JP-7856930-B2 - Estimation device, filter generation device, estimation method, and filter generation method

JP7856930B2JP 7856930 B2JP7856930 B2JP 7856930B2JP-7856930-B2

Inventors

五十嵐稜
可児淳一
原一貴
胡間遼

Assignees

ＮＴＴ株式会社

Dates

Publication Date: 20260512
Application Date: 20230111

Claims (7)

An electric field estimation unit estimates a simulated signal of the output electric field waveform using a filter of tap coefficients generated for each combination of optical intensity and transmission distance of the first input electric field waveform based on the first input electric field waveform at the input end of the transmission line and the output electric field waveform at the output end of the transmission line, and the generated second input electric field waveform. The system includes an error rate estimation unit that estimates the error rate of the code sequence at the output terminal of the transmission line based on a simulated signal of the output electric field waveform , The filter is an estimation device that outputs a simulated signal of the output electric field waveform, which is affected by the linear and nonlinear waveform characteristics when the second input electric field waveform is transmitted along the transmission path of the transmission distance, using the tap coefficient selected based on the light intensity of the second input electric field waveform and the transmission distance.
The estimation device according to claim 1, wherein the filter applies at least the nonlinear waveform distortion among the linear waveform distortion and nonlinear waveform distortion occurring in the transmission line using the tap coefficient.
The estimation device according to claim 1, wherein the simulated signal of the output electric field waveform is an electric field waveform or an intensity waveform.
The system includes a filter unit that generates a tap coefficient for each combination of light intensity and transmission distance based on a dataset which is a combination of the light intensity and transmission distance of the input electric field waveform at the input end of the transmission line and the output electric field waveform at the output end of the transmission line . The filter unit receives the input electric field waveform, or a waveform obtained by performing linear change processing in the transmission line on the input electric field waveform. The filter unit generates the tap coefficients such that the difference between the shape of the output electric field waveform and the shape of the waveform output from the filter unit is reduced. Filter generating device.
The filter generation apparatus according to claim 4, wherein the filter unit registers the tap coefficients in a lookup table.
An estimation method performed by an estimation device, A step of estimating a simulated signal of the output electric field waveform using a filter of tap coefficients generated for each combination of optical intensity and transmission distance of the first input electric field waveform based on the first input electric field waveform at the input end of the transmission line and the output electric field waveform at the output end of the transmission line, and the generated second input electric field waveform. The steps include: estimating the error rate of the code sequence at the output terminal of the transmission line based on a simulated signal of the output electric field waveform; The filter is an estimation method that outputs a simulated signal of the output electric field waveform that is affected by the linear and nonlinear waveform characteristics when the second input electric field waveform is transmitted along the transmission path of the transmission distance, using the tap coefficient selected based on the light intensity of the second input electric field waveform and the transmission distance.
A filter generation method performed by a filter generation device, The step includes generating a tap coefficient for each combination of light intensity and transmission distance based on a dataset which is a combination of the light intensity and transmission distance of the input electric field waveform at the input end of the transmission line and the output electric field waveform at the output end of the transmission line . In the generation step described above, the input electric field waveform, or a waveform obtained by performing linear change processing in the transmission line on the input electric field waveform, is input to the filter unit. The filter unit generates the tap coefficients such that the difference between the shape of the output electric field waveform and the shape of the waveform output from the filter unit is reduced. Filter generation method.

Description

The present invention relates to an estimation device, a filter generation device, an estimation method, and a filter generation method. In an optical communication system using ROADM (reconfigurable optical add/drop multiplexer) (see Non-Patent Document 1), each node in the transmission path forwards the optical signal transmitted from the first communication device to the second communication device using an optical path. Furthermore, in an All Photonics Network (APN), the optical paths are connected end-to-end without any photoelectric conversion being performed on the optical signals. Figure 11 shows an example of the configuration of an optical communication system. The optical communication system illustrated in Figure 11 comprises a first communication device, a second communication device, and a transmission line. The transmission line illustrated in Figure 11 comprises a first node, a second node, a third node, a fourth node, and a fifth node. Each node also includes an optical switch (not shown). Each node transmits the optical signal without performing photoelectric conversion. As a result, the optical signal transmitted from the first communication device is transmitted to the second communication device while remaining in its original optical (electric field waveform) form. In an all-photonics network, when a signal requesting connection to a second communication device is transmitted from the first communication device, an appropriate optical path from the first communication device to the second communication device is selected from among multiple optical paths in the transmission line. Here, since the modulation method of the optical signal, the transmission rate, the transmission distance (length of the transmission path), the type of optical fiber used in the transmission path, and the gain of the optical amplifier through which the optical signal is transmitted differ for each optical path, the code error rate in the second communication device also differs for each optical path. For this reason, it is necessary to select an optical path capable of error-free transmission (an optical path in which the code error rate is less than a predetermined value) from among multiple optical paths. The optical paths may be selected based on the results of verifying whether each optical path is error-free by actually transmitting an optical signal through it. However, in this case, it takes time for multiple optical paths to be covered, so an enormous amount of time is required to activate the optical paths. Therefore, in order to activate the optical paths in a short time, it is effective to select the optical path that is capable of error-free transmission based on the pre-estimated code error rate for each optical path. One method for estimating the code error rate in an optical communication system is to use propagation simulation to estimate the code error rate using an estimation device. For example, the estimation device estimates the electric field waveform of an optical signal transmitted through a transmission path having an optical fiber using propagation simulation. The estimation device simulates the electric field waveform in a second communication device by adding appropriate noise to the electric field waveform. The estimation device identifies the code sequence received by the second communication device (received code sequence) by performing a threshold judgment process on the simulation result. The estimation device estimates the code error rate based on the difference between the identified received code sequence and the code sequence transmitted from the first communication device (transmitted code sequence). The estimation device accurately estimates the change in the electric field waveform of an optical signal transmitted through a transmission path by performing a predetermined algorithmic processing (e.g., the Split Step Fourier Method (SSFM)) on the nonlinear Schrödinger equation. In this case, the estimation device estimates the electric field waveform (simulated signal) that has undergone linear changes (wavelength dispersion) and nonlinear changes (self-phase modulation) due to transmission. This allows for accurate estimation of the change in the electric field waveform of an optical signal transmitted through a transmission path, even when nonlinear waveform distortion occurs in the electric field waveform. However, in methods based on the split-step Fourier method, the fiber section transmitting the optical signal is divided, and the calculation of the electric field waveform for each divided fiber section is repeated sequentially. Therefore, the calculation time increases as the transmission distance increases. Consequently, it is difficult to apply this estimation method to all-photonic networks that require real-time operation. To solve these problems, "GNPy" is provided as a method for estimating the code error rate in a short time (see Non-Patent Document 2). In "