Wavelet-Based Demodulation of Multimode Etched Fiber Bragg Grating Refractive Index Sensor

Area of Science:

• Photonics and Optical Sensing
• Nanotechnology and Material Science

Background:

• Etched fiber Bragg grating (EFBG) sensors are utilized for refractive index detection via evanescent fields.
• Increased sensitivity in thin fibers leads to multimode behavior and spectral enlargement, complicating sensor interrogation.

Purpose of the Study:

• To develop an advanced spectral analysis method for multimode etched fiber Bragg gratings (MMEFBGs).
• To improve refractive index sensing by analyzing spectral density, independent of peak reflectivity.

Main Methods:

• Analysis of MMEFBG spectra in the wavelet domain.
• Utilizing the integral of spectral density as a novel sensing estimator.
• Fabrication of MMEFBGs using hydrofluoric acid and testing with water/sucrose mixtures.

Main Results:

• The wavelet-domain analysis effectively quantifies spectral density, offering a new approach to MMEFBG interrogation.
• The proposed spectral density integral estimator demonstrates superior performance compared to conventional wavelength shift methods.
• Refractive index sensitivity was successfully evaluated, validating the efficacy of the developed interrogation technique.

Conclusions:

• The wavelet-based spectral density analysis provides a robust method for interrogating MMEFBGs.
• This approach effectively leverages the spectral enlargement characteristic of multimode sensors for enhanced refractive index sensing.