EFFECTS OF CROSSTALK AND TIMING JITTER ON ALL-OPTICAL TIME-DIVISION DEMULTIPLEXING USING A NONLINEAR FIBER SAGNAC INTERFEROMETER SWITCH

All-optical time-division demultiplexing using a nonlinear fiber Sagna c interferometer switch (NSIS) is studied with respect to the two main causes that degrade the bit-error-rate (BER) performance: crosstalk a nd timing jitter. It is shown that unwanted cross-phase-modulation in the reference signal which counter-propagates to the control pulse, as well as the poor extinction of the switch itself, seriously degrades the extinction ratio of the switch, thus increasing the crosstalk from other channels. Numerical calculations clarify the effect of the swit ching window width, window shape, and the multiplexed channel number o n the power penalty in terms of BER performance, Timing jitter between the signal and control pulses is investigated as another degradation factor that causes an error floor in BER performance, It is found that the minimum BER is obtained when the window width is set to the time slot width and the rms value of the jitter must be less than 1/14.1 ti mes the time slot width to ensure that BER < 10(-12). To confirm this analysis, precise measurements of BER performance with NSIS-based demu ltiplexing are performed using amplified gain-switched laser diode pul ses, as the relative timing jitter, switching window width, and multip lexed channel number are varied, Good agreement with the analysis is s hown. Finally, optimum system design based on a small power penalty an d low error door is described, It is shown that the NSIS has the poten tial of demultiplexing a 160-Gb/s or 320-Gbis optical data stream into its 40-Gbis constituents with only a 4-dB or 7-dB power penalty,