US-12621059-B2 - Decoding method using polarization time block coding and decoding device for performing the method

US12621059B2US 12621059 B2US12621059 B2US 12621059B2US-12621059-B2

Abstract

Provided is a decoding method using polarization time block coding (PTBC) and a decoding device for performing the decoding method. The decoding method includes branching received symbols consecutively received according to a symbol period into two paths, delaying a first received symbol corresponding to a first path between the two paths by the symbol period in which the received symbols are received, performing a complex conjugate operation on a second received symbol corresponding to a second path between the two paths, compensating for channel distortion of the first received symbol delayed by the symbol period and the second received symbol on which the complex conjugate operation is performed, through an equalizer in the decoding device, and restoring a transmission symbol by performing phase restoration on the first received symbol and the second received symbol for which the channel distortion is compensated for, through a phase compensator in the decoding device.

Inventors

Jung-Yeol OH

Assignees

ELECTRONICS AND TELECOMMUNICATIONS RESEARCH INSTITUTE

Dates

Publication Date: 20260505
Application Date: 20240119
Priority Date: 20230828

Claims (13)

1 . A decoding method, performed by a decoding device, using polarization time block coding (PTBC), the decoding method comprising: branching received symbols consecutively received according to a symbol period into two paths; delaying a first received symbol corresponding to a first path between the two paths by the symbol period in which the received symbols are received; performing a complex conjugate operation on a second received symbol corresponding to a second path between the two paths; compensating for channel distortion of the first received symbol delayed by the symbol period and the second received symbol on which the complex conjugate operation is performed, through an equalizer in the decoding device; and restoring a transmission symbol by performing phase restoration on the first received symbol and the second received symbol for which the channel distortion is compensated for, through a phase compensator in the decoding device.
2 . The decoding method of claim 1 , wherein the first received symbol and the second received symbol comprise identical symbols by copying the received received symbols.
3 . The decoding method of claim 1 , wherein the compensating for the channel distortion comprises compensating for the channel distortion of the first received symbol and the second received symbol using the equalizer based on a channel filter coefficient set by a channel coefficient for X polarization and a channel coefficient for Y polarization.
4 . The decoding method of claim 1 , further comprising: performing down-sampling on the first received symbol and the second received symbol for which the channel distortion is compensated for, wherein the restoring of the transmission symbol comprises restoring the transmission symbol by performing the phase restoration on the first received symbol and second received symbol on which the down-sampling is performed.
5 . A non-transitory computer-readable storage medium storing instructions that, when executed by a processor, cause the processor to perform the method of claim 1 .
6 . A decoding device comprising: one or more processors; and a memory configured to load or store a program executed by the one or more processors, wherein the program comprises instructions configured to branch received symbols consecutively received according to a symbol period into two paths, delay a first received symbol corresponding to a first path between the two paths by the symbol period in which the received symbols are received, perform a complex conjugate operation on a second received symbol corresponding to a second path between the two paths, compensate for channel distortion of the first received symbol delayed by the symbol period and the second received symbol on which the complex conjugate operation is performed, through an equalizer in the decoding device, and restore a transmission symbol by performing phase restoration on the first received symbol and the second received symbol for which the channel distortion is compensated for, through a phase compensator in the decoding device.
7 . The decoding device of claim 6 , wherein the first received symbol and the second received symbol comprise identical symbols by copying the received received symbols.
8 . The decoding device of claim 6 , wherein the one or more processors are configured to compensate for the channel distortion of the first received symbol and the second received symbol using the equalizer based on a channel filter coefficient set by a channel coefficient for X polarization and a channel coefficient for Y polarization.
9 . The decoding device of claim 6 , wherein the one or more processors are configured to perform down-sampling on the first received symbol and the second received symbol for which the channel distortion is compensated for and restore the transmission symbol by performing the phase restoration on the first received symbol and the second received symbol on which the down-sampling is performed.
10 . An optical receiver comprising a decoding device, the optical receiver comprising: a local oscillator (LO); an optical mixer configured to mix a polarization component of a local oscillation signal output from the LO and a polarization component of an optical signal transmitted and received to and from an optical transmitter; an optical detector configured to convert optical signals output from the optical mixer into electrical analog signals and transmit the electrical analog signals to an optical amplifier; an analog-to-digital converter (ADC) configured to convert an electrical analog signal output from the optical amplifier into a digital signal; and a decoding device configured to restore an original signal transmitted from the optical transmitter from digital signals output from the ADC, wherein the decoding device is configured to branch received symbols consecutively received according to a symbol period into two paths, delay a first received symbol corresponding to a first path between the two paths by the symbol period in which the received symbols are received, perform a complex conjugate operation on a second received symbol corresponding to a second path between the two paths, compensate for channel distortion of the first received symbol delayed by the symbol period and the second received symbol on which the complex conjugate operation is performed, through an equalizer in the decoding device, and restore a transmission symbol by performing phase restoration on the first received symbol and the second received symbol for which the channel distortion is compensated for, through a phase compensator in the decoding device.
11 . The optical receiver of claim 10 , wherein the first received symbol and the second received symbol comprise identical symbols by copying the received received symbols.
12 . The optical receiver of claim 10 , wherein the decoding device is configured to compensate for the channel distortion of the first received symbol and the second received symbol using the equalizer based on a channel filter coefficient set by a channel coefficient for X polarization and a channel coefficient for Y polarization.
13 . The optical receiver of claim 10 , wherein the decoding device is configured to perform down-sampling on the first received symbol and the second received symbol for which the channel distortion is compensated for and restore the transmission symbol by performing the phase restoration on the first received symbol and the second received symbol on which the down-sampling is performed.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of Korean Patent Application No. 10-2023-0112964, filed on Aug. 28, 2023, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes. BACKGROUND 1. Field of the Invention One or more embodiments relate to a decoding method using polarization time block coding (PTBC) technology in a coherent optical communication system and a device for performing the same. 2. Description of the Related Art A coherent optical communication system provides higher transmission capacity and spectral efficiency compared to an intensity modulation/direct detection (IM/DD) optical communication system. However, such a coherent optical communication system requires an optical receiver with a dual polarization structure having a polarization diversity function because the state of polarization of an optical signal transmitted from an optical fiber changes randomly. Since the optical receiver with a dual polarization structure has high optical component complexity, a coherent optical communication method using polarization time block coding (PTBC) using an Alamouti code is proposed as a method of implementing a cost-effective coherent optical receiver. The coherent optical communication method using PTBC provides a method of Alamouti-encoding so that two adjacent symbols in the time domain are orthogonal to each other for X polarization and Y polarization when generating a transmission signal from a coherent optical transmitter and restoring an original signal using a decoding device to which PTBC technology is applied in a coherent optical receiver. Such a coherent optical communication method using PTBC may realize a coherent optical receiver with a single polarization reception structure rather than an existing dual polarization reception structure, there is an advantage of reducing optical components by 50% compared to an existing method. However, the decoding device using PTBC in a coherent optical receiver with a single polarization reception structure according to the related art has a problem in that the performance degradation of an equalizer may occur due to the bandwidth limitation of optical components. More specifically, in the coherent optical receiver with a single polarization reception structure according to the related art, a received symbol may be divided into an odd-numbered term and an even-numbered term through a serial-parallel converter, so signal components of a symbol scattered in an adjacent symbol are separated into different equalizers and there may be a problem that an equalizer does not sufficiently compensate for the signal. SUMMARY Embodiments provide a structure of a decoding device that may improve the performance degradation of an equalizer caused by a bandwidth limitation effect of optical components in a coherent optical receiver. However, the technical aspects are not limited to the aforementioned aspects, and other technical aspects may be present. According to an aspect, there is provided a decoding method, performed by a decoding device, using polarization time block coding (PTBC), the decoding method including branching received symbols consecutively received according to a symbol period into two paths, delaying a first received symbol corresponding to a first path between the two paths by the symbol period in which the received symbols are received, performing a complex conjugate operation on a second received symbol corresponding to a second path between the two paths, compensating for channel distortion of the first received symbol delayed by the symbol period and the second received symbol on which the complex conjugate operation is performed, through an equalizer in the decoding device, and restoring a transmission symbol by performing phase restoration on the first received symbol and the second received symbol for which the channel distortion is compensated for, through a phase compensator in the decoding device. The first received symbol and the second received symbol may include identical symbols by copying the received received symbols. The compensating for the channel distortion may include compensating for the channel distortion of the first received symbol and the second received symbol using the equalizer based on a channel filter coefficient set by a channel coefficient for X polarization and a channel coefficient for Y polarization. The decoding method may further include performing down-sampling on the first received symbol and the second received symbol for which the channel distortion is compensated for. The restoring of the transmission symbol may include restoring the transmission symbol by performing the phase restoration on the first received symbol and second received symbol on which the down-sampling is performed. According to another aspect, there is provided a decoding device including one or more processors and a memory c