Laser altimetry and deep space communications are two typical applications requiring very low noise optical receivers in
order to achieve detection of weak and short optical pulse. Avalanche photodiode is the detector of choice for its high
quantum efficiency, compact size, reduced electronics complexity and its ability to operate in a radiation-hard
environment. Optimal operating condition in terms of APD gain and temperature is the key to maximize the signal to
This paper describes the model and the measured performance of a hybrid optical receiver using a TE cooled Silicon
Avalanche Photodiode. Receiver performance in terms of responsivity and NEP will be presented as a function of
temperature, signal power and APD Gain. A brief discussion of radiation impact on noise is also presented. A NEP of
only 5fW/sqrt(Hz) has been obtained with a bandwidth of 200MHz in linear mode at a wavelength of 1060nm.