Research Of Sensing Based On Photonic Band-Gap Fiber

Photonic crystal fiber （PCF） is a new type of microstructured fiber, it was firstly proposed in1992. Compared with traditional optical fiber, it has endless single-mode guiding, chromaticdispersion management, high nonlinearity and high birefringence. Since its inception, it has got alot of attentions. It has flexible structure and superior performance, and it can be filled withdifferent materials in the fiber air holes, such as liquid crystal, gas, high temperature-sensitive liquid,etc. Due to these performances, it can be made into a variety of high-sensitivity sensor pieces. Inrecent years, the research and application based on photonic crystal fiber sensing has become a hotspot.In this paper, the temperature sensing and gas sensing of photonic bandgap fiber are studied byusing the plane wave expansion method （PWM） and full vector finite element method （FEM）combined with computer software COMSOL. And a method of hollow-core photonic crystal fiberfor gas sensing is proposed. By designing of suitable anti-resonance ring thickness, the confinementloss of PCF and its core power ratio can be controlled. The numerical results show that whennormalized ring thickness T=5and wavelength λ=1.65372μm, the core power ratio is99.19%,confinement loss reaches1.48×10^-3dB/km. It further improves the core power ratio and reducesthe confinement loss in order to let HC-PCF better applied to gas sensing.A method of temperature sensing for photonic bandgap fiber is proposed. Full-vector finiteelement method is used to analyze the relationship at different temperatures between the effectivemode area Aeffand the temperature T. The impact of the size of the air hole diameter and holespacing on the characteristics of the temperature sensing is also discussed. The results show that thephotonic bandgap fiber filled toluene has a high temperature sensitivity, which can reach20.20dB/m/C.And the temperature sensitive interval can be adjusted through the design of differentstructural parameters.Finally, a brief introduction to the gas detection system based on hollow-core photonic crystalfiber is introduced. The basic principles and performance of the HC-PCF used in gas sensing is alsodiscussed.