An ultra-high-resolution large-dynamic-range fiber optic static strain sensor using Pound-Drever-Hall technique

In this paper we report the realization of a fiber optic static strain sensor with ultra-high resolution and large dynamic range for the applications of geophysical research. The sensor consists of a pair of fiber Bragg grating based Fabry-Perot interferometers for strain sensing and reference, respectively. Pound-Drever-Hall technique is employed to interrogate the sensor heads, and a cross-correlation algorithm is used to figure out the strain information with high precision. Static strain resolution down to 4.5 nε was demonstrated. The dynamic range can be extended up to hundreds of με, and the measuring period is a few tens of seconds.