High sensitivity optical fiber temperature sensor based on Fabry-Perot interferometer and enhanced vernier effect Available to Purchase

The purpose of this paper is to design a high-sensitivity temperature sensor based on the vernier effect (VE) of dual-parallel Fabry-Perot interferometers (FPIs).

Initially, ultraviolet (UV) glue is coated on the end-face of a smooth single-mode fiber (SMF) and then tapered using a charged coupled device (CCD) precision displacement platform. Once the UV glue solidified, it is cut flat with a cutting tool to create FPI₁. Subsequently, an SMF with a smooth end-face is inserted into a ceramic ferrule, and the other end-face of the ceramic ferrule is coated with polydimethylsiloxane (PDMS) to form FPI₂ and FPI₃. By adjusting the distance between the end-face of the SMF and the end-face of the ceramic ferrule, FPI₂ and FPI₃ are made to have different cavity lengths and free-spectral ranges (FSRs). In addition, the FSR of FPI₂ is approximately equal to that of FPI₁, while the FSR of FPI₃ is roughly twice that of FPI₁. When the temperature increases, the interference spectral lines of FPI₁ gradually red-shift, whereas those of FPI₂ and FPI₃ gradually blue-shift. The parallel combination of FPI₁ and FPI₂ results in an enhanced traditional vernier effect (TVE), and the parallel combination of FPI₁ and FPI₃ leads to an enhanced harmonic vernier effect (HVE).

Experiments demonstrate that the temperature sensitivity of FPI₁ is 0.17 nm/°C. The temperature sensitivities of FPI₂ and FPI₃ are −0.46 nm/°C and −1.90 nm/°C, respectively. Within the 30–37 °C temperature range, the enhanced traditional vernier effect sensor S₁, formed by the parallel connection of FPI₁ and FPI₂, attains a temperature sensitivity of 9.42 nm/°C. The enhanced harmonic vernier effect sensor S₂, constructed by the parallel combination of FPI₁ and FPI₃, reaches a temperature sensitivity of −29.59 nm/°C, respectively. These sensitivities represent a significant improvement over those of a single FPI.

These experimental results validate that the enhanced VE and the enhanced HVE represent an effective approach for enhancing sensor sensitivity. Moreover, compared with the enhanced VE, the enhanced HVE exhibits a more pronounced impact.