Core Mode-Cladding Supermode Modal Interferometer and High-Temperature Sensing Application Based on All-Solid Photonic Bandgap Fiber

A core-mode-cladding-supermode modal interferometer with all-solid photonic bandgap fiber (AS-PBF) is constructed, and a reflective Michelson-type high-temperature sensor is fabricated. Such a fiber sensor is constituted by a small segment of AS-PBF and a leading single-mode fiber. The splice region of the two fibers is weakly tapered to excite the cladding supermode. Both the interference spectra and the near-field infrared CCD images verify that the LP01 cladding supermode is effectively excited and interferes with the LP01 core mode, which agrees well with theoretical results. Benefiting from a large effective thermooptic coefficient between the two modes, temperature sensitivity up to 0.111 nm/°C at 500 ^°C is obtained in experiment. The proposed sensor is compact and easy to fabricate, which makes it very attractive for high-temperature sensing applications.