A polarization-maintaining fiber loop mirror based sensor for liquid refractive index absolute measurement

A fiber sensor based on polarization-maintaining fiber loop mirror (FLM) for liquid refractive index absolute measurement is described. Two sections of polarization maintaining fibers (PMFs) with different length were inserted into the FLM. One section of PMF was chemical etched for liquid refractive index measurement and the other one for reference. Liquid refractive index absolute measurement can be obtained by detecting the interference wavelength difference corresponding to the two sections of PMFs. High sensitivity of 63.82 ± 0.04 nm/RIU (refractive index unit) and a resolution of 3.14 × 10−4 RIU were obtained for the proposed liquid refractive index sensor.