Real-Time Measurement and Uncertainty Evaluation of Optical Path Difference in Fiber Optic Interferometer Based on...

Area of Science:

• Optical physics
• Metrology
• Interferometry

Background:

• Optical interferometers are essential for sensing and measurement.
• Real-time optical path difference (OPD) measurement and uncertainty evaluation are critical for system optimization.
• Existing methods lack comprehensive analysis of auxiliary interferometer calibration's impact on OPD measurement uncertainty.

Purpose of the Study:

• To achieve real-time OPD measurement of a main interferometer using wavelength modulation.
• To evaluate the measurement uncertainty of the main interferometer's OPD.
• To assess the impact of different auxiliary interferometer calibration methods on OPD measurement accuracy.

Main Methods:

• Utilized a homodyne quadrature laser interferometer (HQLI) as the main interferometer.
• Employed a 3x3 interferometer as the auxiliary interferometer.
• Compared auxiliary interferometer calibration using optical spectrum analyzer scanning versus ruler measurement.

Main Results:

• The auxiliary interferometer was identified as the most significant source of measurement uncertainty.
• Total uncertainty increases linearly with increasing OPD.
• High-precision calibration and a large-OPD auxiliary interferometer enhance real-time OPD measurement accuracy.

Conclusions:

• The auxiliary interferometer's calibration significantly impacts OPD measurement uncertainty.
• Optimizing auxiliary interferometer calibration is key to minimizing system noise and ensuring consistency.
• The proposed scheme enables accurate OPD measurements for applications requiring ~m level OPDs, such as vibration, hydroacoustic, and magnetic field sensing.