Ultrafast optical time division multiplexing/demultiplexing using nonlinear Fabry-Perot etalons

One factor limiting interest in optical bistable devices is their relatively slow speed. For example, GaAs/AIGaAs MQW nonlinear etalon devices have switch-on times of 1 ps 1 but switch-off times in excess of 150 ps. 2 Similarly, ZnS and ZnSe thermal etalons can switch on more quickly than they switch off because of slow thermal relaxation times. This places a revere restriction on rates of operation. To circumvent this problem, we propose the use of nonlinear etalons in an optical time division multiplexing/demultiplexing system and describe a transmitter (two nonlinear etalons and an optical delay line) that can produce optical pulses as short as the etalon switch-on times. Pulses from the transmitter for each channel are coupled in a time sequence into a waveguide. The process is repeated after the etalon carrier-recombination (thermal relaxation) time has elapsed. Demultiplexing is carried out in a similar way. Etalon time division multiplexing results in bit rates much larger than possible for individual devices. For GaAs/AIGaAs etalons with 150-ps recombination times, bit rates from 6.7 to 500 Gbit/s should be obtainable, depending on the number of channels used. We experimentally demonstrate the feasibility of the multiplexing and demultiplexing schemes using ZnS thermal etalon devices.