Study on the excursion rule of resonance waves of long period fiber gratings

In order to study the dependence of the effective index and the coupling constant on the radii and refractive index of the fiber core and cladding,the relation between the structural parameters and the change of the resonance wave of the transmission spectra was obtained by means of theoretical analysis and the numerical simulation.The results show when the radii a1,a2and refractive index of fiber core and cladding n1,n2increase,the resonance wavelengths shift towards shorter wavelengths;when the grating period Λ increases,the resonance wavelengths shift towards longer wavelengths.The conclusion can be used for reference in the design of long period fiber gratings.