Optimal parameters for fiber Bragg gratings for sensing applications: a spectral study

The spectral characteristics viz. reflectivity, bandwidth, and sidelobes’ intensity for uniform and apodized (Gaussian, hyperbolic tangent, apod1, sine, and raised sine) fiber Bragg gratings (FBGs) were studied as a function of grating length and index modulation. The optimal grating length and index modulation to obtain maximum reflectivity and minimum sidelobes were determined, as needed for sensing applications. The impact of various apodization profiles on the spectral response has also been assessed. The results indicate that out of the apodization profiles considered for the study, sine, Gaussian, and raised sine profiles offer the desired output. Article highlights The reflectivity (of main peak) and sidelobes’ intensity increase with grating length and index modulation. The bandwidth decreases with grating length and increases with index modulation. The ideal grating length and index modulation were found to be 5 mm and 0.0008 respectively to obtain maximum reflectivity and minimum intensity for sidelobes. Sine, Gaussian, and raised sine profiles are the best suitable apodization profiles among those considered.