Performance analysis of CSRZ-DQPSK transmitter configurations for SBS tolerance in single mode fiber link

This paper investigates the SBS tolerance of two reduced complexity Carrier Suppressed Return to Zero- Differential Quadrature Phase Shift Keying (CSRZ-DQPSK) transmitter configurations and comparison with conventional 3 MZM scheme is reported. One scheme utilizes a single DD-MZM (Dual Drive Mach Zehnder Modulator) and a MZM (Mach Zehnder Modulator). Another configuration uses a single DD-MZM (Dual Drive Mach Zehnder Modulator). The link performance is evaluated for 10 Gbps data rate in a 50 Km single mode fiber link. From the simulation results, it is observed that two and one MZM based configurations provide 3 dB improvement in SBS threshold compared to the standard three MZM based implementation. Also, the performance of 2 MZM is slightly better than the single MZM configuration. As the input power is increased beyond SBS threshold, the roll off of Q- Factor is found to be 0.3/dBm for 3 MZM scheme where it is 0.05/dBm and 0.1/dBm for the 2 MZM and 1 MZM schemes. The BER performance is better at higher power levels, for the one and two MZM cases.