New Scheme of Sagnac Interferometric Fiber-Optic Current Sensor Insensible to Mechanical Vibration

A new scheme of Sagnac interferometer fiber-optic current sensor insensible to mechanical vibration is presented. This scheme eliminates the Sagnac effect, which is responsible for the sensitivity to vibration according to theoretical analysis with Jones matrix. The improvement to the conventional Sagnac interferometer fiber-optic current sensor is achieved by changing the structure of sensing fiber coil. This coil is fabricated by the bifilar winding technique, and it consists of one half-wave plate embedded in the middle of sensing optical fiber and one quarter-wave plate rotated by 90 degrees in its lower input port. Experimental results suggest that, compared to the conventional design, this new-structured Sagnac interferometer fiber-optic current sensor has much better performance against strong mechanical vibration at accelerations up to 20 g and frequencies from 10 to 400 Hz. Furthermore, the current measurement accuracy of the improved fiber-optic current sensor achieves the 0.2-level at an acceleration of 20 g and a frequency of 150 Hz.