Optimization of InP APDs for high-speed lightwave systems

Calculations are carried out to optimize the width of the InP avalanche region in high speed APD-based optical receivers. The model includes the effects of intersymbol interference, tunneling current, avalanche noise and its correlation with the stochastic avalanche duration. A minimum sensitivity of ~-27.9 dBm is predicted at an optimal width of ~0.17 mum and an optimal gain of approximately 9, for a 10 Gb/s communication system, assuming a Johnson-noise level of 500 noise electrons per bit. The factors controlling the optimum sensitivity are confirmed. Results show increased tunneling current results in increasing receiver sensitivity, as device width decreases below its optimum value. As device width increases above its optimum, the receiver sensitivity increases as device bandwidth decreases; and dominates over increasing excess noise.