High sensitivity Sagnac interferometric temperature sensor using stress region refractive index modulation

An all-fiber temperature sensor employing intentional refractive index modulation is experimentally demonstrated. The sensor consists of four sections of polarization maintaining fiber (FPMF) sandwiched between multi-mode fiber (MMF). The stress region of two sections of polarization maintaining fibers (PMFs) is aligned and then anti-clockwise rotates one PMF in 10 deg angles while the other keeps still. Finally, the discharge proceeds. The remaining two PMFs are fusion spliced with the same method. Then the prepared FPMF-MMF structure is connected to the 3 dB coupler to construct a Sagnac loop. The temperature sensitivity reaches 1.49 nm/°C for a temperature range from 16°C to 55°C. The proposed temperature sensor with easy fabrication and good linearity in measuring temperature can be a promising candidate for various applications in environmental monitoring and industrial production.