Curvature sensor based on fiber ring laser with Sagnac loop

Abstract

Abstract In this paper, a curvature sensor based on fiber ring laser with Sagnac loop is proposed and experimentally demonstrated. The Sagnac loop is inserted into a fiber ring laser used as the sensing element and the filter. The intracavity sensing is induced in the fiber laser with the filtering characteristic of the Sagnac loop modulated by the curvature. The intracavity sensing system is used to narrow the corresponding 3-dB band-width and enhance the resolution of the curvature sensor. With the intracavity intensity modulation method, the output power of the fiber ring laser sensor will change with an increase in curvature. The curvature range from 0 m−1 to 5.6865 m−1 has been measured and the highest curvature resolution of 6 × 10−8 m−1 is obtained. Based on the intracavity sensing system, the curvature resolution level has been enhanced from 10−4 m−1 to 10−8 m−1. The stability and measurement errors of the system are also studied and analyzed.