Single- and Double-Comb Tilted Fibre Bragg Grating Refractive Index Demodulation Methods with Fourier Transform...

Area of Science:

• Photonics and Optical Sensing
• Materials Science
• Signal Processing

Background:

• Accurate refractive index (RI) measurement is crucial in various scientific and industrial applications.
• Traditional fiber optic sensors often face limitations in resolution and sensitivity.
• Development of new periodic structures and demodulation algorithms is key for advanced RI sensing.

Purpose of the Study:

• To analyze the performance of a proposed double-comb Tilted fibre Bragg grating (DCTFBG) structure for refractive index measurement.
• To compare the DCTFBG sensor's capabilities against a single classical fiber Bragg grating structure.
• To introduce and evaluate novel data pre-processing and quantitative analysis algorithms for spectral data.

Main Methods:

• Utilized a DCTFBG structure, analyzing its spectral response to changes in refractive index.
• Employed Fourier Transform for pre-processing and filtering optical spectra in the frequency domain.
• Applied Hilbert transform for envelope detection and developed algorithms based on spectrum contour length and feature shifts for quantitative analysis.

Main Results:

• Demonstrated that increasing the number of modes in the DCTFBG significantly alters the Fourier spectrum.
• Successfully implemented Fourier Transform as an effective filtering method for spectral data.
• Achieved a high measurement resolution of 2 × 10^-5 refractive index unit (RIU) using the developed demodulation algorithms.

Conclusions:

• The DCTFBG structure offers a promising platform for enhanced refractive index sensing.
• The proposed Fourier Transform filtering and novel quantitative analysis algorithms significantly improve measurement accuracy and resolution.
• The developed fiber optic sensing methodology provides a robust solution for precise refractive index determination.