Theory of direct-detection lightwave receivers using optical amplifiers

A simple theory is presented for analyzing the sensitivity and bit-error rate (BER) performance of direct-detection lightwave receivers using optical amplifiers. The analysis provides closed-form expressions for the BER and receiver sensitivity, and includes the impact of phase noise. Furthermore, the proposed theory predicts the optimum filter bandwidth values required for linewidths of practical interest (up to 100% of the bit rate). For the special case of zero linewidth, the average signal energy predicted by this work is 42.3 photons/b at BER=10/sup -9/. This result is within 0.47 dB of the sensitivity predicted by more accurate techniques.<
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