Optical fiber refractive index sensor based on peanut flat-end reflection structure

An optical fiber peanut flat-end reflection refractive Index sensor based on Michelson interference principle is experimentally demonstrated. It has one peanut structure which makes it easy to fabricate and can implement measurement on the same side. The peanut structure is fabricated by electrical arc discharge. This structure constitutes a Michelson interferometer. Experimental results show that the relationship between the refractive index of the tested solution and the extinction ratio of the interference spectrum is a quadratic function, the fitting degree is 0.9915, and the refractive index measurement range is from 1.34 to 1.43. In the measurement range of refractive index from 1.34 to 1.43, its measurement sensitivity decreases with the increase of the refractive index of tested solution, when refractive index is 1.34, the maximum measurement sensitivity is 197.872 dB while the minimum measurement sensitivity is 9.394 dB when the refractive index is 1.43.