Temperature Compensated Highly Sensitive Refractive Index Sensor Based on Mach-Zehnder interferometer and FBG

Abstract

ABSTRACT We propose and demonstrate a temperature compensated highly sensitive refractive index (RI) sensor based on Mach-Zehnder interferometer (MZI) cascaded with a fiber Bragg grating (FBG). The MZI is fabricated by inserting a segment of tapered single mode fiber (TSMF) in between two sections of multi-mode fiber (MMF), interference happens between the beams travelling in and around the TSMF. Due to the RI difference of between the silica and external RI around the TSMF is much larger than that between the core and cladding of the TSMF, it also can be called as a two-beam interferometer. Experimental results show that the MZI (S1) with RI and temperature responses of -3244.22\xa0nm/RIU (Air-RI), -14296.23\xa0nm/RIU (Liquid-RI) and 35.18\xa0pm/℃ respectively. The FBG exhibits a temperature response of 12.25\xa0pm/℃ and shows insensitive to RI. Ascribing to the MZI and FBG have different responses to variations in RI and temperature, solving the temperature crosstalk of RI sensor.