Satisfactory operation of a dual beam laser Doppler anemometer system requires that the maximum fringe contrast is achieved. This implies, in turn, that the two intersecting beams should have the same intensity and the same state of polarization. This requirement is achieved in many systems by careful adjustment of the polarization state, often at the time when the laser Doppler anemometer system is first aligned. The present paper describes a compact and relatively cheap device that enables the polarization of the light transmitted through a step index mono-mode optical fiber to be controlled. Design methods for this device are discussed and a prototype opto-mechanical system is described. Finally, some experimental data are presented from which the performance of the device in adjusting the polarization of a laser beam can be assessed. (C) 2021 Optical Society of America
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