Fiber Bragg grating sensor interrogation system based on an optoelectronic oscillator loop.

Area of Science:

• Photonics and Optical Sensing
• Microwave Photonics
• Fiber Optic Sensors

Background:

• Fiber Bragg Grating (FBG) sensors are widely used for various physical parameter measurements.
• Traditional FBG interrogation techniques can be complex and costly.
• A need exists for sensitive and cost-effective FBG interrogation methods.

Purpose of the Study:

• To propose and demonstrate a new interrogation technique for FBG sensors.
• To convert FBG wavelength variations into frequency shifts using an optoelectronic oscillator (OEO).
• To evaluate the performance of this technique for axial strain sensing.

Main Methods:

• An optoelectronic oscillator (OEO) loop incorporating the FBG sensor as the optical source was designed.
• The OEO loop included an electro-optic modulator (EOM), dispersive element, electric filter, and photodiode (PD).
• The FBG's wavelength change was converted into an oscillating frequency shift due to the loop's wavelength-dependent time delay.

Main Results:

• A proof-of-concept experiment demonstrated axial strain sensing using the proposed FBG-OEO technique.
• A linear relationship was observed between the OEO's microwave signal frequency and applied axial strain.
• A sensitivity of approximately 58 Hz/με was achieved using dispersion compensation fiber (DCF).

Conclusions:

• The proposed OEO-based FBG interrogation technique effectively converts wavelength shifts into frequency variations.
• This method offers a sensitive and potentially cost-effective approach for FBG sensor interrogation.
• The technique is applicable to various optical sensors that rely on wavelength detection.