High sensitivity fiber optic ultraviolet light and temperature sensor based on Fabry-Perot cavity fabricated by MA-POSS material

In order to meet the demand for high-sensitivity UV light detection in industrial production, a novel Ultraviolet (UV) light and temperature sensor based on Fabry-Perot interferomwter (FPI) and harmonic vernier effect is proposed. Firstly, the MA-POSS liquid is dropped into the gap between two aligned single-mode fibers (SMFs), and then the MA-POSS is irradiated with UV lamp for more than 10 s. After liquid curing, a MA-POSS based FPI is made and named FPI₁. When FPI₁ is irradiated with UV light, the refractive index of MA-POSS changes and it expands along the longitudinal line, resulting in linear drift of the resonant wavelength of FPI₁. The UV light intensity is obtained by demodulating the resonant wavelength of FPI₁. Additionally, MA-POSS also has good thermal sensitivity, so FPI₁ is highly sensitive to temperature. To further enhance sensitivity, a reference FPI₂ was prepared by sequentially fusion splicing SMF - capillary - SMF, resulting in a free spectral range of only about half of FPI₁. When FPI₁ and FPI₂ are cascaded, they form a first harmonic vernier effect sensor S₁. The experimental studies have found that the sensitivities of UV light intensity and temperature of FPI₁ are 9.6 pm/(mW/cm²) and 133.1 pm/°C respectively, and the sensitivities of UV light intensity and temperature of S₁ are −396.5 pm/(mW/cm²) and −4.6277 nm/°C respectively. S₁ amplified the UV light intensity and temperature sensitivity of FPI₁ by 42.4 and 35.3 times respectively. In summary, the proposed sensor can achieve high sensitivity measurement of UV light intensity and temperature simultaneously, and the sensor structure is simple, compact, easy to manufacture, and robustness. It will become one of the strong competitors in UV intensity detection.