Patent ID: 7307722
Filing Date: 2007-12-11
Classification: G02F

Abstract:
1. A polarization stabilizing device for stabilizing the state of polarization of an optical signal having an arbitrary time variable polarization state and an input power, comprising: a retarder pair comprising first and second variable retarders operable to provide respective first and second phase retardations to the optical signal, wherein the first and second variable retarders have respective eigenaxes oriented at approximately ±45 degrees relative to each other; an optical element arranged to receive the optical signal from the second variable retarder and having an azimuth extending approximately parallel or perpendicular to the first variable retarder so as to pass a polarized component of the optical signal containing a fraction of the input power; a detection arrangement for obtaining a measurement signal indicative of the fraction of the input power of the optical signal contained in the polarized component; and a controller connected to receive the measurement signal, and connected to supply first and second control signals to the first and second variable retarders, wherein the controller is configured to set the first and second control signals responsive to the measurement signal so as to maintain the fraction of the input power in the polarized component at a target value, and wherein the controller is further configured to use the first control signal to commute the first phase retardation between first and second values so as to cause a commutation of the polarization state transmitted by the second variable retarder between two diametrically opposite positions on a Poincaré sphere.