High performance semiconductor optical amplifiers (SOAs) and applications

Summary form only given. Over the last five years, the performance of semiconductor optical amplifiers (SOAs) has improved considerably. In this paper, the parameters of importance for characterizing SOAs are introduced and their significance in characterizing fiber links performance are pointed out. In particular, the gain, the concept of signal-to-noise ratio at the input and output of the amplifier, the overall noise figure of an SOA, the saturation power, the electrical and optical signal-to-noise ratios are discussed. This paper also demonstrate how SOAs can get around the thermal noise limit of standard optical p-i-n detectors/pre-amplifiers and reach an optimal sensitivity of 44.5 photons per bit at a bit-error-rate (BER) of 1 × 10^-9, despite the degradation caused by spontaneous-emission noise.