Compact Highly-Sensitive Temperature and Refractive Index Sensing Fiber Probe Based on PDMS Fabry–Perot Cavity With Controllable Curvature Radius

In this paper, a highly sensitive optical fiber temperature and refractive index dual parametric sensor based on Fabry-Perot (F-P) interference is proposed. The sensor is fabricated by fusing a section of hollow core fiber (HCF) to a single mode fiber (SMF) and filling the HCF with polydimethylsiloxane (PDMS). The F-P cavity length and the curvature radius of the reflective surface of the cavity can be precisely controlled. The effects of the cavity length and the curvature radius on the sensing property are investigated in detail. Five sensors with different parameters are fabricated, and their refractive index sensing properties in the refractive index range of 1.3350-1.3795 and temperature sensing properties in the temperature range of 36<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula>C-41<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula>C are tested experimentally. The long-time operating stability of the sensors is also tested. The results show that our sensors have the advantages of high sensitivity, easy demodulation, and good stability, and may have promising applications in the detection of body temperature and the refractive index of biological solution, blood, etc.