Temperature-insensitive strain sensor using a fiber loop mirror based on low-birefringence polarization-maintaining fibers

A temperature-insensitive strain sensor by using a fiber loop mirror (FLM) based on low-birefringence polarization-maintaining fibers is described. Two equal-length polarization maintaining fibers (PMFs) with different birefringence indices were inserted into the FLM. One PMF was used for strain measurement and the other for temperature compensation. High sensitivity of 3.5 pm/με (ε is the unit of strain) and resolution of 5.7 με have been achieved for the proposed strain sensor. The temperature cross sensitivity for the proposed strain sensor is only 0.094 με/°C which satisfied well with the theoretical derivation.