Analytical research on walk-off, delay and peak power of control pulse in NOLM de-multiplexer

Impacts of walk-off, initial time delay and peak power of control pulse on the characteristics of NOLM de-multiplexer are studied in this paper. Walk-off between control pulse and signal pulse makes the NOLM de-multiplexer switching window deviate from the center position, and the transmittance also be decreased. It is researched that for a given walk-off, there is a critical value of initial time delay and peak power of control pulse respectively which ensures the switching window profile relocates at the center and the switching efficiency is 1.To take Gaussian pulse shape for example, for a given walk-off d, the switching window can be relocated at the center position by setting the initial time delay T_d = -Ld / 2 between control and signal pulse. That Optimum peak power of control pulse should be P_c = |d|√π/(2γ_sT_c|erf(Ld/2T_c)|) to obtain 100% transmittance for the NOLM de-multiplexer. The optimum peak power increases with the walk-off parameter, and is lowest for the case without walk-off. The numerical results show that, with walk-off between control and signal pulse, the switching window is flattened and broadened with the optimum initial delay and peak power of the control pulse. It is on one hand desirable to tolerate timing jitter between the control and signal pulses, but broadened switching window is likely to cause crosstalk of neighboring channel to the targeted demultiplexed channel on the other hand. So overmuch walk-off should be avoided.