Air cavity-based Fabry–Perot interferometer sensor fabricated using a sawing technique for refractive index measurement

Abstract

We have demonstrated a refractive index sensor based on a fiber optic Fabry–Perot (FP) interferometer with an open air cavity fabricated using a one-step mechanical sawing technique. The sensor head consists of a short FP cavity near the fiber patch cord tip, which was assembled by joining a ceramic ferrule and a single-mode fiber together. Owing to the open air cavity in the sensor head, various liquid samples with different refractive index can fill in-line air cavity, which makes the device usable as a refractometer. Moreover, due to the sensor head encircled with the robust ceramic ferrule, the device is attractive for sensing measurement in harsh environments. The sensor was tested in different refractive index solutions. The experimental result shows that the attenuation peak wavelength of the sensor is shifted toward a shorter wavelength with increasing refractive index, and the refractive index sensitivity is ∼92.5 nm/refractive index unit (RIU) and 73.75 dB/RIU . The proposed sensor can be used as an in-line refractometer for many potential applications in the sensing field.