Study On Structural Design,Fabrication And Characteristics Of Fiber Bragg Grating

Fiber Bragg Grating(FBG)is a passive photon component in an optical Fiber with spatial periodic refractive index distribution.The central wavelength of FBG reflectance spectrum drifts with external parameters,such as temperature,bending,strain,and so on.it is applied in various fields of sensor monitoring,and all kinds of grating sensors are faced with the problem of temperature cross-sensitivity.Twin-core Fiber(TCF)is a kind of special optical fiber with two parallel cores.Combining the TCF and grating,the twin-core fiber grating structure is designed,which can maintain the spectral characteristics of the twin-core fiber and grating and effectively solve the temperature cross-sensitivity problem.It is based on phase mask technology,chosing ArF excimer laser(248 nm),building a sbuild a set of new fiber grating carving system,compose a series of FBG,and test their spectral reflectance.This paper explores structural design,fabrication and characteristics of FBG,and the main contents are as follows:1.Rsoft optical simulation software was used to conduct numerical analysis and calculation,establish FBG model,obtain FBG reflection spectrum,and explore the influence of each grating parameter on FBG reflection spectrum.248 nm(ArF)excimer pulsed laser is selected as the fiber Bragg grating engraving laser.A set of FBG fabrication system was designed and built.A series of FBG were engraved with a mask(1040 nm)?Aiming at the shortcomings of optical path,the improvement scheme was proposed to optimize the optical path,and the FBG with excellent performance was obtained.Further explore the high-pressure hydrogen and high temperature annealing treatment on the influence of the grating spectrum.Finally,a temperature sensing system was built up to teste the temperature sensing characteristics of FBG.2.Rsoft optical simulation software was used to conduct numerical analysis,establish a TCF model,and analyze the bending and temperature sensing characteristics.In view of the cross-sensitivity of temperature existing in TCF bending sensor,a twin-core fiber Bragg grating structure was designed by combining TCF and FBG.The results showed that the maximum bending sensitivity was 0.05nm/cm in the range of 20 cm-60 cm,and the maximum temperature sensitivity was 0.025nm/~oC in the range of 20 cm-100 ~oC.The twin-core fiber long-period grating sensor structure was designed and the maximum bending sensitivity in the range of 20 cm-60 cm was0.205 nm/cm,and the maximum temperature sensitivity in the range of 20 ~oC-100 ~oC was 1.208nm/?.Assuming the wavelength resolution is 10 pm,the bending and temperature resolution of the twin-core fiber long period grating are 0.2 cm and 0.079 ~oC respectively,which can effectively identify the change of curvature radius and temperature.