Performance evaluation of a time-division multiplexed fiber Bragg grating sensor based on heterodyne detection

Area of Science:

• Optoelectronics
• Fiber optic sensing
• Spectroscopy

Background:

• Time-division multiplexing (TDM) is crucial for fiber optic sensor networks.
• Improving signal-to-noise ratio (SNR) in TDM systems enhances measurement accuracy.
• Fiber Bragg gratings (FBGs) are widely used sensing elements.

Purpose of the Study:

• To improve the signal-to-noise ratio (SNR) for interrogating multiple fiber Bragg gratings (FBGs) in a time-division multiplexed (TDM) system.
• To demonstrate a novel wavelength referencing technique for accurate FBG peak reflection wavelength determination.
• To validate the applicability of the developed method for long-distance fiber optic sensor networks.

Main Methods:

• Utilized heterodyne detection for FBG reflection spectra observation.
• Employed absorption lines of ¹²C₂H₂ as precise wavelength markers.
• Measured temperature dependence of peak wavelength for a single FBG to assess stability.

Main Results:

• Achieved significant improvement in signal-to-noise ratio (SNR) for TDM interrogation of three FBGs.
• Demonstrated accurate determination of FBG peak reflection wavelengths using acetylene absorption lines.
• Confirmed the method's effectiveness in a 20 km long sensor network.

Conclusions:

• The proposed heterodyne detection method with acetylene wavelength referencing effectively enhances SNR for TDM FBG interrogation.
• This technique is suitable for robust and accurate sensing applications over extended distances.
• The study validates a practical approach for improving the performance of long-haul fiber optic sensing systems.