Large temperature sensitivity of fiber-optic extrinsic Fabry–Perot interferometer based on polymer-filled glass capillary

A novel and low cost fiber-optic extrinsic Fabry–Perot interferometer (EFPI) is proposed. The EFPI is fabricated at the fiber tip by inserting a single mode fiber (SMF) into a partially polymer-filled glass capillary to form an air micro-cavity, which can be precisely controlled with a three-dimensional translation stage. The optimal EFPI has a loss less than 10 dB and a fringe visibility more than 30 dB. Application of the EFPI for temperature measurement is experimentally demonstrated. Due to the high thermal expansion coefficient (TEC) of the polymer, the sensor exhibits a good linear response and large temperature sensitivity of ∼5.2 nm/°C, which is almost three orders larger than that of the current F-P temperature sensors. Therefore, it may be applied to the surrounding temperature sensing.