Performance Analysis of Apodized Fiber Bragg Gratings for Sensing Applications
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ORIGINAL PAPER
Performance Analysis of Apodized Fiber Bragg Gratings for Sensing Applications Souryadipta Maiti 1 & Vivek Singh 1 Received: 10 October 2020 / Accepted: 18 November 2020 # Springer Nature B.V. 2020
Abstract Sensing performance of fiber Bragg grating in presence of various apodization functions are studied and compared. Using couple modes theory and matching the fields at various boundaries, the equation of reflectivity of fiber Bragg grating sensors are obtained. The sensors are optimized to get maximum reflectivity with narrow full width half maximum of the resonance peak. It is observed that all considered apodization functions suppress the sidelobes. The suppression of dominating sidelobe is maximum −141.29 dB for Blackman apodization function in all considered cases. The larger sensitivity 6.07 AU/RIU and 6.06 AU/RIU is obtained in Bessel apodization function and Barthann apodization function, respectively. Since, Bessel apodization function shows lower (0.1500 nm) fullwidth half maximum value in comparison to the Barthann apodization function, therefore it gives maximum detection accuracy10329 and quality parameter 40.47 AU/nm-RIU. Followed by Bessel apodization function the Gaussian apodization function also shows high detection accuracy10030 and quality parameter 38.18 AU/nm-RIU due to its lower (0.1545) fullwidth half maximum value. Here the considered Bessel apodization function is recommended for sensing applications. Keywords Apodization . Bragg grating . Detection accuracy . Quality parameter . Sensitivity
1 Introduction In last few decades Fiber Bragg Gratings (FBGs) and photonic crystal fibers have dramatically widened over the optical communication and optical sensing application [1]. Now a days, these waveguide-based sensors drawn much attention in biosensing applications [2, 3]. These waveguide-based sensors are lightweight, have small form factor, linear output, susceptible to EM waves and electrical environment, tolerant of harsh environments, remote sensing, long-term stability, miniature size, multiplexing, fatigue durability, ease and low cost of installation etc. FBGs are nothing but an optical wavelength coded filter, created either by periodic/quasi-periodic modulation of refractive index of waveguide or by periodic variation of physical dimensions of the waveguide core. This periodic aspect results multiple reflections of forward traveling wave
* Vivek Singh [email protected]; [email protected] 1
Department of Physics, Institute of Science, Banaras Hindu University, Varanasi, U.P. 221005, India
and create a relative phase of reflected signal. Under Bragg condition, all the reflected light signals combine coherently to one large reflection at a particular wavelength, which is called Bragg wavelength [4]. Only those wavelengths that satisfy the Bragg condition are strongly back reflected through the same core of the fiber. Hence, the working principle of FBGs sensors are based on the Bragg’s reflection condition and by properly choosing the lengths, period o
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