Nonlinear effect suppression method and system for CO-OFDM (Coherent Optical Orthogonal Frequency Division Multiplexing) system

Abstract

The invention discloses a nonlinear effect suspension method and system for a CO-OFDM (Coherent Optical Orthogonal Frequency Division Multiplexing) system. The nonlinear effect suspension method comprises the steps of: at a system sending end, for a random group, acquiring a conjugate symbol in phase conjugation with a pilot symbol so as to obtain a corresponding neighbor estimation group; carrying out carrier mapping on the pilot symbol, the conjugate symbol and a data symbol and sending a carrier to a system receiving end; at the system receiving end, carrying out frequency domain signal reduction on the carrier sent from the system sending end, and extracting the pilot symbol, the conjugate symbol and the data symbol; carrying out coherent superposition on the extracted pilot symbol andthe corresponding conjugate symbol so as to compensate a nonlinear phase shift in the pilot symbol; and estimating a nonlinear phase shift of the data symbol in the same neighbor estimation group byutilizing the extracted pilot symbol and the corresponding conjugate symbol, and carrying out compensation on the nonlinear phase shift of the data symbol. According to the invention, damage caused bya nonlinear effect in the CO-OFDM system can be effectively and comprehensively compensated in real time.

Description

technical field [0001] The invention belongs to the field of optical communication, and more specifically relates to a method and system for suppressing nonlinear effects of a CO-OFDM system. Background technique [0002] In the optical communication CO-OFDM (Coherent Optical Orthogonal Frequency Division Multiplexing, coherent optical orthogonal frequency division multiplexing) system, the subcarrier frequency intervals are strictly equal, which is easy to meet the phase matching conditions of the nonlinear four-wave mixing effect, which leads to serious carrier interfering. At the same time, because the CO-OFDM signal has a high peak-to-average power ratio, it is easier to reach the threshold of Kerr nonlinearity and is further affected by self-phase modulation and cross-phase modulation. How to effectively suppress the nonlinear effect in the fiber link is a key issue in CO-OFDM technology. [0003] The existing carrier-pilot-based channel monitoring schemes can only ap...

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Problems solved by technology

[0003] The existing carrier-pilot-based channel monitoring schemes can only approximate random phase noise, and cannot eliminate the phase offset related to the position of the carrier spectrum caused by nonlinear effects, and will reduce the spectrum efficiency; the traditional back-to-back Due to its extremely high computational complexity, the transmission algorithm is difficult to have a good compensation effect in the real-time compensation of the nonlinear damage of the CO-OFDM system

Therefore, there is currently no effective and comprehensive compensation method for the fiber nonlinear damage of the CO-OFDM system.

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