Construction method of mode-division multiplexing fiber-optic communication system and a constructed fiber-optic communication system

Patent metadata

Field	Value
Publication number	US-10868631-B2
Application number	US-201715768015-A
Country	US
Kind code	B2
Filing date	May 18, 2017
Priority date	Apr 28, 2017
Publication date	Dec 15, 2020
Grant date	Dec 15, 2020

Abstract

The present invention relates to a construction method of a mode-division multiplexing fiber-optic communication system, which includes following contents: converting multiple-input optical signals into optical propagation modes supported by a graded-index ring-core optical fiber at a transmitting end, after being multiplexed by a mode multiplexer, injecting the optical signals into the graded-index ring-core optical fiber for transmission; using a mode de-multiplexer to separate optical signals of different mode groups at a receiving end firstly; and for the separation of internal modes of the same mode group, adopting a multi-channel reception and a digital signal processing method based on a multiple-input multiple-output equalization for processing: for the separation of modes in a base mode group and a high-order mode group, using a digital signal processing algorithm including a 2×2 multiple-input multiple-output equalization and a digital signal processing algorithm including a 4×4 multiple-input multiple-output equalization for recovery processing, respectively. The method according to the present invention only needs to add an optical receiver and a digital signal processing module based on the 4×4 multiple-input multiple-output equalization repeatedly while adding the mode group to expand communication capacity. Compared with the prior art, the present invention has the characteristics of low complexity, high scalability and easy upgrading.

First claim

What is claimed is:

1. A construction method of a mode-division multiplexing fiber-optic communication system, the construction method comprises following contents:
converting multiple-input optical signals into orbital angular momentum (OAM) modes at a transmitting end, after being multiplexed by an OAM mode multiplexer, injecting the optical signals into a graded-index ring-core optical fiber for transmission;
using an OAM mode de-multiplexer to separate at least two different mode groups at a receiving end, then transmitting the optical signals in each mode group to corresponding OAM mode converters to be converted into Gaussian mode optical signals capable of supporting a single-mode optical fiber transmission which are then detected and received by coherent optical receivers to extract corresponding complex electrical signal, wherein the at least two different mode groups comprises at least two high-order OAM mode groups;
for a 2-way complex optical signal output after a base mode group or a zero-order mode group is received by the coherent optical receiver, using a digital signal processing algorithm including a 2×2 multiple-input multiple-output equalization for recovery processing; and
for a 4-way complex optical signal output after a high-order mode group or a non-zero-order mode group is received by the coherent optical receiver, using a digital signal processing algorithm including a 4×4 multiple-input multiple-output equalization for recovery processing,
wherein there are two modes consisting of zero-order OAM modes (OAM 0 modes) with two orthogonal polarizations in the base mode group or zero-order mode group, and
wherein there are only four modes consisting of OAM +n modes with the two orthogonal polarizations and OAM −n modes with the two orthogonal polarizations in each high-order mode group or non-zero-order mode group, where n is an integer more than zero and represents the mode-group order,
wherein the fiber-optic communication system further comprising:
the orbital angular momentum (OAM) mode multiplexer, the graded-index ring-core optical fiber, the OAM mode de-multiplexer, (2n+1) first OAM mode converters, (2n+1) coherent optical receivers, a 2×2 digital signal processing module and a 4×4 digital signal processing module; n is the number of high-order mode groups or non-zero-order mode groups, wherein an output end of the OAM mode multiplexer is connected with an input end of the graded-index ring-core optical fiber, an output end of the graded-index ring-core optical fiber is connected with an input end of the OAM mode de-multiplexer, an output end of the OAM mode de-multiplexer is connected with input ends of the (2n+1) first OAM mode converters respectively, output ends of the (2n+1) first OAM mode converters are connected with second input ends of the (2n+1) coherent optical receivers respectively, first input ends of the (2n+1) coherent optical receivers are connected with a local oscillator, output ends of the (2n+1) coherent optical receivers are connected with the 2×2 digital signal processing module or the 4×4 digital signal processing module,
wherein the optical communication system further includes (2n+1) polarization division multiplexing optical transmitters, wherein output ends of the (2n+1) polarization division multiplexing optical transmitters are connected to an input end of the OAM mode multiplexer.

2. The construction method of the mode-division multiplexing fiber-optic communication system according to claim 1 , wherein the digital signal processing algorithm including the 2×2 multiple-input multiple-output equalization comprises de-resampling and in-phase and quadrature (IQ) imbalance compensation, chromatic dispersion compensation, timing phase recovery, 2×2 multiple-input and multiple-output self-adaptive equalization, frequency offset estimation and compensation, carrier phase recovery, forward error correction, and signal demodulation and decision.

3. The construction method of the mode-division multiplexing fiber-optic communication system according to claim 1 , wherein the digital signal processing algorithm including the 4×4 multiple-input multiple-output equalization comprises de-resampling and in-phase and quadrature (IQ) imbalance compensation, chromatic dispersion compensation, timing phase recovery, 4×4 multiple-input and multiple-output self-adaptive equalization, frequency offset estimation and compensation, carrier phase recovery, forward error correction, and signal demodulation and decision.

4. The construction method of the mode-division multiplexing fiber-optic communication system according to claim 1 , wherein according to differences in a specific network environment and an optical fiber transmission distance, the digital signal processing algorithm including the 2×2 or 4×4 multiple-input multiple-output equalization is any one of a time-domain blind equalization algorithm, a frequency-domain blind equalization algorithm, a mixed time-domain and frequency-domain blind equalization algorithm, and a frequency domain equalization algorithm based on a training sequence; and according to a difference in a modulation format of a specific transmission signal, the digital signal processing algorithm including the 2×2 or 4×4 multiple-input multiple-output equalization is any one of a constant modulus algorithm, a cascade multi-mode algorithm, a radius guidance algorithm, or a least mean square algorithm.

5. The fiber-optic communication system according to claim 1 , wherein the number of the 2×2 digital signal processing modules is one, the number of the 4×4 digital signal processing modules is n; wherein an input end of the 2×2 digital signal processing module is connected with the output end of the coherent optical receiver corresponding to a base mode group or a zero-order mode group; and an input end of one 4×4 digital signal processing module is connected to the output end of the coherent optical receiver corresponding to one high-order mode group or non-zero-order mode group.

6. The fiber-optic communication system according to claim 1 , wherein the 2×2 digital signal processing module includes a resampling and in-phase and quadrature (IQ) imbalance compensation sub-module, a chromatic dispersion compensation sub-module, a timing phase recovery sub-module, a 2×2 multiple input multiple output self-adaptive equalization sub-module, a frequency offset estimation and compensation sub-module, a carrier phase recovery sub-module, and a forward error correction and demodulation and decision sub-module, which are connected in turn.

7. The fiber-optic communication system according to claim 1 , wherein the 4×4 digital signal processing module includes a resampling and in-phase and quadrature (IQ) imbalance compensation sub-module, a chromatic dispersion compensation sub-module, a timing phase recovery sub-module, a 4×4 multiple input multiple output self-adaptive equalization sub-module, a frequency offset estimation and compensation sub-module, a carrier phase recovery sub-module, and a forward error correction and demodulation and decision sub-module, which are connected in turn.

8. The construction method of the mode-division multiplexing fiber-optic communication system according to claim 1 , wherein the four modes included in each high-order mode group is highly degenerate to keep low differential mode delay in long-distance fiber transmission.

Assignees

• Univ Sun Yat Sen

Inventors

• Liu Jie
• Zhu Guoxuan
• Wu Xiong
• Chen Yujie
• Zhu Jiangbo
• Yu Siyuan

Classifications

• H04J14/04 Primary

  Mode multiplex systems · CPC title

• H04J14/07

  Orbital angular momentum [OAM] multiplex systems · CPC title

• H04J14/06

  Polarisation multiplex systems · CPC title

• H04L25/03057

  with a recursive structure (H04L25/03031 takes precedence) · CPC title

• H04L2025/03426

  transmission using multiple-input and multiple-output channels · CPC title