Ring-Down Technique Using Fiber-Based Linear Cavity for Remote Sensing

This article presents a fiber cavity ring-down (CRD) technique using a linear cavity configuration for remote sensing. The proposed scheme is based on a single fiber coupler of 99:1 and two thin-film mirrors located at the end of the fiber arms. The use of an optical time-domain reflectometer as both input and output sources allows interrogation of the output signal in reflection. Remote sensing is demonstrated in a maximum fiber length of 10 km. A proof-of-concept for strain sensing is demonstrated. As a proof-of-concept, a fiber Bragg grating was used inside the cavity, acting as both a mirror and a strain sensor. This linear CRD scheme allows the use of different types of fiber mirrors, which can also be used as sensor elements, thus featuring remote sensing in a compact and simple configuration.