Investigation of Grating Parameters Impact on Spectral Characteristics of LPFG using Two-Layer Fiber Geometry

The study on spectral characteristics of long period fiber grating (LPFG) explores its usefulness in many applications. This scenario insists the researchers to calculate the impact of LPFG's parameters on its characteristics. The paper presents the effect of grating length and grating period on the spectral characteristics of LPFG. Their impact is calculated in terms of variation in position of resonant wavelength and attenuation band depth. For this, the transmission profiles of LP₀₃ and LP₀₅ cladding modes are kept under observation here. The spectral profiles are calculated using analytical expressions obtained through coupled mode theory. The two layer fiber geometrical model is implemented on SMF28 optical fiber parameters to evaluate propagation constants of fiber's core region's and cladding region's modes. The results show linear increase in attenuation depth of spectrum with increase in grating length. On the other hand, with the rise in periodicity the shift in resonant wavelength is towards longer wavelengths.