Sensitivity Analysis of HF Etched Uniformly Thinned <i>α</i>-Power Refractive Index Profile Fiber Bragg Grating Sensor
Sanjeev Kumar Raghuwanshi, Yadvendra Singh, Purnendu Shekhar Pandey, Ritesh Kumar
Abstract
An α-power refractive index profile circular core fibre Bragg grating (FBG) sensor has been numerically and experimentally analysed for the first time. In the experiment, 40 % concentrated hydrofluoric acid (HF) has been used to fabricate an etched fibre Bragg grating (e-FBG) sensor with variable cladding thickness. The proposed study can also be demonstrate the marginal tuning capability of Bragg wavelength shift by deeply etched cladd process. The target of this paper is to analyse the α-power refractive index profile e-FBG sensor. For this purpose transfer matrix method (TMM) has been devised to analyse the complicated double-clad waveguide structure while grating is taken along the length of fibre core. In this paper, three samples have been fabricated and analysed with various etched cladding thicknesses viz. 6 μm, 8 μm, and 10 μm, which give significant change in the refractive index sensitivity. Experimental results of sensitivity analysis have been matched closely with the numerical one. The estimated maximum sensitivity of the developed α-power e-FBG sensor has been found ≈ 35 nm/RIU. Also, this value is equivalent to the minimum change in the refractive index of ≤ 10-5. It has been found that Bragg wavelength can be tune marginally as a result of reducing the cladding diameter. It has been noticed that the tuning range can be substantially improved by deep etching process along with α-power refractive index profile FBG and found to be 4.5 × 10-3 RIU at optimum cladding diameter.