High-Resolution Optical Fiber Salinity Sensor With Self-Referenced Parallel Fabry-Perot Fiber Microcavity

A high-resolution salinity sensorbasedon a self-referenced parallel Fabry-Perotfiber microcavity is proposed. The sensor is fabricated by inserting a short piece of exposed-core microstructure fiber (ECF) between multimode fiber (MMF) and single-mode fiber (SMF). Due to the unique exposed-core fiber structure and the specially designed SMF-MMF-ECF-SMF structure, two prominent parallel Fabry-Perot interferometers (FPIs) are constructed. Besides, a self-referenced differential phase-demodulation technology is proposed to eliminate thewavelength uncertainty of the spectra measurement devices. Enhanced demodulation system stability and accuracy are achieved by analyzing the phase shift responses of the reflection spectrum. A high salinity-phase sensitivity of 17.36 deg/% in the range from 0% to 35% is obtained, and the corresponding refractive index (RI) sensitivity is 1.04 x 10(5) deg/RIU. The salinity resolution and RI resolution are as low as 0.0058% and 9.6 x 10(-7) RIU, respectively, which gives a great potential for harsh environmental monitoring and label-free biochemical analysis.

Automated summary

A high-resolution salinity sensor based on a self-referenced parallel Fabry-Perot fiber microcavity is proposed. The sensor utilizes a specially designed fiber structure and differential phase-demodulation technology to achieve enhanced stability and accuracy. It demonstrates high salinity-phase sensitivity, low salinity and refractive index resolutions, making it suitable for harsh environmental monitoring and biochemical analysis.