On the simulation of digital optical links with EDFA's: an accurate method for estimating BER through Gaussian approximation

A new method for the semi-analytical estimation of the bit-error rate (BER) of digital optical systems is presented. It is based on system simulation and accurately considers the performance degradation caused by waveform distortion. The method profits from the simplicity of Gaussian approximation for noise statistics, though explicitly accounting for intersymbol interference (ISI) effects in noise during the BER estimation. Optically preamplified and avalanche photodiodes (APD) receivers are considered, for which signal-dependent noise components are dominant. The system parameters influence on receiver sensitivity is studied. A digital optical transmission link with a single in-line erbium-doped fiber amplifier (EDFA) and with an EDFA chain is then analyzed. The influence of the EDFA chain characteristics on system performance is investigated: amplifier gain, noise figure and spacing are considered. The tradeoffs between EDFA parameters and system optimization are addressed.