Large range wavelength demodulation for ultra-short fiber Bragg gratings based on an arrayed waveguide grating and a...

Area of Science:

• Optical Sensing
• Photonics and Waveguide Devices

Background:

• Traditional methods for ultra-short fiber Bragg grating (US-FBG) sensors often rely on output power ratios, limiting demodulation range.
• Existing arrayed waveguide grating (AWG) based demodulation techniques face limitations in their demodulation range.

Purpose of the Study:

• To propose and demonstrate a novel wavelength demodulation method for US-FBG sensors.
• To overcome the demodulation range limitations of conventional AWG-based methods.
• To achieve high-precision, wide-range, and cost-effective demodulation of US-FBG sensors.

Main Methods:

• Utilizing an arrayed waveguide grating (AWG) to sample the US-FBG spectrum.
• Constructing underdetermined matrix equations using prior transmission response information and detected output power.
• Solving the matrix equations with a convex optimization algorithm to reconstruct the US-FBG spectrum.
• Demodulating the US-FBG by tracking the peak of the reconstructed spectrum.

Main Results:

• Successful spectral reconstruction of the US-FBG.
• Achieved a wavelength demodulation accuracy better than 4 pm.
• Demonstrated effectiveness using only five consecutive AWG channels for spectral sampling.
• Axial strain applied to the US-FBG sensor resulted in measurable peak wavelength shifts.

Conclusions:

• The proposed spectral reconstruction method enables accurate wavelength demodulation for US-FBG sensors.
• This technique expands the applicability of FBG sensors and overcomes previous range limitations.
• The method offers potential for high-precision, wide-range, flexible, and cost-effective optical sensing solutions.