Multiplexing technique using amplitude-modulated chirped fiber Bragg gratings

Area of Science:

• Optoelectronics
• Fiber Optic Sensors
• Signal Processing

Background:

• Multiplexing techniques are crucial for increasing the capacity of fiber optic sensor systems.
• Chirped Fiber Bragg Gratings (CFBG) offer wavelength-division multiplexing capabilities but often require distinct center wavelengths.
• Existing methods face challenges in achieving high-density multiplexing and accurate signal demodulation in the presence of noise.

Purpose of the Study:

• To introduce a new multiplexing technique for fiber optic sensors using amplitude-modulated CFBGs with identical center Bragg wavelengths.
• To demonstrate the effectiveness of discrete wavelet transform for signal demodulation and wavelet denoising for noise reduction.
• To validate the proposed technique through experimental strain measurements.

Main Methods:

• Fabrication of chirped fiber Bragg gratings with unique amplitude modulation patterns.
• Multiplexing of gratings with identical center Bragg wavelengths within a shared bandwidth.
• Demodulation of the multiplexed signals using discrete wavelet transform and noise reduction via wavelet denoising.

Main Results:

• Successful multiplexing of multiple gratings with identical center Bragg wavelengths.
• Strain measurements up to 1250 microepsilon achieved with absolute error and cross-talk within +/-20 microepsilon and 16 microepsilon, respectively.
• Demonstrated a high strain resolution of 4 microepsilon.

Conclusions:

• The proposed amplitude-modulated CFBG multiplexing technique offers a viable solution for high-density fiber optic sensing.
• The combination of discrete wavelet transform and wavelet denoising effectively demodulates signals and mitigates noise.
• The technique shows excellent accuracy and resolution for practical strain measurement applications.