Grating-assisted demodulation of interferometric optical sensors

Area of Science:

• Optics and Photonics
• Sensor Technology
• Signal Processing

Background:

• Accurate control of the operating point is vital for maximizing sensitivity in interferometric optical sensors.
• Manufacturing errors and environmental changes can perturb sensor performance, necessitating dynamic compensation.
• Existing demodulation methods may have bandwidth limitations or lack the speed and range for certain applications.

Purpose of the Study:

• To design and evaluate a grating-assisted operating-point tuning system for interferometric optical sensors.
• To demonstrate a demodulation subsystem capable of compensating for sensor perturbations and enhancing sensitivity.
• To explore the potential for absolute optical-path-difference measurement using this novel system.

Main Methods:

• A system utilizing a diffraction grating and feedback control was designed to function as a tunable-bandpass optical filter.
• The system was integrated as a demodulation subsystem for optical interferometer sensor systems employing broadband light sources.
• Performance was evaluated in a fiber Fabry-Perot acoustic-wave sensor system.

Main Results:

• The system achieved a 40-nm tuning range, a 400-nm/s tuning speed, and a 0.4-nm step resolution.
• Demonstrated no signal-detection bandwidth limit, high tuning speed, and a large tunable range.
• Significantly improved signal-to-noise ratio and fringe contrast in the tested acoustic-wave sensor system.

Conclusions:

• The grating-assisted operating-point tuning system is an effective demodulation subsystem for interferometric optical sensors.
• The method offers increased interference fringe contrast, sensitivity, and potential for absolute measurements.
• The system's performance is sufficient for most practical measurement scenarios, enhancing sensor reliability and accuracy.