Heterodyne detection applied to a fiber Bragg grating-based sensor using a directly modulated distributed feedback...

Area of Science:

• Optoelectronics
• Fiber Optic Sensing
• Photonics

Background:

• Fiber Bragg gratings (FBGs) are crucial for optical sensing.
• Traditional FBG sensing can face limitations in detecting weak reflections over long distances.
• Developing advanced detection methods is essential for extending FBG sensor range and sensitivity.

Purpose of the Study:

• To apply heterodyne detection to a fiber Bragg grating (FBG)-based sensor system.
• To investigate the feasibility of detecting weak FBG reflections using this technique.
• To evaluate the signal-to-noise ratio achievable with heterodyne detection for FBG sensing.

Main Methods:

• Utilized a directly modulated distributed feedback laser array as a frequency-scanning light source.
• Employed heterodyne detection to record weak reflections from the FBG.
• Configured the experiment to measure reflections from an FBG located 60 km away.

Main Results:

• Successfully recorded beat signals from weak FBG reflections.
• Achieved a high signal-to-noise ratio in the detected beat signals.
• Demonstrated clear observation of a reflection signal from an FBG with 1% reflectivity at a distance of 60 km.

Conclusions:

• Heterodyne detection is a viable technique for enhancing FBG-based sensors.
• The method allows for the detection of weak FBG reflections over extended distances (60 km).
• This approach offers a high signal-to-noise ratio, improving the performance of long-range FBG sensing systems.