SIMULATION OF 12.5 GB/S LIGHTWAVE OPTICAL TIME-DIVISION MULTIPLEXER USING SEMICONDUCTOR OPTICAL AMPLIFIERS AS EXTERNAL MODULATORS

Using computer simulation techniques, a nonlinear model is developed for the use of traveling-wave semiconductor optical amplifiers as external modulators for multiGb/s OTDM lightwave systems. The simulation results indicate that the modulation performance is sensitive to the precise time delay between the incident optical pulse and the electrical injection current pulse required to drive the TWSOA external modulator. It is found that satisfactory modulation performance is obtained when the peak of the input optical pulse p(in)(t) coincides with the trailing edge of the injection current pulse I(t). The simulation results then indicate that under this condition, adequate modulation performance at 2.5 Gb/s per channel, over a practically useful range of input signals, is possible provided that - 10 dB less-than-or-equal-to E(in)/E(sat) less-than-or-equal-to 0 dB. It should be added that at the given pulse width used in our simulation (almost-equal-to 80 ps at the base line), the multiplexed bit rate can be as high as 12.5 Gb/s in our proposed OTDM system, if the pulse spacing is adjusted for the maximum multiplexed bit rate.