Inline Microcavity-Based PCF Interferometer for Refractive Index and Temperature Sensing

We report an inline Fabry-Perot interferometer based on photonic crystal fiber (PCF) with microcavity as refractive index and temperature sensor. The interferometer consists of a section of large mode area PCF spliced with single mode fibers on one side, whereas a microcavity is fabricated on the other side of PCF. The formation of the microcavity reduces the period of the interference pattern thereby providing distinctiveness to the measurement. Experimental results show that this simple, compact, and highly stable inline interferometer has temperature sensitivity of 12 pm/°C and a refractive index sensitivity of ~30 nm/RIU along with a resolution of 3 × 10^-4 RIU^-1.