Self-Mixing Interferometer for Acoustic Measurements through Vibrometric Calibration

Area of Science:

• Acoustics
• Optical Engineering
• Metrology

Background:

• Self-Mixing Interferometers (SMI) are self-aligned optical devices.
• SMIs have been utilized for acoustic wave sensing via the acousto-optic effect.

Purpose of the Study:

• To adapt and validate the use of an SMI for measuring Sound Pressure Level (SPL) within acoustic waveguides.
• To establish a calibration method for SMI sensors as acoustic pressure sensors.

Main Methods:

• In situ calibration of the SMI as a vibrometer.
• Estimation of optical feedback parameters (C and α) by solving nonlinear SMI behavior equations.
• Validation using simulated SMI signals and comparison with a reference microphone.

Main Results:

• Accurate estimation of SMI optical feedback parameters in the strong feedback regime (C≥4.6).
• SPL measurements using the calibrated SMI showed a maximal deviation of 2.2 dB compared to a reference microphone.
• Successful SPL measurement across a broad range of plane wave amplitudes (20–860 Pa) and frequencies (614–17,900 Hz).

Conclusions:

• The Self-Mixing Interferometer can be effectively calibrated and utilized as a precise acoustic pressure sensor.
• The method provides reliable SPL measurements in acoustic waveguides, demonstrating its practical applicability.
• The study validates the SMI's potential for advanced acoustic sensing applications.