High stability Michelson refractometer based on an in-fiber interferometer followed with a Faraday rotator mirror

•Two main problems of reflection interference spectrum stability and power loss of in-fiber Michelson refractometers are improved.•A high stability Michelson refractometer based on an in-fiber interferometer followed with a Faraday rotator mirror (FRM) is proposed and demonstrated.•Spectrum stability and light power loss reduction are obtained in the sensor. We demonstrated an optical fiber refractive index (RI) sensor based on an in-fiber Michelson interferometer (MI), which is fabricated by splicing a Faraday rotator mirror (FRM) to a singlemode-thin core-singlemode (STS) optical fiber interferometer. From our experiments, it can be found that thus a FRM as reflector can eliminate the polarization random fluctuation of interference spectrum, which makes the sensor exhibit a high stability. Core to core splicing of thin core to standard single mode optical fibers and high reflectivity mirror of FRM can reduce the optical power loss and improve the fringe contrast of sensor spectrum. Both high stability and low power loss are very important in such kinds of reflection interference spectrum modulation and high resolution sensors. This sensor wavelength and intensity RI sensitivity is −48.858nm/RIU and −6.548dB/RIU at the liquid RI from 1.38 to 1.435, respectively. The temperature sensing performance of this sensor is also studied, the sensor wavelength versus temperature sensitivity is 66.18pm/ °C and intensity hardly change with temperature, which means that the temperature cross sensitivity can be eliminated when intensity modulated, and this sensor also has compact size, simple structure, easy fabrication and good repeatability.