Design And Sensing Characteristics Of Interferometric Sensor Based On Photonic Crystal Fiber

Photonic crystal fibers have attracted much attention in the field of fiber sensing and nanophotonics due to its high birefringence coefficient,low loss and dispersion adjustability.The sensor based on photonic crystal fiber has higher sensitivity compared with traditional physical sensors.The Mach-Zehnder interference version and the vernier effect version were designed and fabricated based on the light field distribution and optical transmission characteristics of photonic crystal fiber.Additionally,the sensing characteristics of parameters such as temperature,humidity,refractive index and gas pressure were investigated.The full-vector finite element method was used to theoretically explore the air hole and the properties of photonic crystal fiber,and the numerical analysis was developed through simulation.The optical field distribution of the crystal fiber was calculated,and the cladding effective refractive index of the photonic crystal fiber was 1.451 which was consistent with the LMA-10 photonic crystal fiber used in the experiment.Combined with the sensor sensing theory,the relationship between the effective refractive index difference of the Mach-Zehnder sensing region and the sensing sensitivity,and the relationship between the parameters of Fabry-Perot cavity and the sensing sensitivity were obtained.The Mach-Zehnder interference photonic crystal fiber sensor was fabricated by the collapse welding of single-mode fiber and photonic crystal fiber.The Mach-Zehnder interference was obtained by using the collapse region as the excitation region.The temperature and refractive index sensing system was built in the experiment.The temperature and refractive index sensing characteristics of the sensor were studied.The obtained temperature sensitivity and refractive index sensitivity were 122 pm/°C and-14.66 dB/RIU,respectively.A graphene-coated humidity sensor was prepared and the humidity sensing characteristics experiments was carried out,and the obtained humidity sensitivity was 53.86 pm/%RH.In order to improve the sensitivity,a photonic crystal fiber sensor with vernier effect was prepared by the non-collapse fusion of single mode fiber,quartz tube and photonic crystal fiber.The temperature and barometric sensing system was built to study the temperature and pressure sensing characteristics of the sensor.The temperature sensitivity and barometric sensitivity were found to be 140 pm/°C and-29.99 nm/MPa,respectively.