Fiber Nonlinearity Compensation Based On Inverse Scattering Method

With the rapid development of the multimedia services (i.e. cloud computing and big data), the demand of the transmission bandwidth has been growing year by year. Therefore, it puts forward more urgent demands for the existing metro and core networks. Optical fiber communication technology which has the advantages of large bandwidth, low loss, low cost and anti-electromagnetic interference, has been the main way of wire communication. However, the signal in transmission fiber would suffer various distortions such as chromatic dispersion, polarization mode dispersion and nonlinear effects and so on. With the development of coherent optical communication techniques, the linear and nonlinear distortions in optical fiber can be compensated by digital signal processing (DSP) algorithm. However, due to the randomness of nonlinear effect, there is not an effective method to completely compensate the nonlinear distortions.This paper mainly researches the inverse scattering method for the suppression of nonlinear effects. The main research content is as follows:Firstly, this paper introduces the principle of coherent optical communication systems. Among them, we focus on the related theoretical analysis of IQ modulation and coherent demodulation. At the same time, the theory of inverse scattering method is studied, and the process of the method would be derived in detail. We carry out numerical simulations in coherent optical communication transmission by using VPI simulation platform.Secondly, we study the nonlinear pre-compensation algorithm based on nonlinear spectrum management. The pre-compensation algorithm can equalize the linear and nonlinear spectrum of the signal so that the nonlinear Kerr effect can be mitigated. The transmission optical link with 3600km fiber length has a dispersion parameter of D=16.5 ps/nm/km, an attenuation of ?=0.2 dB/km and a nonlinear coefficient of ?=1.27 km-1·W-1. The simulation results show that the pre-compensation algorithm can achieve the performance improvement of up to 2.02 dB without ASE noise and 1.79 dB with ASE noise, respectively.Finally, we study another algorithm based on nonlinear Fourier transform. The pre-compensated signal needs to eliminate the nonlinear component of the signal nonlinear spectrum for suppressing the nonlinear effect and improving the quality of the signal. In this paper, we carry out numerical simulations with different modulation formats (i.e. QPSK, 160AM) The simulation results show that the proposed algorithm has the same advantage on mitigating nonlinear effect with the two modulation formats. Compared with the only dispersion compensation, the nonlinear compensation performance improvement of up to 2.33 dB for QPSK and 1.24 dB for 16QAM are achieved.