Analysis Of Fiber Grating Sensor Characteristics And Scientific Computing

With the maturity and improvement of the production technology of fiber grating, fiber grating gradually is more and more widely in the light field such as optical information processing, optical communications, optical fiber sensing and so on. Not only has strict requirements on the peak and bandwidth of fiber grating reflective spectrum, and need to control the shape of reflection spectrum, even need to develop the grating that with characteristic reflection spectrum shape.The guidance of fiber grating sensing properties is absolutely necessary for the production and development of the specific structure of the fiber grating. Therefore, it is very important to master the characteristics of fiber grating. At present, we have obtain the influence of various structural parameters on the reflection spectrum of fiber grating,by means of simulating the spectral characteristics and drawing out the reflection spectrum of the fiber grating. Such variation of sensing characteristics of the fiber grating can be mastered better. the theoretical foundation and the reference of parameter choice can be provided to the production and design of fiber grating,in order to guide the design of fiber grating products that meets the performance requirements.From the developed the first fiber grating, has also developed non-uniform period fiber grating with different purposes and structures. These researches on the sensing properties of fiber grating all can base on the sensing properties of fiber bragg grating. The reflection spectrum of the non-uniform periodic grating had happened significant changes comparing with the reflection spectrum of the fiber bragg grating. the bandwidth of reflection spectrum is significantly increased, and the reflection rate is significantly decreased. So, improving the accuracy of the reflectance and the strictly of reflection spectrum is very important to application of the grating.However, in the process calculation of the coupled-mode equations, ignore the influence that the weak coupling between the two core mode on reflection spectrum.So,it’s need to pose a grating coupling model with weak coupling term.According to the coupled mode theory, to analyze the physical meaning of the coupling between the two reverse core mode that along the grating axially based on the transmission ways of the light waves in optical fiber grating structure. Considered the impact of the weak coupling terms in the coupled mode equations to the reflection spectrum. We retain the weak coupling term, compute scientifically, and derive the grating coupling model with weak coupling terms. Then with the grating coupling model with weak coupling terms and the grating coupling model without weak coupling terms respectively research sensing properties of fiber Bragg grating,chirp grating and blazed grating.The innovations in this paper are as follows:(1)According to the transmission characteristics of light waves in the fiber grating structure, we consider that the weak coupling impact the reflection spectrum of fiber grating. We retain the weak coupling term in the coupled mode equations.Improve the existing grating coupling model without weak coupling terms,and change into the grating coupling model with weak coupling terms.(2)According to the bandwidth formula without weak coupling terms,wavelength width between adjacent peaks and adjacent zero has been derived. And we pose the bandwidth formula with weak coupling terms. In addition, we compare the bandwidth formula with weak coupling terms with the bandwidth formula without weak coupling terms.(3) With the grating coupling model with weak coupling terms and the grating coupling model without weak coupling terms respectively simulate fiber Bragg grating,chirp grating and blazed grating.The sensing characteristics of fiber grating is analyzed specifically in different grating length,different grating period, and different refractive index modulation, different chirp coefficient, different tilt angles, group delay, KL and so on. We compare reflection of two models,and obtain the relationship between the various parameters and the reflection spectrum of the grating.