Fiber Bragg grating Fabry-Perot Interferometer in multicore fiber for refractive index measurements

A fiber optic refractive index sensor based on Fabry-Perot interferometer formed by two Chirped Fiber Bragg Gratings on a seven-core fiber is successfully demonstrated. A small part of the fiber cladding is etched to expose the outer 6 cores to the ambient environment. While optical modes supported by the outer 6-cores are affected by both temperature and refractive index changes of the surrounding liquid, the optical mode in the central core is affected by the temperature changes only. Because only a small part of the cladding is removed, the sensor maintains excellent mechanical strength and stability.