Fiber Mach-Zehnder interferometer based on microcavities for high-temperature sensing with high sensitivity

A high-temperature sensor based on a Mach-Zehnder interferometer (MZI) in a conventional single-mode optical fiber is proposed and fabricated by concatenating two microcavities separated by a middle section. A femtosecond laser is used to fabricate a microhole on the center of a fiber end. Then a micro-air-cavity is formed by splicing the microholed fiber end with a normal fiber end. The interferometer is applied for high-temperature sensing, in the range of 500-1200 degrees C, with a sensitivity of 109pm/degrees C that, to the best of our knowledge, is highest in silica fiber temperature sensors. Also, the interferometer is insensitive to external refractive index (RI), which is desirable for temperature sensors. (C) 2011 Optical Society of America