Advanced optimization algorithms for grating based sensors: A comparative analysis

This study explores the use of advanced optimization algorithms for determining optimum parameters for grating based sensors. Shift in wavelength in the resonance bands is always accompanied by reduction in loss of the attenuation peaks due to changing coupling coefficients in long period grating sensors. Maximization of strength of the rejection bands is considered as the objective function to enhance the range of detection for both amplitude and wavelength based demodulation schemes. Effect of grating period, length of the grating and peak induced index change, on core cladding mode resonances has been analyzed in detail. Transmission loss in resonance bands and shift in the resonance band are strong functions of the grating period, length of grating, peak induced-index change, order of the cladding mode and fiber parameters. The results of effect of optimization algorithms on the convergence and fitness values of the objective functions are reported. Transmission spectra obtained by analytical model has been verified with the experimental results. Maximum transmission loss of ≈76 dB has been achieved with optimized grating parameters. Effect of variation of the optimized parameters by 10% on the strength of rejection band has been analyzed.