Experimental study of depolarization of laser radiation by fiber optic elements

At present, in polarization-based optical fiber sensors the optical fiber is used both as a sensitive element (SE) and as fiber-optic communication lines (FOCL) for transmission of an optical signal. In such sensors, the polarization axes of the optical radiation source (ORS) and SE need to be aligned. However, FOCL elements located between the ORS and SE introduce their own polarization distortions due to the anisotropy of the optical properties of the fiber resulting from bending deformations of a random nature. This leads to a decrease in the accuracy and repeatability of the polarization sensor (PS) measurements. The proposed method of polarization correction consists in depolarization (transformation into circular polarization) of optical radiation by placing coils with an optical fiber between the ORS and SE, and certain parameters: the diameter of the coil, the number of turns and the angle of rotation of the coil relative to the plane of polarization of the ORS. This method allows one to exclude from the optical setup expensive optical elements (for example, quarter-wave plates) and simplify the design of the sensor / measuring device. In the course of experimental studies it was found that in this way it is possible to reduce the polarization distortion from the initial 17 dB to 1.6 dB.