End-to-End Performance Analysis of Analog Coherent Optical Satellite Feeder Links

Optical feeder links (OFLs) benefit from the vast amount of bandwidth available in the THz-regime of the electro-magnetic spectrum, and could enable future terabit-per-second satellite systems. This study assesses the end-to-end performance of analog coherent OFLs for digital video broadcasting (DVB) applications, employing phase modulation (PM) and double-sideband suppressed carrier (DSB-SC). Though both PM and DSB-SC suffer from non-linear distortion, we show that with DSB-SC the optical modulation index can be reduced such that the modulator is operated in the linear regime, without sacrificing the signal-to-noise ratio (SNR). Using end-to-end simulations of a geostationary orbit (GEO) feeder link the Es/N0 penalty due to the optical feeder link (OFL) is determined. With typical system parameters and link losses the OFL-induced penalty remains below 1 dB, even under moderate turbulence conditions and APSK32 (8/9). As a result, the usual suspects, the RF traveling-wave tube amplifier (TWTA) and the RF user channel, remain the key limiting factors for the end-to-end performance.