Improvements to the standard theory for photoreceiver noise

Abstract

The standard theory for photoreceiver noise unrealistically defines the system transfer function solely in terms of the input and output pulse shapes, based on the assumption that equalization is provided at the receiver output. Most photoreceivers reported in the literature, however, are only front ends and do not include equalizers, making direct application of the conventional noise expressions inappropriate. Even if equalization is provided, a signal-dependent definition of the transfer function will be accurate only under certain limited conditions. Furthermore, it is unrealistic to assume a given pulse shape at the input. In this paper we consider the effect of incorporating a more realistic transfer function into the conventional noise theory. We choose the transimpedance amplifier for our analysis due to its widespread popularity; however, our approach is general and can he applied to a broad class of photoreceivers. Since our transfer function is based on a physical circuit, our results can be used to estimate photoreceiver noise performance without making any assumptions on the input or output pulse shapes. >