Abstract

The signal-to-noise ratio of an optical heterodyne receiver degrades if the signal and local oscillator optical fields are not linearly polarized along the same axis. This paper presents direct detection and heterodyne detection schemes for tracking the axis of linear polarization in the signal beam. It gives an analysis of the error performance of the polarization tracking loop when it is operating at low signal powers and in the presence of background radiation, detector dark current, and thermal noise. The analysis includes a discussion of loop optimization and loop performance in the nonlinear (large error) region. Finally, experimental results for a direct detection scheme are presented.

© 1985 Optical Society of America