| As a special structure of passive components,tilted fiber grating(TFBG)has the potential and advantages of light weight,small size,anti-electromagnetic interference,reusable and so on and it has wide application and broad prospect in the field of optic fiber communication and sensing.In this paper,OptiGrating optical simulation software and Matlab are used to simulate the spectrum of TFBG with different structural parameters,cascaded TFBG and TFBG in different surrounding refractive index media.The main contents are as follows:Firstly,the development course and research status of TFBG are introduced and the basic structure of TFBG is analyzed.The expressions of TFBG core mode,cladding mode and radiation mode reflectivity,Bragg resonant wavelength and cladding mode resonant wavelength and stripe visibility are derived.Secondly,the influence of different structural parameters on the spectral characteristics of TFBG is analyzed,including the influence of tilt angle,core and cladding parameters,grating period,length and refractive index modulation depth on the transmission spectrum.And the mutual compensation between different structural parameters is summarized.Finally,the cascaded TFBG structure is studied(including two cascades of the same structural grating,cascade between different structural gratings,multi-level cascade,etc).The spectral characteristics of different cascade structures were analyzed.Appling single TFBG and cascaded TFBG structure to the refractive index sensing detection.Results show that the change of the small refractive index makes the high-order cladding mode near the wavelength of 1.542?m particularly sensitive to the surrounding refractive index and in a certain range of high sensitivity,up to 10-5order of magnitude.This feature can be widely used in high precision refractive index sensing area.Compared with the performance of cascaded TFBG,it is found that cascade TFBG can improve the detection accuracy of refractive index by a factor of two. |
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