength.

[0089] 13(b) is a model that simulates the transmission line 120, and has input parameters such as a nonlinear constant, a chromatic dispersion coefficient, a fiber input power, a span loss, and a span length. The transmission line model 1310 models the transmission line 120 based on these input parameters. Then, the nonlinear constant estimated in the above-described embodiment is input to the transmission line model 1310.

[0090] 14 is a flowchart showing an example of constructing a channel model using estimated values ​​of nonlinear constants. A processing example of constructing the channel model shown in FIG. 13 by processing of the channel parameter estimation device 100 (processor 501) will be described.

[0091] The processes in steps S1401 to S1407 in Fig. 14 are the same as those in steps S701 to S707 in Fig. 7. First, the transmission channel parameter estimation apparatus 100 acquires received waveform data of a received signal (step S1401). Next, the transmission channel parameter estimation apparatus 100 calculates a nonlinear phase rotation amount distribution of the transmission channel 120 to be estimated (step S1402).

[0092] Next, the channel parameter estimation apparatus 100 detects a peak corresponding to the start end of one span to be estimated (step S1403).

[0093] Next, the transmission path parameter estimation apparatus 100 acquires a reference value calculated in advance (step S1404) Next, the transmission path parameter estimation apparatus 100 estimates a chromatic dispersion coefficient of the span to be estimated (step S1405).

[0094] Next, the transmission line parameter estimation apparatus 100 acquires the amount of nonlinear phase rotation at the detected peak position (step S1406).Then, the transmission line parameter estimation apparatus 100 estimates the nonlinear constant of one span to be estimated by using the reference value, the amount of nonlinear phase rotation at the estimation target location, the chromatic dispersion coefficient, and the fiber input power (step S1407).

[0095] In the process of step S1407, the channel parameter estimation apparatus 100 estimates the nonlinear constant of the span to be estimated by substituting each value into the above equation (5), and outputs the estimated value.

[0096] The transmission channel parameter estimation apparatus 100 estimates the nonlinear constants of all spans of the transmission channel 120 by changing the span to be estimated and repeatedly executing the above process of FIG.

[0097] After that, the channel parameter estimation apparatus 100 inputs the estimated value (nonlinear constant) to the input parameter of the channel model related to the channel to be estimated (step S1408), and ends the process. The nonlinear constant has a predetermined value for each span of the channel 120.

[0098] This makes it possible to construct a transmission path model 1310 that reflects the actual state of the transmission path 120. The transmission path model is, for example, a transmission simulation model, a transmission quality (QoT) estimation model, etc., and it becomes possible to improve the estimation accuracy of the transmission simulation and the transmission quality in these transmission path models 1310. Here, in the transmission path parameter estimation device 100 of the embodiment, the transmission path parameters can be estimated using only a single wavelength among multiple wavelength paths of the same route, so that the calculation cost can be reduced and the estimation can be performed easily.

[0099] (Example of application to fiber type identification) Next, an example of application to fiber type identification will be described. By using transmission line parameters such as the estimated nonlinear constant, the fiber type (fiber category) of each span of the transmission line 120 can be identified.

[0100] Fig. 15 is a functional block diagram showing an application example to fiber type identification. Among the functions of the transmission path parameter estimation device 100 shown in Fig. 15, the same reference numerals are used for the functions explained in Fig. 1. In Fig. 15, a function different from that in Fig. 1 is that a threshold determination unit 1501 is provided after the nonlinear constant estimation unit 115.

[0101] The transmission line parameters (chromatic dispersion coefficient, nonlinear constant, etc.) of the transmission line 120 to be estimated, estimated by the nonlinear constant estimation unit 115, and information on various known fibers (chromatic dispersion coefficient, nonlinear constant) are input to the threshold determination unit 1501. The threshold determination unit 1501 sets a predetermined threshold corresponding to the information on various known fibers, and identifies the fiber type by comparing the transmission line parameters (chromatic dispersion coefficient, nonlinear constant, etc.) of the transmission line 120 to be estimated with the threshold.

[0102] 16 is a flowchart showing an example of fiber type identification using an estimated value of a nonlinear constant. An example of processing for identifying the fiber type by processing in the transmission line parameter estimation device 100 (processor 501) will be described.

[0103] The processes in steps S1601 to S1607 in Fig. 16 are similar to those in steps S701 to S707 in Fig. 7. First, the transmission channel parameter estimation apparatus 100 acquires received waveform data of a received signal (step S1601). Next, the transmission channel parameter estimation apparatus 100 calculates a nonlinear phase rotation amount distribution of the transmission channel 120 to be estimated (step S1602).

[0104] Next, the channel parameter estimation apparatus 100 detects a peak corresponding to the start end of one span to be estimated (step S1603).

[0105] Next, the transmission path parameter estimation apparatus 100 acquires a reference value calculated in advance (step S1604) Next, the transmission path parameter estimation apparatus 100 estimates a chromatic dispersion coefficient of the span to be estimated (step S1605).

[0106] Next, the transmission line parameter estimation apparatus 100 acquires the amount of nonlinear phase rotation at the detected peak position (step S1606).Then, the transmission line parameter estimation apparatus 100 estimates the nonlinear constant of one span to be estimated by using the reference value, the amount of nonlinear phase rotation at the estimation target location, the chromatic dispersion coefficient, and the fiber input power (step S1607).

[0107] In the process of step S1607, the transmission line parameter estimation apparatus 100 estimates the transmission line parameters (nonlinear constant, chromatic dispersion coefficient) of the span to be estimated by substituting each value into the above equation (5), and outputs the estimated values.

[0108] The transmission line parameter estimation apparatus 100 estimates the transmission line parameters (nonlinear constant, chromatic dispersion coefficient) of all spans of the transmission line 120 by changing the span to be estimated and repeatedly executing the above process of FIG.

[0109] Thereafter, the transmission line parameter estimation apparatus 100 compares the estimated values ​​(nonlinear constant, chromatic dispersion coefficient nonlinear constant) with a threshold determined from the fiber information, identifies the fiber type (step S1608), and ends the process.

[0110] This makes it possible to estimate the fiber type of the transmission line 120. For example, it becomes possible to estimate the fiber type of each span described in FIG. 4(a). More specifically, it becomes possible to efficiently estimate the fiber type of each span of the transmission line 120. It also becomes possible to prevent the influence of performance degradation such as a decrease in SNR margin caused by incorrect fiber connection. Furthermore, in the transmission line parameter estimation device 100 of the embodiment, it is possible to estimate the transmission line parameters using only a single wavelength among multiple wavelength paths of the same route, so that it is possible to reduce calculation costs and easily identify the fiber type.

[0111] (Example of application of identifying fiber type using known fiber type information as a reference value) In this application example, the estimated physical quantity is used to identify the type of fiber laid in the transmission line 120. However, as a reference value, information on the span where the fiber type could be identified by an existing method or the like is used.

[0112] Fig. 17 is a functional block diagram showing another application example to fiber type identification. Among the functions of the transmission path parameter estimation device 100 shown in Fig. 17, the functions explained in Fig. 15 are given the same reference numerals. A function different from Fig. 15 in Fig. 17 is that the reference value acquisition unit 113 in Fig. 15 is not provided. Also, a fiber type determination unit 1701 is provided between the rear stage of the chromatic dispersion coefficient estimation unit 114 and the nonlinear constant estimation unit 115.

[0113] Span length (fiber length) information is input to the chromatic dispersion coefficient estimating unit 114 in Fig. 17. The chromatic dispersion coefficient estimating unit 114 estimates the chromatic dispersion coefficient of the span from the span length data and the amount of chromatic dispersion between peaks.

[0114] The chromatic dispersion coefficient estimated by the chromatic dispersion coefficient estimating unit 114 and various types of fiber information (chromatic dispersion coefficient, nonlinear constant) are input to the fiber type determining unit 1701 and the threshold determining unit 1501. The fiber type determining unit 1701 identifies the fiber type from the estimated chromatic dispersion coefficient of the span, and stores the fiber type of the identified span and its physical characteristics as reference values ​​in a storage unit such as the memory 502. The fiber type determining unit 1701 also acquires the span for which the fiber type has been identified and the amount of nonlinear phase rotation of the peak position of the estimation target location of the transmission path 120.

[0115] Fig. 18 is a flowchart showing a processing example of fiber type identification. Fig. 19 is a chart showing a phase rotation amount distribution of an estimation target. A processing example of identifying the fiber type by processing of the transmission path parameter estimation apparatus 100 (processor 501) will be described.

[0116] First, the channel parameter estimation apparatus 100 acquires received waveform data of a received signal (step S1801). Next, the channel parameter estimation apparatus 100 calculates the distribution of the amount of nonlinear phase rotation of the channel 120 to be estimated (step S1802).

[0117] Next, the channel parameter estimation apparatus 100 detects a peak corresponding to the start end of each span to be estimated (step S1803).

[0118] Next, the transmission line parameter estimation apparatus 100 estimates the chromatic dispersion coefficient of each span from the span length data and the chromatic dispersion amount between peaks (step S1804). Next, the transmission line parameter estimation apparatus 100 stores the fiber type and its physical characteristics of the spans whose fiber type has been determined as shown in FIG. 19 as reference values ​​(step S1805).

[0119] Next, the transmission line parameter estimation apparatus 100 acquires the amounts of nonlinear phase rotation φ1 and φ2 of the span in which the fiber type has been determined and the position of the peak p at the estimation target location (step S1806).

[0120] Next, the transmission line parameter estimation apparatus 100 estimates the nonlinear constant of one span to be estimated by using the amount of nonlinear phase rotation, the chromatic dispersion coefficient, and the fiber input power of the estimation target location (step S1807).

[0121] In the process of step S1807, the transmission line parameter estimation apparatus 100 estimates the transmission line parameters (nonlinear constant, chromatic dispersion coefficient) of the span to be estimated by substituting each value into the above equation (5), and outputs the estimated values.

[0122] Thereafter, the transmission line parameter estimation apparatus 100 compares the estimated values ​​(nonlinear constant, chromatic dispersion coefficient nonlinear constant) with a threshold determined from the fiber information, and identifies the fiber type (step S1808).

[0123] The transmission line parameter estimation apparatus 100 estimates the transmission line parameters (nonlinear constant, chromatic dispersion coefficient) of all spans of the transmission line 120 by changing the span to be estimated and repeatedly executing the above process of FIG.

[0124] In this way, by using information on spans of fiber types that have already been identified among the multiple spans of the transmission line 120, the fiber type of the span to be estimated can also be estimated.

[0125] (Example of fiber type identification using existing technology) Next, an example of fiber type identification using existing techniques and the problems associated with it will be described. As an existing technique, a technique for estimating a chromatic dispersion coefficient using a power profile estimation (correlation method) has been disclosed (see, for example, Patent Documents 5 and 6 below).

[0126] Patent Document 5: JP 2018-133725 A Patent Document 6: U.S. Patent Application Publication No. 2018 / 0234184

[0127] Fig. 20 is an explanatory diagram of estimation of chromatic dispersion coefficient using existing power profile estimation. Fig. 20(a) shows an optical path, and similarly to Fig. 13, an optical transmitter (Tx) 1301 for each wavelength, a MUX 1302, multiple optical amplifiers 1303, a DEMUX 1304, and an optical receiver (Rx) 1305 are arranged. Fig. 20(b) shows the power profile of the optical path shown in Fig. 20(a), where the horizontal axis is the accumulated chromatic dispersion amount and the vertical axis is the correlation value.

[0128] Figure 21 is a chart showing an example of fiber specifications, showing the chromatic dispersion coefficients (CD) of SMF, ELEAF, and TWRS as fiber types.

[0129] Fig. 22 is a flowchart showing an example of fiber type identification using existing power profile estimation. A process example will be described in which the optical receiver (Rx) 1305 at the receiving end shown in Fig. 20(a) estimates the chromatic dispersion coefficient using power profile estimation and identifies the fiber type.

[0130] First, the received waveform data of the received signal is acquired (step S2201). Next, the power profile of the transmission path 120 is calculated (FIG. 20(b), step S2202). Next, the peaks corresponding to each span are detected (step S2203).

[0131] Next, the chromatic dispersion coefficient of each span is estimated from the span length data and the chromatic dispersion amount between the peaks (step S2204). If the chromatic dispersion coefficient information alone is insufficient to estimate the chromatic dispersion coefficient, the same estimation is repeated for multiple wavelengths (step S2205).

[0132] Next, the chromatic dispersion slope is estimated (step S2206). Then, the estimation result is compared with the fiber spec information (FIG. 21) to identify the fiber type of each span (step S2207), and the process ends.

[0133] Fig. 23A is a chart showing an example of a power profile of an optical path by existing power profile estimation, and Fig. 23B is a chart showing various data used when identifying a fiber type using existing power profile estimation.

[0134] The amount of chromatic dispersion between the peaks of each span is obtained by the power profile estimation shown in Fig. 22, and the chromatic dispersion coefficient of each span is obtained as shown in Fig. 23B(a). Section AB shown in Fig. 23A corresponds to span 1 in Fig. 23B(a). Similarly, section BC shown in Fig. 23A corresponds to span 2 in Fig. 23B(a).

[0135] FIG. 23B(b) is a chart showing fiber specs similar to FIG. 21, and FIG. 23B(c) is a chart showing the estimated fiber type for each span.

[0136] Here, in the power profile shown in FIG. 23A, the peak p of the accumulated chromatic dispersion amount (correlation value) at the start end of section FG is higher than in the other sections, and correspondingly, the value of the chromatic dispersion coefficient of span 6 shown in FIG. 23B(a) (4.24) is lower than in the other sections.

[0137] Suppose we compare the estimated chromatic dispersion coefficient value (4.24) of span 6 with the fiber spec table in Fig. 23B(b). In this case, as shown in Fig. 23B(c), we cannot determine whether the fiber type of span 6 is ELEAF (CD: 3.303 to 4.401) or TWRS (CD: 3.307 to 5.131).

[0138] In this way, it may not be possible to identify the fiber type only from the results of estimating the chromatic dispersion coefficient using the power profile estimation of the existing technology. In this case, with the existing technology, it becomes necessary to calculate the power profile for each of the different wavelengths for the transmission line 120 and obtain the chromatic dispersion slope. As a result, with the existing technology, 1. It requires calculation costs equivalent to the number of wavelengths. 2. It requires data for multiple wavelengths, and is limited to cases where data for multiple wavelengths can be obtained.

[0139] (Fiber type identification function) Fig. 24 is a functional block diagram of a transmission line parameter estimating device according to an embodiment for identifying fiber type. In Fig. 24, the same components as those in Fig. 1 are denoted by the same reference numerals. As shown in Fig. 24, a span information vector creating unit 2401 and an evaluating unit 2402 are provided after the nonlinear constant estimating unit 115 as a function of identifying fiber type.

[0140] The span information vector creation unit 2401 receives the nonlinear constant of each span estimated by the nonlinear constant estimation unit 115 and various fiber information (chromatic dispersion coefficient, nonlinear constant), and creates a span information vector that lists the chromatic dispersion coefficients and nonlinear constants of multiple spans. The span information vector includes a chromatic dispersion coefficient V_cd and a nonlinear constant V_nl. It is assumed here that the fiber type candidates for each span are known in advance. The span information vector creation unit 2401 also reduces the number of combination patterns by extracting only spans whose fiber type is unspecified. For example, it extracts spans that cannot be estimated using existing technology.

[0141] The evaluation unit 2402 determines a vector for each arrangement pattern based on fiber spec data, and calculates the distance from the estimated vector as an evaluation value. For example, the evaluation unit 2402 calculates the sum of the Euclidean distance of the chromatic dispersion coefficient and the Euclidean distance of the nonlinear constant, and sets the sum as the evaluation value. The evaluation unit 2402 identifies the fiber type indicated by the pattern with the smallest evaluation value among the evaluation values ​​calculated for each pattern.

[0142] Fig. 25 is a chart showing various data used for fiber type identification. Fig. 25(a) is a fiber spec table, and Fig. 25(b) is a chart showing evaluation information (chromatic dispersion coefficient, nonlinear constant, calculated evaluation value) for each arrangement pattern. In the example of Fig. 25(b), the pattern shows a combination of two fiber types (ELEAF and TWRS) in three spans, the chromatic dispersion coefficient shows the chromatic dispersion coefficient of each of the three spans, and the nonlinear constant shows the nonlinear constant of each of the three spans.

[0143] For example, as shown in Fig. 25, a case will be described in which there are two types of installed fiber candidates, ELEAF and TWRS, in a path with a three-span configuration. In this case, the span information vector creation unit 2401 creates span information vectors V_cd (3.56, 4.83, 3.6) and V_nl (0.28, 0.44, 0.3) from the estimation result.

[0144] The evaluation unit 2402 determines a vector for each arrangement pattern based on the fiber spec data, and calculates an evaluation value (the distance from the estimated vector).The evaluation unit 2402 then identifies the pattern with the smallest evaluation value among the evaluation values ​​calculated for each pattern, and identifies the fiber type.In the example of Fig. 25, the smallest evaluation value is 0.74, and the fiber type is identified as ELEAF-TWRS-ELEAF from the corresponding 3-span configuration pattern.

[0145] 26 is a flowchart illustrating an example of a process for identifying the fiber type of multiple spans according to the embodiment. A process for identifying the fiber type of multiple spans by the process of the transmission path parameter estimation device 100 (the processor 501) illustrated in FIG.

[0146] First, the transmission path parameter estimation apparatus 100 estimates the chromatic dispersion coefficient and the nonlinear constant of each span by the process described in the above embodiment (e.g., see FIG. 7), and creates a span information vector (V_cd, V_nl) (step S2601).

[0147] Next, the transmission line parameter estimation apparatus 100 creates span information vectors (Vn_cd, Vn_nl) for each arrangement pattern n based on the fiber type candidates and fiber spec information for each span (step S2602).

[0148] Next, the channel parameter estimation apparatus 100 calculates the sum of the Euclidean distance between the span information vectors V_cd and Vn_cd and the Euclidean distance between the span information vectors V_nl and Vn_nl, and sets the sum as an evaluation value (step S2603). For example, (|Vn_cd-V_cd|+|Vn_nl-V_nl|) is calculated.

[0149] Next, the transmission path parameter estimation apparatus 100 specifies the pattern that minimizes the evaluation value, identifies the fiber type (step S2604), and ends the above process.

[0150] As described above, in the embodiment, the fiber type is narrowed down based on the nonlinear constant estimated from one wavelength path, and thus it becomes possible to identify the fiber type of each of multiple spans without the need to calculate the dispersion slope. In this way, in the embodiment, the number of wavelengths required to estimate the fiber type of each span of the transmission line can be reduced, and the calculation cost can be reduced. In the embodiment, for example, it becomes possible to efficiently estimate the type of installed fiber in each span of the transmission line. In addition, it becomes possible to prevent the influence of performance degradation such as a decrease in SNR margin due to incorrect fiber connection.

[0151] The transmission line parameter estimation device according to the embodiment described above includes a storage unit that stores in advance a nonlinear phase rotation amount distribution calculated using time waveform data acquired from a receiver of a first transmission line and a nonlinear phase rotation amount in a second transmission line different from the first transmission line, and a control unit that refers to the data in the storage unit and calculates a nonlinear constant of each span of the second transmission line based on the distribution of the nonlinear phase rotation amount. This makes it possible to estimate the transmission line parameters of each span of a multi-span transmission system, such as a chromatic dispersion coefficient and a nonlinear constant, based on a received signal at the receiving end of the transmission line. Furthermore, in a multi-span transmission system, it becomes possible to easily estimate the transmission line parameters of each span of multiple spans only at the receiving end of the transmission line, without adding new optical components or devices such as an optical spectrum analyzer.

[0152] For example, in the transmission path parameter estimation device according to the embodiment, when the first transmission path has known transmission path parameters, the control unit stores in the storage unit a nonlinear phase rotation amount distribution calculated using time waveform data of the known transmission path parameters, and can obtain an unknown nonlinear constant of the second transmission path by referring to the data in the storage unit. The control unit can also collect signal strength information of digital coherent light transmitted through the second transmission path, and estimate the nonlinear constant of each span of the second transmission path based on the collected signal strength information and the data stored in the storage unit. The control unit may also include a reference value calculation unit that calculates the nonlinear phase rotation amount distribution based on a transmission simulation or known transmission conditions in a measurement system.

[0153] Furthermore, the transmission path parameter estimation device according to the embodiment may be configured to store in advance in a storage unit a first chromatic dispersion coefficient, a first nonlinear constant, an input power at a first fiber input section, and a first nonlinear phase rotation amount at a first fiber input section, which are known in a first transmission path. The control unit may include a nonlinear phase rotation estimation unit that estimates a nonlinear phase rotation distribution at each point of the second transmission line as a function of an accumulated chromatic dispersion amount from the transmitting end based on signal strength information of signal light collected from an optical receiving unit of digital coherent light transmitted through a second transmission line different from the first transmission line; a span detection unit that detects the chromatic dispersion amount of each span based on the nonlinear phase rotation distribution; a chromatic dispersion coefficient estimation unit that calculates a second chromatic dispersion coefficient of each span from information on the fiber length of each span and the chromatic dispersion amount of each span; a detection unit that detects the amount of nonlinear phase rotation at the second fiber input unit of each span; and a nonlinear constant estimation unit that calculates a nonlinear constant of each span of the second transmission line based on information on the first chromatic dispersion coefficient, the first nonlinear constant, the input power at the first fiber input, the first nonlinear phase rotation amount at the first fiber input unit, the second chromatic dispersion coefficient, the nonlinear phase rotation amount at the second fiber input unit, and the fiber input power of each span. In this case, for example, the information on the fiber length of each span can be acquired by the administrator through operational input of the transmission line design information, etc. In this way, each parameter of the reference value is calculated in advance based on the known transmission conditions stored in the storage unit, and the control unit can refer to it to easily estimate the transmission line parameters of the span to be estimated.

[0154] Furthermore, the transmission path parameter estimation device according to the embodiment may store in advance in a storage unit a first nonlinear constant in a known first transmission path, an input power at a first fiber input unit, an amount of first nonlinear phase rotation at the first fiber input unit, and a slope of the amount of first nonlinear phase rotation with respect to the amount of chromatic dispersion. The control unit may include a nonlinear phase rotation amount estimating unit that estimates the nonlinear phase rotation amount distribution at each point of the second transmission line as a function of the accumulated chromatic dispersion amount from the transmitting end based on the signal strength information of the signal light collected from the optical receiving unit of the digital coherent light transmitted through the second transmission line different from the first transmission line, a detecting unit that detects the nonlinear phase rotation amount at the second fiber input unit of each span, a calculating unit that calculates the slope of the second nonlinear phase rotation amount with respect to the chromatic dispersion amount of each span, and a nonlinear constant estimating unit that calculates the nonlinear constant of each span of the second transmission line based on the first nonlinear constant, the input power at the first fiber input unit, the first nonlinear phase rotation amount at the first fiber input unit, the slope of the first nonlinear phase rotation amount, the nonlinear phase rotation amount at the second fiber input unit, the slope of the second nonlinear phase rotation amount, and the fiber input power information of each span. In this way, each parameter of the reference value is calculated in advance based on the known transmission conditions stored in the storage unit, and the control unit can easily estimate the transmission line parameters of the estimation target span by referring to the calculated parameters.

[0155] In addition, in the transmission channel parameter estimation device according to the embodiment, the control unit may output the estimated nonlinear constant as an input parameter of a transmission channel model that simulates the second transmission channel. This makes it possible to construct a transmission channel model that reflects the actual state of the transmission channel, thereby improving the estimation accuracy in transmission simulation, QoT estimation, etc.

[0156] In addition, the control unit of the transmission line parameter estimation device of the embodiment may include a threshold determination unit that compares the estimated nonlinear constant with a threshold value that is predetermined based on fiber information for each fiber type of the second transmission line, and identifies the fiber type of the span to be estimated. This makes it possible to easily identify the fiber type of the span to be estimated. In particular, in fiber type identification based on power profile estimation of the existing technology, the calculated chromatic dispersion coefficient alone is not enough to identify the fiber type based on the existing fiber specifications, and it is necessary to transmit signal light of multiple wavelengths to the transmission line and calculate the power profile, which increases calculation costs and makes the process complicated. In contrast, according to the embodiment, the fiber type of each span of the transmission line can be estimated with one wavelength, which reduces the number of wavelengths and reduces calculation costs. In addition, it becomes possible to efficiently estimate the fiber type installed in each span of the transmission line. In addition, it becomes possible to prevent the influence of performance degradation such as a decrease in SNR margin due to incorrect fiber connection.

[0157] In addition, in the transmission path parameter estimation device according to the embodiment, the control unit may include a fiber type determination unit that, when a span whose fiber type can be identified is present among the multiple spans of the second transmission path, calculates the fiber type and nonlinear constant of the span. In this way, the reference value is not limited to being calculated, and when a span whose fiber type can be identified is present among the multiple spans of the transmission path, information on the fiber type of the span may be used.

[0158] In the transmission path parameter estimation device according to the embodiment, the control unit may include a span information vector creation unit that creates a span information vector in which the estimated chromatic dispersion coefficients and nonlinear constants of each span are arranged for all spans, and an evaluation unit that identifies a combination of fiber types for each span based on a vector distance between the chromatic dispersion coefficients and nonlinear constants of fiber types previously narrowed down as candidates. This makes it possible to identify the fiber type of each span from the patterns of chromatic dispersion coefficients and nonlinear constants for each combination of fiber types in a plurality of spans.

[0159] In addition, in the transmission path parameter estimation device according to the embodiment, the span information vector creation unit may extract spans whose fiber types are not yet identified and create a span information vector. This makes it possible to simplify the identification process by reducing the number of combination patterns using the fiber types of each of a plurality of spans.

[0160] The following supplementary notes are further disclosed regarding the above-described embodiment.

[0161] (Appendix 1) A nonlinear phase rotation distribution calculated using time waveform data acquired from a receiver of a first transmission line; A storage unit that stores in advance an amount of nonlinear phase rotation in a second transmission path different from the first transmission path; a control unit that refers to the data in the storage unit and determines a nonlinear constant of each span of the second transmission line based on a distribution of the amount of nonlinear phase rotation; A transmission path parameter estimation device comprising:

[0162] (Supplementary Note 2) The first transmission path has known transmission path parameters; The control unit is storing the nonlinear phase rotation amount distribution calculated using the time waveform data of the known transmission path parameters in the storage unit; determining the unknown nonlinear constant of the second transmission line by referring to the data in the storage unit; 2. The transmission channel parameter estimation device according to claim 1,

[0163] (Additional Note 3) The control unit is collecting signal strength information of the digital coherent light transmitted through the second transmission path, and estimating a nonlinear constant of each span of the second transmission path based on the collected signal strength information and the data stored in the storage unit; 2. The transmission channel parameter estimation device according to claim 1,

[0164] (Additional Note 4) The control unit is A reference value calculation unit that calculates the nonlinear phase rotation amount distribution based on a transmission simulation or a known transmission condition in a measurement system. 2. The transmission channel parameter estimation device according to claim 1,

[0165] (Additional Note 5) The storage unit is storing in advance a first chromatic dispersion coefficient, a first nonlinear constant, an input power at a first fiber input section, and a first nonlinear phase rotation amount at the first fiber input section in a known first transmission path; The control unit is a nonlinear phase rotation amount estimating unit that estimates a nonlinear phase rotation amount distribution at each point of the second transmission path as a function of an accumulated chromatic dispersion amount from a transmitting end based on signal intensity information of a signal light collected from an optical receiving unit of a digital coherent light transmitted through a second transmission path different from the first transmission path; a span detector for detecting the amount of chromatic dispersion of each span based on the nonlinear phase rotation amount distribution; a chromatic dispersion coefficient estimating unit that calculates a second chromatic dispersion coefficient of each span from information on the fiber length of each span and the chromatic dispersion amount of each span; a detector for detecting an amount of nonlinear phase rotation at a second fiber input portion of each of the spans; a nonlinear constant estimating unit that calculates a nonlinear constant of each span of the second transmission line based on information on the first chromatic dispersion coefficient, the first nonlinear constant, the input power at the first fiber input, the first nonlinear phase rotation amount at the first fiber input section, the second chromatic dispersion coefficient, the nonlinear phase rotation amount at the second fiber input section, and the fiber input power of each span; 2. A channel parameter estimation device according to claim 1, comprising:

[0166] (Additional Note 6) The control unit is acquiring information on the fiber length of each of the spans from design information of the transmission line; 6. The transmission channel parameter estimation device according to claim 5,

[0167] (Additional Note 7) The storage unit is storing in advance a first nonlinear constant, an input power at a first fiber input section, a first nonlinear phase rotation amount at the first fiber input section, and a slope of the first nonlinear phase rotation amount with respect to the chromatic dispersion amount in a known first transmission path; The control unit is a nonlinear phase rotation amount estimating unit that estimates a nonlinear phase rotation amount distribution at each point of the second transmission path as a function of an accumulated chromatic dispersion amount from a transmitting end based on signal intensity information of a signal light collected from an optical receiving unit of a digital coherent light transmitted through a second transmission path different from the first transmission path; a detector for detecting an amount of nonlinear phase rotation at a second fiber input portion of each of the spans; A calculation unit that calculates a slope of a second nonlinear phase rotation amount with respect to the chromatic dispersion amount of each of the spans; a nonlinear constant estimating unit that calculates a nonlinear constant of each span of the second transmission line based on the first nonlinear constant, the input power at the first fiber input section, the first amount of nonlinear phase rotation at the first fiber input section, a slope of the first amount of nonlinear phase rotation, the amount of nonlinear phase rotation at the second fiber input section, a slope of the second amount of nonlinear phase rotation, and information on the fiber input power of each span; 2. A channel parameter estimation device according to claim 1, comprising:

[0168] (Additional Note 8) The control unit is 2. The transmission channel parameter estimation device according to claim 1, wherein the estimated nonlinear constant is output as an input parameter of a transmission channel model that simulates the second transmission channel.

[0169] (Additional Note 9) The control unit is a threshold determination unit that compares the estimated nonlinear constant with a predetermined threshold based on fiber information for each fiber type of the second transmission line, and identifies a fiber type of the span to be estimated; 2. The transmission channel parameter estimation device according to claim 1,

[0170] (Additional Note 10) The control unit is 2. The transmission path parameter estimation device according to claim 1, further comprising a fiber type determination unit that, when a span whose fiber type can be identified is present among the multiple spans of the second transmission path, calculates a fiber type and a nonlinear coefficient of the span.

[0171] (Additional Note 11) The control unit is a span information vector creation unit that creates a span information vector in which the estimated chromatic dispersion coefficient and the nonlinear constant of each span are arranged for all spans; and an evaluation unit that identifies a combination of fiber types for each span based on a vector distance between the chromatic dispersion coefficient and the nonlinear constant of fiber types previously narrowed down as candidates.

[0172] (Appendix 12) A nonlinear phase rotation amount distribution obtained using time waveform data acquired from a receiver of a first transmission line; A nonlinear phase rotation amount in a second transmission path different from the first transmission path is recorded in advance. Store in memory, The data in the storage unit is referred to, and based on the distribution of the amount of nonlinear phase rotation, the second transmission line Obtain the nonlinear coefficient for each span. 4. A transmission path parameter estimation method comprising: [Explanation of symbols]

[0173] 100 Transmission line parameter estimation device 111 Nonlinear phase rotation amount estimator 112 Span detector 113 Reference value acquisition unit 114 Chromatic dispersion coefficient estimation unit 115 Nonlinear constant estimation section 120 Transmission Line 130,1030 Optical receiver 131 Digital coherent receiving processing unit 132 Digital signal processing section 501 Processor 502 Memory 505 Recording media 1001 Transmission signal generator 1002 Optical Fiber Transmission Calculation Department 1010 Reference value calculation unit 1011 Nonlinear phase rotation amount estimator 1012 Span detector 1013 Reference value extraction unit 1031 Digital coherent reception processing calculation unit 1032 Digital Signal Processing Calculation Unit 1301 Optical transmitter (Tx) 1302 MUX 1303 Optical Amplifier 1304 DEMUX 1305 Optical Receiver (Rx) 1310 Transmission Line Model 1501 Threshold judgment unit 1701 Fiber type determination unit 2401 Span Information Vector Creation Unit 2402 Evaluation Department NW Network

Claims

1. A nonlinear phase rotation distribution calculated using time waveform data acquired from a receiver of the first transmission line; a storage unit that stores in advance an amount of nonlinear phase rotation in a second transmission path different from the first transmission path; a control unit that refers to the data in the storage unit and determines a nonlinear constant of each span of the second transmission line based on a distribution of the amount of nonlinear phase rotation; A transmission path parameter estimation device comprising:

2. the first transmission path has known transmission path parameters; The control unit is storing the nonlinear phase rotation amount distribution calculated using the time waveform data of the known transmission path parameters in the storage unit; determining the unknown nonlinear constant of the second transmission line by referring to the data in the storage unit; 2. The transmission path parameter estimation device according to claim 1 .

3. The control unit is collecting signal strength information of the digital coherent light transmitted through the second transmission path, and estimating a nonlinear constant of each span of the second transmission path based on the collected signal strength information and the data stored in the storage unit; 2. The transmission path parameter estimation device according to claim 1 .

4. The control unit is A reference value calculation unit that calculates the nonlinear phase rotation amount distribution based on a transmission simulation or a known transmission condition in a measurement system.

2. The transmission path parameter estimation device according to claim 1 .

5. The storage unit is storing in advance a first chromatic dispersion coefficient, a first nonlinear constant, an input power at a first fiber input section, and a first nonlinear phase rotation amount at the first fiber input section in a known first transmission path; The control unit is a nonlinear phase rotation amount estimating unit that estimates a nonlinear phase rotation amount distribution at each point of the second transmission path as a function of an accumulated chromatic dispersion amount from a transmitting end based on signal intensity information of a signal light collected from an optical receiving unit of a digital coherent light transmitted through a second transmission path different from the first transmission path; a span detector for detecting the amount of chromatic dispersion of each span based on the nonlinear phase rotation amount distribution; a chromatic dispersion coefficient estimating unit that calculates a second chromatic dispersion coefficient of each span from information on the fiber length of each span and the chromatic dispersion amount of each span; a detector for detecting an amount of nonlinear phase rotation at a second fiber input portion of each of the spans; a nonlinear constant estimating unit that calculates a nonlinear constant of each span of the second transmission line based on information on the first chromatic dispersion coefficient, the first nonlinear constant, the input power at the first fiber input, the first nonlinear phase rotation amount at the first fiber input section, the second chromatic dispersion coefficient, the nonlinear phase rotation amount at the second fiber input section, and the fiber input power of each span; 2. The transmission path parameter estimation device according to claim 1, further comprising:

6. The control unit is acquiring information on the fiber length of each of the spans from design information of the transmission line; 6. The transmission path parameter estimation device according to claim 5.

7. The storage unit is storing in advance a first nonlinear constant, an input power at a first fiber input section, a first nonlinear phase rotation amount at the first fiber input section, and a slope of the first nonlinear phase rotation amount with respect to the chromatic dispersion amount in a known first transmission path; The control unit is a nonlinear phase rotation amount estimating unit that estimates a nonlinear phase rotation amount distribution at each point of the second transmission path as a function of an accumulated chromatic dispersion amount from a transmitting end based on signal intensity information of a signal light collected from an optical receiving unit of a digital coherent light transmitted through a second transmission path different from the first transmission path; a detector for detecting an amount of nonlinear phase rotation at a second fiber input portion of each of the spans; a calculation unit that calculates a slope of a second nonlinear phase rotation amount with respect to a chromatic dispersion amount of each of the spans; a nonlinear constant estimating unit that calculates a nonlinear constant of each span of the second transmission line based on the first nonlinear constant, the input power at the first fiber input section, the first amount of nonlinear phase rotation at the first fiber input section, a slope of the first amount of nonlinear phase rotation, the amount of nonlinear phase rotation at the second fiber input section, a slope of the second amount of nonlinear phase rotation, and information on the fiber input power of each span; 2. The transmission path parameter estimation device according to claim 1, further comprising:

8. The control unit is 2. The transmission path parameter estimation device according to claim 1, wherein the estimated nonlinear constant is output as an input parameter of a transmission path model that simulates the second transmission path.

9. The control unit is a threshold determination unit that compares the estimated nonlinear constant with a predetermined threshold based on fiber information for each fiber type of the second transmission line, and identifies a fiber type of the span to be estimated; 2. The transmission path parameter estimation device according to claim 1 .

10. The control unit is a span information vector creation unit that creates a span information vector in which the estimated chromatic dispersion coefficient and the nonlinear constant of each span are arranged for all spans; 2. The transmission line parameter estimation device according to claim 1, further comprising: an evaluation unit that identifies a combination of fiber types for each span based on a vector distance between the chromatic dispersion coefficient and the nonlinear constant of fiber types previously narrowed down as candidates.

11. A nonlinear phase rotation distribution calculated using time waveform data acquired from a receiver of the first transmission line; a nonlinear phase rotation amount in a second transmission path different from the first transmission path is stored in a storage unit in advance; determining a nonlinear constant for each span of the second transmission line based on a distribution of the amount of nonlinear phase rotation by referring to the data in the storage unit; 4. A transmission path parameter estimation method comprising:

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