Impact of intra-channel cross-phase modulation on high speed optical fiber communication system

Abstract

In this thesis, analytical estimation of phase fluctuations due to intra-channel crossphase modulation (IXPM) on return-to-zero (RZ) pulse has been studied in details for both uncompensated single line transmission and periodically dispersion managed (DM) system. We have investigated optical pulse propagation operating at a speed of 40 Gb/s for both systems. The basic theories for the analyses employed in this thesis for optical pulse transmission is presented after making a brief discussion on fiber nonlinearities. First fundamental equations of optical pulse propagation in a fiber have been studied assuming a suitable solution for the Nonlinear Schrödinger (NLS) equation. Here we use variational method to examine the IXPM induced phase fluctuation analytically. Various dynamical equations have been derived with IXPM as a source of perturbation. We have obtained several ordinary differential equations for various pulse parameters. These pulse parameters are amplitude (A), reciprocal of pulse width (p), linear chirp (C), central frequency (κ), central time position (T) and the phase of the pulse (θ). These ordinary differential equations have been solved by Runge-Kutta method to find out the phase fluctuations due to intra-channel cross-phase modulation. The effects of IXPM induced phase fluctuation with the variation of different parameters have been explored for both uncompensated single line transmission and DM system. The amount of phase shift is investigated by changing different parameters such as transmission distance, input power, duty cycle, bit-rate and dispersion map strength. Different transmission models will be explored to check an optimum model. Finally, split-step Fourier method (SSFM) is used in some cases to achieve the full numerical simulation and to validate the accuracy of proposed analytical models.