Network Controller, Estimation Method, and Computer Program

Abstract

This network controller is provided to an optical transmission system in which an optical transmitter and an optical receiver communicate via an optical transmission line, the network controller comprising: a simulation unit that constructs a plurality of simulation models by virtually reproducing, in different virtual spaces, the state of the optical transmission line in the optical transmission system including the optical transmitter, the optical receiver, and the optical transmission line, and that estimates characteristics of a device provided to the optical transmission line for each simulation model; and an ideal output estimation unit that estimates, on the basis of the device characteristics estimated by the simulation unit and the characteristics of the device provided to the optical transmission line obtained in a real space, the ideal device characteristic output. The state of the optical transmission line in the optical transmission system differs for each simulation model.

Description

Technical Field

[0001] The present invention relates to a network controller, an estimation method, and a computer program.

Background Art

[0002] Optical transmission systems incorporate various devices such as optical fibers, optical amplifiers, and optical filters. Conventionally, the characteristics of these devices have been measured using analog measuring instruments such as an OTDR (Optical Time Domain Reflectometer) and an optical spectrum analyzer. However, measurement using an analog measuring instrument requires a measuring instrument for each optical node and optical fiber, resulting in increased equipment costs and operating costs.

[0003] Therefore, in recent years, a technique has been proposed to extract the characteristics of various devices in an optical transmission system by digital signal processing on the receiving side instead of measurement using an analog measuring instrument (see, for example, Non-Patent Documents 1 to 4). In the techniques described in Non-Patent Documents 1 to 4, it is possible to estimate the responses of various devices in the transmission system only by digital signal processing on the received signal of the optical transmission system. For example, in the techniques described in Non-Patent Documents 1 to 4, it is possible to estimate optical fiber loss or dispersion distribution, optical amplifier gain spectrum, optical filter response, etc.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Non-Patent Document 2

[0005] However, although the techniques described in Non-Patent Documents 1 to 4 can be measured more simply than analog measuring instruments, there is a problem that the estimation accuracy and resolution of the characteristics of the device are inferior.

[0006] In view of the above circumstances, an object of the present invention is to provide a technique capable of accurately estimating the characteristics of a device constituting an optical transmission system. [Means for Solving the Problems]

[0007] One aspect of the present invention is a network controller provided in an optical transmission system in which an optical transmitter and an optical receiver communicate via an optical transmission line, the network controller constructing a plurality of simulation models by virtually reproducing the state of the optical transmission line in the optical transmission system including the optical transmitter, the optical receiver, and the optical transmission line in different virtual spaces, and estimating the characteristics of the devices provided on the optical transmission line for each simulation model, and an ideal output estimation unit that estimates an output of the characteristics of an ideal device based on the characteristics of the devices estimated by the simulation unit and the characteristics of the devices provided on the optical transmission line obtained in the real space, wherein the state of the optical transmission line in the optical transmission system is a different network controller for each simulation model.

[0008] One aspect of the present invention is an estimation method performed by a network controller provided in an optical transmission system in which an optical transmitter and an optical receiver communicate via an optical transmission line, the method constructing a plurality of simulation models by virtually reproducing the state of the optical transmission line in the optical transmission system including the optical transmitter, the optical receiver, and the optical transmission line in different virtual spaces, estimating the characteristics of the devices provided on the optical transmission line for each simulation model, estimating an output of the characteristics of an ideal device based on the estimated characteristics of the devices and the characteristics of the devices provided on the optical transmission line obtained in the real space, and wherein the state of the optical transmission line in the optical transmission system is different for each simulation model.

[0009] One aspect of the present invention is a computer program for causing a computer to function as the above network controller.

Effects of the Invention

[0010] According to the present invention, it is possible to accurately estimate the characteristics of the devices constituting the optical transmission system.

Brief Description of the Drawings

[0011]

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Embodiments for Carrying Out the Invention

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. (First Embodiment) FIG. 1 is a diagram for explaining the outline of the optical transmission system in the first embodiment. In the first embodiment, a digital filter is used as a method for improving the estimation accuracy of the characteristics of the devices constituting the optical transmission system. In the following description, as an example of the characteristics of the device, the loss distribution of the optical fiber will be described, but the same method is applicable to the dispersion distribution of the optical fiber, the amplifier gain spectrum, and the optical filter response. In the following description, the techniques described in Non - Patent Documents 1 to 4 are referred to as DLM (Digital longitudinal monitoring).

[0013] In order to improve the estimation accuracy of the characteristics of the device, it is conceivable to design a digital filter that converts the output obtained by the DLM (hereinafter referred to as the "DLM output") into an ideal output. However, in order to configure a filter that accurately outputs the characteristics of all transmission line devices, it is necessary to actually prepare all optical transmission lines and prepare a huge amount of data sets of transmission line device characteristics (a set of DLM output and ideal output), which is not realistic.

[0014] Therefore, in the first embodiment, in order to eliminate the lack of data sets for configuring the digital filter, as shown in the lower figure of FIG. 1, a simulation model of the optical transmission system (digital twin of the optical transmission line) is constructed. Note that optical transmission line models have been extensively studied, and for example, the technology of the following Reference 1 can be used. For the optical filter model, an arbitrary filter shape can be used according to the optical filter to be used. For example, a Gaussian filter may be used. (Reference 1: E. Ip et al., “Compensation of Dispersion and Nonlinear Impairments Using Digital Backpropagation”, J. Lightw. Technol., 26(20),2008)

[0015] In the first embodiment, like an actual optical transmission system, all states of the optical transmission line (loss amount, loss position, dispersion amount, etc.) are virtually reproduced on the digital twin to obtain the DLM output, and a plurality of data sets of the DLM output and the ideal output are held. Here, the ideal output refers to the loss distribution of the optical fiber given by the user on the digital twin (in the case where the estimation target of the DLM is the dispersion distribution of the optical fiber, the amplifier gain spectrum, the optical filter response, etc., those), and the state of the transmission line that is the estimation target of the DLM. Then, by constructing a digital filter based on the plurality of held data sets, the above-mentioned lack of data sets is eliminated. As a result, a digital filter that accurately outputs the characteristics of the device can be constructed. Hereinafter, the specific configuration will be described.

[0016] FIG. 2 is a diagram showing the configuration of the optical transmission system 100 in the first embodiment. The optical transmission system 100 includes an optical transmitter 1, an optical receiver 2, an optical transmission line 3, and a network controller 6. The optical transmitter 1 and the optical receiver 2 are communicably connected via the optical transmission line 3. The optical transmission line 3 is composed of, for example, an optical fiber F. One or more relay nodes 31A that amplify and relay an optical signal attenuating during propagation are inserted as optical amplifiers (hereinafter also referred to as "optical amps") in the middle of the transmission line in the optical transmission line 3. Note that an optical filter may be provided in the optical transmission line 3.

[0017] The optical transmitter 1 encodes transmission information given from an external information source to generate an electrical signal, converts the generated electrical signal into an optical signal, and transmits the optical signal to the optical receiver 2 via the optical transmission line 3.

[0018] The optical receiver 2 includes a coherent receiver 21 and a digital signal processing unit 22. The coherent receiver 21 separates a baseband optical signal into two optical signals whose polarization planes are orthogonal. These optical signals and the local light emission of a local light source (not shown) are input to a 90° hybrid circuit (not shown), and a total of four output lights, namely, a set of output lights obtained by interfering both lights in phase and antiphase with each other, and a set of output lights obtained by interfering orthogonally (90°) and anti-orthogonally (-90°), are obtained. These output lights are respectively converted into analog signals by photodiodes (not shown). The coherent receiver 21 converts these analog signals into digital signals.

[0019] When an optical signal propagates through the optical transmission line 3, the signal waveform is distorted by a non-linear optical effect in which the phase of the signal rotates in proportion to the optical power of the signal. The digital signal processing unit 22 takes in the digital signal output from the coherent receiver 21 as a received signal, and performs non-linear optical compensation on the received signal taken in.

[0020] The digital signal processing unit 22 estimates the characteristics of the devices in the optical transmission line 3 based on the received optical signal and notifies the network controller 6 as the DLM output. For example, the digital signal processing unit 22 generates a signal power profile indicating the intensity distribution of the optical signal in the propagation direction as the DLM output. The digital signal processing unit 22 supplies the generated DLM output to the network controller 6.

[0021] The network controller 6 constructs a plurality of simulation models including the optical transmitter 1, the optical receiver 2, and the optical transmission line 3 that constitute the real-space optical transmission system. At this time, the network controller 6 constructs a plurality of simulation models by virtually reproducing the states (loss amount, loss position, dispersion amount, etc.) of all optical transmission lines in different virtual spaces. The network controller 6 estimates the ideal DLM output based on a data set including the virtual DLM output obtained by each of the constructed simulation models and the ideal output corresponding to the virtual DLM output, and the DLM output obtained from the optical receiver 2.

[0022] FIG. 3 is a diagram showing an example of the functional configuration of the digital signal processing unit 22 in the first embodiment. The digital signal processing unit 22 includes a non-linear optical compensation unit 23, an adaptive equalization unit 24, a frequency offset compensation unit 25, a carrier phase noise compensation unit 26, a coefficient update unit 27, and a transmission characteristic estimation unit 28.

[0023] FIG. 4 is a schematic block diagram showing the functional configuration of the non-linear optical compensation unit 23 in the first embodiment. The non-linear optical compensation unit 23 includes a plurality of linear compensation units 231-1 to 231-N and a plurality of non-linear compensation units 232-1 to 232-N. One linear compensation unit 231 and one non-linear compensation unit 232 form one set for performing linear compensation and non-linear compensation, and the non-linear optical compensation unit 23 includes N sets for performing the processing by this set in N steps.

[0024] The linear compensation unit 231-1 includes a Fourier transform unit 233-1, a wavelength dispersion compensation unit 234-1, and an inverse Fourier transform unit 235-1. The Fourier transform unit 233-1 converts the received signal in the time domain into a received signal in the frequency domain by performing an FFT on the received signal in the time domain.

[0025] The wavelength dispersion compensation unit 234-1 performs wavelength dispersion compensation on the received signal in the frequency domain by multiplying it by a predetermined value (for example, exp^(-jβ k ω2)). Note that the symbol "^" means that the value after "^" is the superscript of exp. For example, in the case of exp^(-jβ k ω2), it means that (-jβ k ω2) is the superscript of exp. The same applies to the explanation of "^" hereinafter. The wavelength dispersion compensation unit 234-1 performs wavelength dispersion compensation using the dispersion coefficient β k set as an initial value at the start of processing, and performs wavelength dispersion compensation using the updated dispersion coefficient β k each time the dispersion coefficient β k is updated by the coefficient update unit 27.

[0026] The inverse Fourier transform unit 235-1 converts the wavelength dispersion compensated received signal into a received signal in the time domain by performing an IFFT on the signal output from the wavelength dispersion compensation unit 234-1. The non-linear optical compensation unit 23 compensates for the non-linear optical effect by multiplying the signal sequence output from the inverse Fourier transform unit 235 by a predetermined value (for example, exp^(-jφ k )). Specifically, the non-linear optical compensation unit 23 compensates for the non-linear optical effect using the phase rotation amount φ k set as an initial value at the start of processing, and compensates for the non-linear optical effect using the updated phase rotation amount φ k each time the phase rotation amount φ k is updated by the coefficient update unit 27.

[0027] The linear compensation unit 231-N performs the same processing as the linear compensation unit 231-1. Also, the non-linear compensation unit 232-N performs the same processing as the non-linear compensation unit 232-1.

[0028] Returning to FIG. 3, the description of the optical receiver 2 will be continued. The adaptive equalization unit 24 is a functional unit that compensates for the distortion generated in the waveform of the optical signal in the optical transmission line 3. That is, the adaptive equalization unit 24 is a functional unit that corrects the symbol errors generated in the optical signal due to inter-symbol interference in the optical transmission line 3. The adaptive equalization unit 24 executes adaptive equalization processing by a FIR filter (finite impulse response filter) according to the set tap coefficients.

[0029] The frequency offset compensation unit 25 executes a process of compensating for the frequency offset with respect to the four digital signals for which the adaptive equalization processing has been executed.

[0030] The carrier phase noise compensation unit 26 executes a process of compensating for the phase offset with respect to the four digital signals for which the frequency offset has been compensated.

[0031] The coefficient update unit 27 updates all the coefficients (for example, the dispersion coefficient β k , the phase rotation amount φ k etc.) used in the non-linear optical compensation unit 23 in all steps. In the first embodiment, for example, the coefficient update unit 27 updates all the coefficients (for example, the dispersion coefficient β k , the phase rotation amount φ k etc.) used in the non-linear optical compensation unit 23 in all steps based on the output signal from the carrier phase noise compensation unit 26 and the training signal. The coefficient update unit 27 sets the updated coefficients to each functional unit of the non-linear optical compensation unit 23. The training signal compared with the output signal in the first embodiment is the transmission signal converted into an electrical signal.

[0032] The transmission characteristic estimation unit 28 estimates the transmission characteristics of the optical transmission line 3. For example, the transmission characteristic estimation unit 28 estimates the optimized phase rotation amount φ kEstimate the loss distribution using it. The transmission characteristic estimation unit 28 supplies information indicating the estimated loss distribution to the network controller 6 as the DLM output. Note that the transmission characteristic estimation unit 28 may estimate the dispersion distribution using the optimized dispersion coefficient β k In this case, the transmission characteristic estimation unit 28 supplies information indicating the dispersion distribution to the network controller 6 as the DLM output.

[0033] Next, returning to FIG. 2, the specific configuration of the network controller 6 will be described. The network controller 6 includes a simulation unit 61, a storage unit 62, and an ideal output estimation unit 63.

[0034] The simulation unit 61 constructs one or more simulation models for virtually reproducing the states (loss amount, loss position, dispersion amount, etc.) of all the optical transmission paths 3 in the optical transmission system 100. The simulation unit 61 obtains one or more virtual DLM outputs and ideal outputs corresponding to the one or more virtual DLM outputs respectively by each of the one or more constructed simulation models.

[0035] The storage unit 62 stores one or more first data sets in which one or more virtual DLM outputs obtained by the simulation unit 61 and ideal outputs corresponding to the one or more virtual DLM outputs are associated. Further, the storage unit 62 stores one or more second data sets in which one or more DLM outputs obtained in the actual environment and ideal outputs corresponding to the one or more DLM outputs are associated. The ideal output may be manually associated or automatically associated by the simulation unit 61. The storage unit 62 is configured using a storage device such as a magnetic storage device or a semiconductor storage device.

[0036] The ideal output estimation unit 63 is composed of a filter construction unit 631 and an ideal output unit 632. The filter construction unit 631 constructs a digital filter using the first data set and the second data set stored in the storage unit 62. The ideal output unit 632 estimates the output of the characteristics of the ideal device of the optical transmission system 100 based on the digital filter constructed by the filter construction unit 631 and the DLM output obtained from the optical receiver 2.

[0037] FIG. 5 is a flowchart showing the processing flow of the network controller 6 in the first embodiment. It is assumed that the simulation result obtained by the simulation unit 61 is stored in the storage unit 62 at the start of the processing in FIG. 5. The filter construction unit 631 constructs a digital filter using the first data set and the second data set stored in the storage unit 62 (step S101). Specifically, the filter construction unit 631 mixes the first data set and the second data set at an arbitrary ratio, and constructs an optimal FIR filter h that minimizes the mean square error ||y - Ah|| based on, for example, Equation (2) obtained by transforming Equation (1) below. 2

[0038]

Equation

[0039]

Equation

[0040] Note that the digital filter used here is arbitrary. In the above example, a configuration for constructing a linear filter such as an FIR filter is shown, but a non-linear filter such as a Volterra filter or a neural network may also be used. Using a non-linear filter such as a Volterra filter or a neural network may improve the expressive power of the filter and make it possible to construct a more accurate filter.

[0041] ​Note that the method for constructing the digital filter is also arbitrary. An optimal filter using the least squares method as in the above example may be used, or a filter optimized using the gradient method may be used. The objective function in the gradient method may also use something other than the squared error. For example, A in Equation (2) T An arbitrary regularization term λR may be added to A. R is an arbitrary matrix.

[0042] After the digital filter is constructed, the user of the optical transmission system 100 starts communication between the optical transmitter 1 and the optical receiver 2. As a result, at the optical receiver 2, a DLM output can be obtained by performing digital signal processing on the optical signal transmitted from the optical transmitter 1. The optical receiver 2 outputs the obtained DLM output to the network controller 6. The ideal output unit 632 of the network controller 6 takes the DLM output obtained by the optical receiver 2 as an input (step S102).

[0043] The ideal output unit 632 estimates the output of the characteristics of the ideal device by inputting the input DLM output into the digital filter constructed by the filter construction unit 631 (step S103). For example, when the digital filter is a high-precision filter, noise is removed from the input DLM output, and an output result in which the characteristics of the device are more clearly shown can be obtained. The ideal output unit 632 outputs the information of the estimated output of the characteristics of the ideal device to the outside.

[0044] According to the optical transmission system 100 configured as described above, a plurality of simulation models are constructed by virtually reproducing the states of a plurality of optical transmission paths in the optical transmission system 100 including the optical transmitter 1, the optical receiver 2, and the optical transmission path 3 in different virtual spaces, and a simulation unit 61 that estimates the characteristics of the devices provided in the optical transmission path 3 for each simulation model, and an ideal output estimation unit 63 that estimates the output of the characteristics of an ideal device based on the characteristics of the devices estimated by the simulation unit 61 and the characteristics of the devices provided in the optical transmission path 3 obtained in the real space. Thereby, it is possible to estimate the output of the characteristics of an ideal device in consideration of the states of all optical transmission paths. Therefore, it becomes possible to accurately estimate the characteristics of the devices constituting the transmission system.

[0045] Furthermore, in the optical transmission system 100, the characteristics of all transmission path devices are estimated by the simulation by the simulation unit 61. And in the optical transmission system 100, a digital filter is constructed using the first data set and the second data set, and the output of the characteristics of the devices provided in the optical transmission path obtained in the real space is input to the constructed digital filter, thereby estimating the output of the characteristics of an ideal device. As described above, in order to improve the estimation accuracy of the characteristics of the devices, it is necessary to configure a filter that accurately outputs the characteristics of all transmission path devices. It is not realistic to actually prepare all optical transmission paths and prepare a huge amount of data sets of the transmission path device characteristics. On the other hand, in the present invention, since the characteristics of all transmission path devices are estimated by simulation, more data sets can be prepared. As a result, a digital filter that accurately outputs the characteristics of the devices can be constructed. Therefore, in the optical transmission system 100, by using the constructed digital filter, it becomes possible to accurately estimate the characteristics of the devices constituting the optical transmission system.

[0046] (Second Embodiment) In the second embodiment, as a method for improving the estimation accuracy of the characteristics of the devices constituting the optical transmission system, the maximum likelihood estimation method is used.

[0047] FIG. 6 is a diagram for explaining the outline of the optical transmission system in the second embodiment. Also in the second embodiment, similar to the first embodiment, the state (loss amount, loss position, dispersion amount, etc.) of all optical transmission paths is virtually reproduced on the digital twin to obtain the DLM output, and a plurality of data sets of the DLM output and the ideal output are held. Then, in the network controller, the likelihoods of the plurality of held DLM outputs and the actually obtained DLM output are calculated respectively, and the DLM output that gives the maximum likelihood is specified. The state (ideal output) of the optical transmission path that output the specified DLM output becomes the state of the transmission path to be obtained. Hereinafter, the specific configuration will be described.

[0048] FIG. 7 is a diagram showing the configuration of the optical transmission system 100a in the second embodiment. The optical transmission system 100a includes an optical transmitter 1, an optical receiver 2, an optical transmission path 3, and a network controller 6a. The optical transmission system 100a is the same as the optical transmission system 100 except for the configuration of the network controller 6a. Therefore, the differences from the first embodiment will be described.

[0049] The network controller 6a includes a simulation unit 61, a storage unit 62a, and an ideal output estimation unit 63a.

[0050] The storage unit 62a stores one or more virtual DLM outputs obtained by the simulation unit 61 and the ideal outputs corresponding to the one or more virtual DLM outputs respectively. The storage unit 62a is configured using a storage device such as a magnetic storage device or a semiconductor storage device.

[0051] The ideal output estimation unit 63a is composed of a likelihood calculation unit 633 and an ideal output unit 632a. The likelihood calculation unit 633 calculates the likelihood of each of one or more virtual DLM outputs and the DLM output obtained from the optical receiver 2. The ideal output unit 632a identifies the virtual DLM output that gives the maximum likelihood among the plurality of likelihoods calculated by the likelihood calculation unit 633. The ideal output unit 632a estimates the state (ideal output) of the optical transmission path corresponding to the identified virtual DLM output as the output of the ideal characteristics of the devices in the optical transmission system 100a.

[0052] FIG. 8 is a flowchart showing the processing flow of the network controller 6a in the second embodiment. It is assumed that at the start of the processing in FIG. 8, the simulation results obtained by the simulation unit 61 are stored in the storage unit 62. The likelihood calculation unit 633 takes the DLM output obtained by the optical receiver 2 as an input (step S201). The likelihood calculation unit 633 calculates the likelihood of the input DLM output and each of the virtual DLM outputs stored in the storage unit 62a (step S202). For example, the likelihood calculation unit 633 may calculate the likelihood of the input DLM output and each of the virtual DLM outputs stored in the storage unit 62a based on the following formula (3).

[0053]

Equation

[0054] In formula (3), a represents the DLM output and a' represents the virtual DLM output. Note that the likelihood calculation unit 633 may calculate the likelihood by a method other than the squared error (with a negative sign) shown in formula (3).

[0055] The likelihood calculation unit 633 outputs the information of each calculated likelihood to the ideal output unit 632a. The ideal output unit 632a identifies a virtual DLM output that gives the maximum likelihood from among the information of each likelihood output from the likelihood calculation unit 633. The ideal output unit 632a estimates the state of the optical transmission path corresponding to the identified virtual DLM output as the output of the characteristics of the ideal devices of the optical transmission system 100a (step S203). The ideal output unit 632a outputs the information of the estimated output of the characteristics of the ideal devices to the outside.

[0056] In the optical transmission system 100a configured as described above, first, the likelihoods of each of the device characteristics estimated by the simulation unit 61 and the characteristics of the devices provided in the optical transmission path obtained in the real space are calculated. Then, in the optical transmission system 100a, a virtual DLM output that gives the maximum likelihood among the calculated multiple likelihoods is identified. Then, in the optical transmission system 100a, the state (ideal output) of the optical transmission path corresponding to the identified virtual DLM output is estimated as the output of the characteristics of the ideal devices of the optical transmission system 100a. In this way, it is possible to estimate the state of the optical transmission path close to the DLM output obtained in the real space. Therefore, it becomes possible to accurately estimate the characteristics of the devices constituting the transmission system.

[0057] (Modification common to the first and second embodiments) In the above-described configuration, the configuration in which the DLM output is calculated by the optical receiver 2 is shown, but the DLM output may be calculated by the network controllers 6, 6a. When configured in this way, the functions of the digital signal processing unit 22 of the optical receiver 2 are implemented in the network controllers 6, 6a.

[0058] In each embodiment, the configuration for obtaining the DLM output does not have to be limited to the configuration of the digital signal processing unit 22 described above. The digital signal processing unit 22 may have other configurations as long as it can obtain the DLM output. FIG. 9 is a diagram showing another example of the functional configuration of the digital signal processing unit 22a. The digital signal processing unit 22a includes a chromatic dispersion compensation unit 29, an adaptive equalization unit 24, a frequency offset compensation unit 25, a carrier phase noise compensation unit 26, a chromatic dispersion addition unit 30, a non-linear optical compensation unit 23, a coefficient update unit 27, and a transmission characteristic estimation unit 28. The digital signal processing unit 22a further includes a chromatic dispersion compensation unit 29 and a chromatic dispersion addition unit 30 in addition to the configuration of the digital signal processing unit 22.

[0059] The functions of the adaptive equalization unit 24, the frequency offset compensation unit 25, the carrier phase noise compensation unit 26, the non-linear optical compensation unit 23, the coefficient update unit 27, and the transmission characteristic estimation unit 28 are the same as those in FIG. 3, so the description thereof is omitted. The chromatic dispersion compensation unit 29 compensates for the distortion caused by chromatic dispersion occurring in the optical transmission line 3. Specifically, the chromatic dispersion compensation unit 29 multiplies the received signal in the frequency domain by a predetermined value (for example, exp^(-jβ k ω 2 )) to perform chromatic dispersion compensation. The chromatic dispersion addition unit 30 is a functional unit that adds the chromatic dispersion compensated by the chromatic dispersion compensation unit 29 to the signal again. Specifically, the chromatic dispersion addition unit 30 multiplies the received signal in the frequency domain by the reciprocal of the value multiplied by the chromatic dispersion compensation unit 29 (for example, exp^(+jβ k ω 2 )) to perform chromatic dispersion addition.

[0060] Some or all of the functions of the above-described optical transmitter 1, optical receiver 2, and network controllers 6 and 6a may be realized by a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed to realize it. Here, the "computer system" shall include hardware such as an OS and peripheral devices. Further, the "computer-readable recording medium" refers to a portable medium such as a flexible disk, magneto-optical disk, ROM, CD-ROM, etc., and a storage device such as a hard disk incorporated in a computer system.

[0061] Furthermore, the "computer-readable recording medium" also includes those that dynamically hold a program for a short time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, and those that hold a program for a certain period of time, such as a volatile memory inside a computer system that serves as a server or client in that case. Also, the above program may be for realizing a part of the aforementioned functions, and may further be realized in combination with a program already recorded in a computer system for realizing the aforementioned functions, or may be realized using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0062] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and designs and the like within the scope not departing from the gist of the present invention are also included.

Industrial Applicability

[0063] The present invention can be applied to a technique for estimating the characteristics of devices constituting an optical transmission system.

Explanation of Reference Numerals

[0064] 100, 100a... optical transmission system, 1... optical transmitter, 2... optical receiver, 21... coherent receiver, 22... digital signal processing unit, 23... non-linear optical compensation unit, 231... linear compensation unit, 232... non-linear compensation unit, 233... Fourier transform unit, 234... chromatic dispersion compensation unit, 235... inverse Fourier transform unit, 24... adaptive equalization unit, 25... frequency offset compensation unit, 26... carrier phase noise compensation unit, 27... coefficient update unit, 28... transmission characteristic estimation unit, 29... chromatic dispersion compensation unit 29, 30... chromatic dispersion addition unit, 3... optical transmission line, 31A... relay node, 6, 6a... network controller, 61... simulation unit, 62, 62a... memory unit, 63, 63a... ideal output estimation unit, 631... filter construction unit, 632, 632a... ideal output unit, 633... likelihood calculation unit

Claims

1. A network controller provided in an optical transmission system in which an optical transmitter and an optical receiver communicate via an optical transmission line, a simulation unit that constructs a plurality of simulation models by virtually reproducing the state of the optical transmission line in an optical transmission system including the optical transmitter, the optical receiver, and the optical transmission line in different virtual spaces, and estimates the characteristics of the devices provided on the optical transmission line for each simulation model; an ideal output estimation unit that estimates and outputs the characteristics of an ideal device based on the characteristics of the device estimated by the simulation unit and the characteristics of the device provided on the optical transmission line obtained in the real space; comprising: the state of the optical transmission line in the optical transmission system is different for each simulation model, further comprising a storage unit that stores one or more first data sets associating the characteristics of the device estimated by the simulation unit with an ideal output representing the characteristics of an ideal device, and one or more second data sets associating the characteristics of the device previously acquired in the real space with an ideal output representing the characteristics of an ideal device; the ideal output estimation unit mixes the first data set and the second data set at an arbitrary ratio, performs an operation based on the ideal output and the characteristics of the device, constructs a digital filter that minimizes the mean squared error, and inputs the characteristics of the device provided on the optical transmission line obtained in the real space during communication to the constructed digital filter, thereby estimating the characteristics of the ideal device. A network controller.

2. A network controller provided in an optical transmission system in which an optical transmitter and an optical receiver communicate via an optical transmission line, a simulation unit that constructs a plurality of simulation models by virtually reproducing the state of the optical transmission line in an optical transmission system including the optical transmitter, the optical receiver, and the optical transmission line in different virtual spaces, and estimates the characteristics of the devices provided on the optical transmission line for each simulation model; an ideal output estimation unit that estimates and outputs the characteristics of an ideal device based on the characteristics of the device estimated by the simulation unit and the characteristics of the device provided on the optical transmission line obtained in the real space; comprising: the state of the optical transmission line in the optical transmission system is different for each simulation model, The ideal output estimation unit calculates the likelihood between each of the characteristics of the device estimated by the simulation unit and the characteristics of the device provided in the optical transmission path obtained in the real space, and estimates, as the characteristics of the ideal device, the characteristics of the device estimated by the simulation unit with the highest calculated likelihood. A network controller.

3. Further comprising a digital signal processing unit that estimates the characteristics of a device provided in the optical transmission path based on the output of the optical receiver that has received the optical signal transmitted from the optical transmitter. The network controller according to claim 1 or 2.

4. An estimation method performed by a network controller provided in an optical transmission system in which an optical transmitter and an optical receiver communicate via an optical transmission path, Constructing a plurality of simulation models by virtually reproducing the state of the optical transmission path in the optical transmission system including the optical transmitter, the optical receiver, and the optical transmission path in different virtual spaces, and estimating the characteristics of the device provided in the optical transmission path for each simulation model. Based on the estimated characteristics of the device and the characteristics of the device provided in the optical transmission path obtained in the real space, estimate and output the characteristics of the ideal device. The state of the optical transmission path in the optical transmission system is different for each simulation model. One or more first data sets associating the estimated characteristics of the device with an ideal output representing the characteristics of the ideal device, and one or more second data sets associating the characteristics of the device previously obtained in the real space with an ideal output representing the characteristics of the ideal device are mixed at an arbitrary ratio, and a digital filter that minimizes the mean squared error is constructed by performing an operation based on the ideal output and the characteristics of the device. By inputting the characteristics of the device provided in the optical transmission path obtained in the real space during communication to the constructed digital filter, the characteristics of the ideal device are estimated. An estimation method.

5. An estimation method performed by a network controller provided in an optical transmission system in which an optical transmitter and an optical receiver communicate via an optical transmission path, By virtually reproducing the state of the optical transmission line in an optical transmission system including the optical transmitter, the optical receiver, and the optical transmission line in different virtual spaces, a plurality of simulation models are constructed, and the characteristics of the devices provided on the optical transmission line are estimated for each simulation model. Based on the estimated characteristics of the devices and the characteristics of the devices provided on the optical transmission line obtained in the real space, the characteristics of the ideal devices are estimated and output. The state of the optical transmission line in the optical transmission system is different for each simulation model. A method of estimation for calculating the likelihood of each of the estimated device characteristics and the characteristics of the devices provided on the optical transmission line obtained in the real space, and estimating the characteristics of the estimated device with the highest calculated likelihood as the characteristics of the ideal device.

6. A computer program for causing a computer to function as the network controller according to any one of Claims 1 to 3.

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