Sensing performance of apodized fiber Bragg gratings having linearly tapered profile

The sensing performance of a linearly tapered and apodized fiber Bragg grating is estimated and optimized. Coupled mode theory in association with the transfer matrix method is utilized to develop the reflectance formula of the proposed sensor. The reflectance spectra of linearly tapered fiber Bragg gratings are plotted for various apodization profiles. The sensitivity, detection accuracy, and quality parameter of proposed sensor are compared with standard fiber Bragg grating and linearly tapered fiber Bragg gratings-based sensors. It is found that the tapering in the waveguide along with apodization further improves the sensing performance of the sensor. Although the maximum sensitivity 489 nm/RIU is obtained in Hamming apodization and maximum left side lobe - 152 dB is obtained in Barthann apodization function, these apodizations show poor detection accuracy and quality parameters due to their larger value of full width at half maxima of sensing signal. The Bessel apodization function shows maximum detection accuracy (1366) and quality parameter (420/RIU) in our all-considered linearly tapered apodized structures. Followed by Bessel apodized sensor, the Blackman apodized sensor also shows higher detection accuracy (1340) and quality parameter (412/RIU). Therefore, these two apodization functions are recommended for biosensing applications in such a tapered structure.