Optical distribution of microwave signals for Earth Observation satellites

Optical distribution of signals is playing a key role in ESA Earth Observation satellite SMOS (Soil Moisture and Ocean Salinity). This paper is describing a possible evolution of the optical harness in which the Local Oscillator, the calibration microwave signal and the clock reference are distributed in a single fiber thanks to Wavelength Division Multiplexing (WDM). Due to the high sensitivity of the on-board RF Front-ends, degradation effects induced by the optical link can severely affect the overall performance. Therefore, system level requirements like signal isolation or phase noise are to be taken into account. Preliminary test measurements have shown that isolation over 70dB can be obtained in the RF domain. This study is a first step towards the fully distribution of signals through optic fiber in SMOS-like missions.