Manufacturing Method and Stability Research of the Fiber Quarter-Wave Plate for Fiber Optic Current Sensor

One of the most important elements of the optical scheme of the fiber-optic current sensor is a quarter-wave plate, which converts two orthogonal linearly polarized modes into circularly polarized modes, which propagate further in the sensitive element of the sensor. To maintain the integrity of the system and ensure high-precision measurements, it is important that the plate is made of fiber, and its length is equal to a quarter of the beat length with an accuracy of a hundredth of a millimeter, which is technically very difficult to achieve. This article discusses a model of an electronically adjusted quarter-wave plate, which made it possible to check the operability of the fiber-optic current sensor circuit. The article also describes a method for manufacturing of quarter-wave plate, presents the results of temperature tests of plates of different lengths in the current sensor circuit, and estimates the effect of the quarter-wave plate temperature on the measurement error.