Analysis of cross phase modulation with first-and second order GVD in WDM of fiber optic communication system

Abstract

With increased channel capacity, launched optical powers, bit rates and number of wavelength channels, the cross phase modulation (XPM) has become the most important nonlinear effect and limits system performance. On the other hand, group velocity dispersion (GVD) is one of the linear effects in the optical fiber that also restricts bit rates. In high bit rate and first order GVD compensated system, the effect of second order GVD become significant and also play a critical role in limiting the system performance. As a result the combined effects of XPM with first- and second order GVD cause further deterioration of transmission performance in a WDM system. In this research work, analysis has been carried out to find expressions of pulse broadening factor as well as normalized output by solving the nonlinear Schrodinger equation (NLSE) analytically, considering the effect of XPM with first- and second order GVD. The results are evaluated at various data rates, different input powers as a function of transmission distance using standard single mode fiber (SSMF) and large effective area fiber (LEAF). The pulse broadening is strongly dependent on the effects of XPM with first- and second order GVD. Though at shorter distance and low bit rates the effect of second order GVD is not noticeable but as the bit rate increases its effect becomes significant and impacts the system performance. It is observed that the data rate and fiber length have higher impact on pulse broadening than the input power. The results are computed for SSMF and LEAF using analytical derivation and numerical simulation done through split step Fourier method with same data rate and input power. It is found that the effects of XPM with first- and second orders GVD is more effective in SSMF fiber than that of LEAF fiber. Thus the findings of this work can predict the amount of performance degradation due to the effects of XPM with first- and second order GVD and may be helpful to design high speed long haul WDM fiber-optic transmission link.