Refractive Index and Temperature Sensing with Sagnac-Mach Zehnder Hybrid Fiber Interferometer

A high-sensitivity, large dynamic range refractive index and temperature sensor based on a hybrid fiber interferometer is proposed and demonstrated. The exposed-core fiber is highly birefringent due to its asymmetric structure and also supports multimode propagation, thus can be used simultaneously as a Mach-Zehnder and Sagnac interferometer. The sensor can be used for resolving the problem of trade-off between high sensitivity and large dynamic range. In addition, the sensor can potentially be used for achieving simultaneous measurement of temperature and refractive index due to their different sensitivities to these parameters.