Dependence of the Signal-to-Noise Ratio for a Mixture of Coherent and Incoherent Sources on the Incoherent Source Spectral Profile

A semi-classical theory of photodetection noise for an optically amplified signal has been obtained and the explicit dependence of the photovoltage variance on the incoherent source spectral profile has been identified. The theoretical predictions have been compared with experimental results measured using a digital sampling oscilloscope for cases of a coherent source, an incoherent source, and a mixture of coherent and incoherent sources.