A Study on Modulation Formats to improve performance of Optical Systems

In this paper a study on modulation formats like non return to zero (NRZ), return to zero (RZ) and carrier suppressed return to zero (CSRZ) in terms of generation, dispersion analysis and performance at the receiver end has been done for a standard single mode fiber (SMF) of fixed length and data rate. The principle of external modulation through a Mach Zehnder Modulator (MZM) is been employed for the generation of the various formats. Linear effect or dispersion performance of formats alone is considered here. A dispersion compensation technique based on dispersion compensation fibers (DCF) that improves the performance of the optical link is also studied. The performances have been analyzed in terms of bit error rate (BER) and quality factor (Q-factor). The study reveals that RZ exhibits superior performance over the other formats in terms of dispersion tolerance, BER and Q-factor values. It is also shown that by introducing a DCF module system performance can be improved.