Doublet-waveplate polarization transceiver system for backscattering suppression in laser communication terminal

Abstract

The backscattering suppression capability of the optical signal transceiver is the key to establish a single wavelength full-duplex bidirectional laser communication link. When the signal is transmitted and received through the same telescope of the laser communication terminals, stray light from the high-power laser on mirrors will be received by the high-sensitivity detector, affecting the sensitivity of the system. In this paper, the polarization modulation characteristics of scattered light by the mirrors with different roughness are analyzed. The traditional system based on polarization splitting and transmitting with a single quarter waveplate is improved by using a doublet waveplate, i.e., a combination of a half waveplate and a quarter waveplate. The transceiver system including the off-axis optical antenna is developed and the signal transceiver isolation (ability of suppressing backscattering light) is improved by 7∼8 dB. Although the system complexity is increased, the waveplate can work as a solar window to improve the environmental adaptability. The laser communication terminal would meet the requirements of further link communication, including inter-satellite networks under the same aperture condition.