Fiber Bragg grating laser sensor with direct radio-frequency readout

Area of Science:

• Photonics and Optical Sensing
• Fiber Optic Sensors
• Laser Technology

Background:

• Traditional fiber optic sensors often require separate components for interrogation, sensing, and readout, increasing complexity and cost.
• Existing thermo-mechanical fiber sensors offer good performance but can be bulky and expensive.

Purpose of the Study:

• To demonstrate a novel fiber Bragg grating (FBG)-coupled ring laser sensor.
• To integrate the interrogating source, sensing head, and readout instrument into a single fiber-optic device.
• To develop a cost-effective and compact sensing solution with performance comparable to state-of-the-art sensors.

Main Methods:

• Utilizing a fiber Bragg grating (FBG) within a bidirectional fiber ring to couple counterpropagating modes.
• Generating a splitting of resonant wavelengths proportional to FBG reflectivity.
• Monitoring the beat note frequency generated by simultaneously lasing split resonances using a frequency counter.

Main Results:

• The sensor successfully integrates all essential components into a single fiber-optic device.
• A beat note frequency is generated whose shift directly tracks changes in the FBG reflectivity spectrum.
• The sensor eliminates the need for an optical spectrometer, significantly reducing size and cost.
• Sensing performance is demonstrated to be comparable to existing state-of-the-art thermo-mechanical fiber sensors.

Conclusions:

• The demonstrated FBG-coupled ring laser sensor offers a highly integrated, cost-effective, and compact solution for fiber optic sensing.
• The frequency-based readout mechanism simplifies the sensing setup and reduces overall system expenses.
• This technology presents a promising alternative to conventional fiber optic sensing systems, particularly where size and cost are critical factors.