Polarization control on output of single-mode optical fibers

Polarization control of the light output from single-mode fiber systems is very important in order to connect it to polarization-dependent integrated optical circuits and applications using a heretodyne detection system. In this paper, automatic control of the polarization of light transmitted through the fiber was demonstrated by an electrooptical and electrical feedback system. In this system, we used a 1.6 μm long wavelength semiconductor CW BH laser, low-loss single-mode optical fiber with a loss of 0.2 dB/km, and two thinz-cut LiNbO3modulators tilted 45° relative to each other. The output light from this polarization controller was maintained to be linear while that from the single-mode fiber was unstable and elliptically polarized.