Fiber characterization for application in heterodyne laser interferometry, part II: modeling and analysis

For beam delivery in a single-fiber-fed heterodyne laser interferometer with nanometer uncertainty, the use of polarization-maintaining (PM) fibers is investigated. The PM properties of the light emerging from the fiber determine the achievable measurement accuracy. Measurements of the polarization-mixing properties of several different PM-fiber types as well as a range of fiber lengths were described in part I of this paper. In this part, a model and analysis of the fiber are presented. By means of the analytical model, a quick selection method is given, which can also be used to precisely align the fiber with respect to the other optical components of the interferometer. The presented model, based on Jones matrices, allows the investigation of local and global disturbances within the fiber and their location. As in part I, the dominant effect of the connector in the fiber assembly is shown. The effects of imperfections in fiber material are shown for longer fibers; they change the dominating connector effect slightly