Non-decision-aided sub-symbol optical phase noise suppression method

Abstract

The invention discloses a non-decision-aided low-complexity time domain sub-symbol optical phase noise suppression method in a coherent light orthogonal frequency division multiplexing system. The method comprises following steps: firstly, cutting received time domain signals into blocks, thus obtaining zero filled sub-symbol vectors; secondly, in adoption of the features of specially designed periodical comb type pilot frequencies, obtaining an observing matrix in a mode without multiplication, extracting offline stored vectors based on pilot frequencies; then estimating sub-symbol optical phase noises by a least square method according to the obtained observing matrix and vectors based on pilot frequencies, compensating the optical phase noises; and finally, switching the signals after phase noise compensation to a frequency domain for channel equalization, and judging and outputting the equalized signals. According to the method of the invention, the complexity is low; the practicability is strong; the demand of the system for the line width of a laser light source is effectively reduced; and the tolerance of the system to the optical phase noises is improved.

Description

technical field [0001] The invention belongs to the technical field of optical communication, and in particular relates to a non-judgment-assisted subsymbol optical phase noise suppression method in a coherent optical orthogonal frequency division multiplexing system. Background technique [0002] Compared with single-carrier coherent optical communication technology, coherent optical orthogonal frequency division multiplexing (CO-OFDM) system can achieve high spectral efficiency, flexible spectrum allocation, and efficient channel equalization. One of the layer technologies. But a major defect of CO-OFDM system is that it is extremely sensitive to optical phase noise. The impact of optical phase noise on CO-OFDM systems includes two parts: common phase noise (CPE) and inter-subcarrier interference (ICI). Most current low-complexity phase noise estimation schemes only consider the influence of the CPE part, and treat the ICI part as Gaussian white noise. When the phase no...

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Problems solved by technology

Although this scheme can suppress the influence of CPE and ICI at the same time, there is a small-angle approximation in the system modeling process, that is, sinθ≈θ. When the phase noise is relatively large, the approximation is no longer valid, and the performance of the algorithm is limited. In addition, , another disadvantage of this method is that in order to estimate the difference between each sub-symbol, the algorithm needs to use multiple multiplication operations, and the complexity is relatively high

[0004] In general, the existing CO-OFDM system phase noise suppression methods have the following deficiencies: (1) For the scheme that only considers the CPE, it can only estimate the average phase noise (CPE) of the entire OFDM symbol, but cannot track Changes of noise within symbols; (2) For the currently proposed ICI suppression scheme, although the influence of phase noise can be effectively suppressed, in order to obtain the corresponding observation matrix, the algorithm needs to use multiple Fourier (inverse) transforms operation, the algorithm complexity is high

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