Abstract

In this paper, a coherent optical polarization azimuth modulation (POLAM) system is proposed¹ for space communication and its system performance is theoretically analyzed. This analog coherent optical space communication system can perfectly remove the unavoidable phase noise generated from the high power laser diode. The polarization azimuth means the polarization direction deciding the state of polarization (SOP) of light. As the SOP of light is essentially independent of the absolute phase of each orthogonal polarization component, the SOP is never affected by any phase noise in principle. In the free space channel without such a polarization dependency as in the optical fiber, we can make good use of the SOP of light as a modulation parameter in the coherent optical communication system. If we choose the SOP as a new modulation parameter, it is possible to establish the coherent optical space communication system insensitive to the phase noise. Therefore, our system is very useful in the presence of any phase noise.

© 1995 IEEE