Comprehensive Assessment of New Modulation Techniques in 40Gb/s Optical Communication Systems

In this paper, comprehensive assessments are proposed for intensity modulations and phase modulations respectively. Several key performance features, like receiver sensitivity, chromatic dispersion tolerance, nonlinearity tolerance, and noise sensitivity were compared among these modulation techniques. Results show that 66% duty cycle RZ signal so-called the carrier-suppressed return-to-zero (CSRZ) format has the best performance in the intensity modulations. In phase modulations, the most outstanding modulation is DPSK. DQPSK modulation is also a very promising choice if the effect of noise could be resolved. The combination of intensity modulation and phase modulation will compromise the performance advantages of both.