Measurement of high temperature by using a fiber interferometer based on a photonic crystal fiber

We demonstrated the performance of a fiber sensor based on a photonic crystal fiber (PCF) for the detection of high temperatures. The proposed fiber sensor was implemented by collapsing the air holes of the PCF with an arc discharge and forming an in-fiber Mach-Zehnder interferometer. The intentionally collapsed parts in the PCF cause coupling between the core mode and the cladding modes, which produces interference fringes in the transmission spectrum. The spectral response was observed while changing the ambient temperature. The fiber sensor operated properly at high temperatures up to 1000 .deg. C. The proposed fiber sensor presented good reliability after repeated temperature variation cycles and showed low hysteresis over wide temperature range. We expect this compact fiber sensor to be applied to monitoring the high-temperature distribution around a thin film sensor and to be an alternative for a strain/pressure thin film sensor under high temperatures in harsh conditions.