Cross Phase Modulation Effect In Dense Wavelength Division Multiplexing

Dense Wavelength Division Multiplexing (DWDM) is a new domain in optics communication, and is attracting more and more attention. Tough DWDM can improve the bandwidth of high speed net efficiently, it also causes some disadvantages. This paper will discuss the effect of Cross-phase modulation (XPM). For a less channel system, people have gained many results in theory and practice; but for the condition which capacity is bigger than 10Gb and channel spacing smaller than 0.8 nm.This paper will use split-step Fourier to solve the complex nonlinear Schrodinger equation (NLSE). In the frequency domain, the analysis resovle of NLSEcan explain the initial stage of the modulation instability. On the other hand, the whole character of the modulated unstable continuous waves can be discussed by this method. The results are suitable to normal or abnormal dispersion regimes. The modulation instability decrease the signal's power, amplifier the noise and decrease the SNR of DWDM system. Besides, the effect of modulation instability is different from different channel. The effect on short waves is stronger than that of the long wave; it will make the devition will accumulate with fiber length. In this paper, the selection of parameters is suitable,we also analyse the reason why we choose it. For a system or a wavelength, the transmitter length, signal power and the channel separation must be matched to make the SNR reach its maximum.In dense wavelength division multiplexing optical transmission systems, cross phase modulation due to Ken effect causes phase shift and intensity modulation in each channel, which will lead the channel capacity to be a random variable. In this letter, we present an expression of the channel capacity which considers XPM effect and demonstrate the correctness and accuracy of this method by numeric simulation.