Low-Coherence Homodyne Interferometer for Sub-Megahertz Fiber Optic Sensor Readout

Area of Science:

• Optoelectronics and Sensor Technology
• Interferometry
• Fiber Optics

Background:

• Interferometric fiber optic sensors offer high sensitivity but often face challenges in demodulation stability and bandwidth.
• Active homodyne demodulation and low-coherence interferometry are established techniques with distinct advantages for signal processing.

Purpose of the Study:

• To develop an advanced readout method for interferometric fiber optic sensors.
• To enhance sensor performance by integrating active homodyne demodulation with low-coherence interferometry.
• To achieve high sensitivity, stability, and a wide frequency band in sensor measurements.

Main Methods:

• A tandem low-coherence interferometer was employed to modulate the reference interferometer independently of the sensing element.
• Active homodyne demodulation was utilized for signal processing.
• A fiber Michelson interferometer served as the sensing element for acoustic signal detection.

Main Results:

• The proposed method demonstrated high sensitivity, achieving up to 0.1 nm (RMS).
• The system maintained high stability across measurements.
• A wide frequency band capability was achieved, demonstrated within a 5 kHz range.
• Successful detection of acoustic signals was confirmed.

Conclusions:

• The integration of active homodyne demodulation and low-coherence interferometry provides a robust method for fiber optic sensor readouts.
• The technique significantly enhances sensitivity, stability, and operational bandwidth.
• This approach is effective for precise acoustic signal detection using fiber optic sensors.