Nonlinear equalization method for high-order QAM coherent light system

Abstract

According to the nonlinear equalization method for the high-order QAM coherent light system, after receiving end data is subjected to phase noise compensation, an FCM algorithm is firstly used for achieving effective clipping of training data, meanwhile, test data is subjected to classification judgment, and therefore a test set and a training set of a follow-up KNN algorithm are greatly reduced.The method is based on a coherent light 16QAM system with the transmission rate of 112 Gb/s and the transmission distance of 160 km, and non-linear equalization simulation verification is carried out.Simulation results show that the same system nonlinear damage compensation effect as a traditional KNN algorithm can be obtained, but the algorithm complexity of the method is far lower than that ofthe traditional KNN algorithm, and the algorithm running time is far shorter than that of the KNN algorithm. According to the invention, the application of the coherent light QAM system in medium andlong distance optical fiber transmission can be greatly promoted.

Description

Technical field [0001] The present invention belongs to the technical field of optical communication networks, and particularly relates to a method for nonlinear equalization of coherent optical quadrature amplitude modulation (QAM) communication systems. Background technique [0002] High-order modulation formats such as multi-phase shift keying and high-order QAM modulation have high spectral efficiency and have been widely used to increase the transmission capacity of optical fiber networks. These high-order modulation signals are more susceptible to various noises in optical fiber transmission systems, and generally require a higher optical signal-to-noise ratio in order to obtain ideal bit error rate performance. Furthermore, in order to improve the optical signal-to-noise ratio, a high-energy signal at the transmitting end is required, but after the high-energy signal at the transmitting end enters the optical fiber, it is inevitably affected by the nonlinearity of the opti...

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Problems solved by technology

[0006] In order to overcome the shortcomings of the traditional KNN method in the coherent optical 16QAM system with high computational complexity, the present invention proposes a method combining FCM and KNN for the nonlinear equalization of the coherent optical 16QAM system. This method is effective by using the FCM method Reduce the size of the training set of the KNN method, and at the same time use the combination of traditional judgment and KNN method to effectively reduce the size of the test set of the KNN method, thus greatly reducing the computational complexity of the KNN method while maintaining the good nonlinear equalization effect of the KNN method Spend

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