Mode Coupling Theory Of Tilted Fiber Bragg Grating

In recent years,more and more researchers have focused on the study of fiber Bragggratings.Fiber Prague gratings have been widely used in sensors,lasers and communication systems.Although some devices based on Fiber Bragg grating have been put into use,there are many theoretical problems that have not been studied thoroughly.The basic principle of the study of the inclined fiber Bragg grating(TFBG)can help us to have a better understanding of the properties of the grating and to help the new applications of biosensing,chemical sensing,and other optical technology and physical phenomena,and the key to commercialization and extensive applications of TFBGS:Low cost,compact and high capacity manufacturability.In this paper,the exact vector solution of standard single mode fiber is given.The cladding mode of the fiber is multimode and there can be thousands of modes.We use Fimmwave to calculate the exact vector solution of the model.We can find that the cladding mode can be divided into two categories according to polarization characteristics: angular or radial dominance.There is no cross coupling between these two kinds of modes,and they correspond to the polarization state of P or S,respectively.Then we use MATLAB to calculate the coupling coefficient according to the polarization dependent coupling characteristics and simulate the spectrum of tilted fiber grating.In this paper,we mainly study the coupling of forward transmission core mode and cladding mode.A series of discrete resonance peaks.The mode coupling of tilted fiber gratings is not only the superposition of core mode and cladding mode,but also the structure of vector summation.The effects of dispersion,tilt angle,grating length,modulation depth,and in different media on the spectra are discussed.Dispersion will lead to an obvious drift of high order cladding mode,and the length and modulation depth of grating will significantly affect the depth of resonance peak,and it is basically linear.The influence of different media on the spectrum of tilted fiber grating is further discussed: the spectrum of tilted fiber grating in water will be compressed and a large number will appear near the cutoff wavelength.A gold-plated tilted fiber grating produces surface plasmon resonance in water.Finally,the theoretical model is compared with the experimental results.In different media and gold plating,the experimental results are well fitted.Through theoretical modeling,the length of the grating,the modulation depth,and the influence of the external refractive index on the spectrum are discussed.We can improve the sensitivity of the above parameters to improve the sensitivity of the inclined fiber Bragg grating.Degree.