Fiber Bragg grating sensing system for temperature measurements based on optically injected DFB-LD with an OEO loop

Area of Science:

• Photonics and Sensing Technology
• Optical Engineering
• Metrology

Background:

• Fiber Bragg Grating (FBG) sensors are widely used for various measurements.
• Existing FBG sensing systems face limitations in sensitivity and tunability for temperature monitoring.
• Distributed feedback laser diodes (DFB-LDs) offer potential for enhanced optical sensing.

Purpose of the Study:

• To propose and demonstrate a novel FBG sensing system for high and tunable sensitivity temperature measurements.
• To integrate an optically injected DFB-LD with an optoelectronic oscillating (OEO) loop for improved signal quality.
• To convert temperature variations into frequency variations of a microwave signal for accurate detection.

Main Methods:

• Utilizing an FBG sensor as an edge filter to modulate the optical power of an injected beam.
• Operating the optically injected DFB-LD in a Period-one (P1) oscillating state.
• Implementing an OEO loop to enhance the signal quality of the generated P1 microwave signal.
• Correlating the frequency of the P1 microwave signal with applied temperature changes.

Main Results:

• The proposed FBG sensing system achieved tunable sensitivity ranging from 0.44322 GHz/°C to 1.25952 GHz/°C.
• High measurement accuracy of 0.0629°C was demonstrated through stability and repeatability tests.
• The system successfully converted temperature variations into frequency shifts of the P1 microwave signal.

Conclusions:

• The novel FBG sensing system offers high sensitivity and tunable performance for temperature measurements.
• The integration of DFB-LD and OEO loop enhances signal quality and measurement accuracy.
• The system demonstrates excellent linearity, flexible sensing generality, and low error, making it suitable for advanced temperature monitoring applications.