Evaluation of the Inherent Ripple Effects on the Performance of an Optical DQPSK Signal Generated by Using Only One MZM

We analytically computed the optical spectra and numerically evaluated the ripple impacts on the performance of an optical DQPSK signal generated by only one MZM. We confirmed the necessity of a pulse carver to this kind of signal. The tolerances to the timing mismatch between the data and the pulse carver were analyzed among different duty-cycles. The conventional DQPSK signal generated by two parallel DPSK modulators were also analyzed for comparisons. We also provided some experimental results to demonstrate the possibility of the one-MZM scheme and the necessity of a pulse carver in terms of the clearly opened demodulated eyes.