Highly compact fiber Fabry-Perot interferometer: A new instrument design.

Area of Science:

• Optics and Photonics
• Metrology and Measurement Science

Background:

• Accurate displacement measurement is crucial across various scientific and industrial fields.
• Existing interferometers often face limitations in size, environmental robustness, and alignment sensitivity.

Purpose of the Study:

• To design, construct, and characterize a novel optical-fiber-based Fabry-Perot interferometer.
• To achieve continuous, high-precision displacement measurement over a wide range.
• To develop a compact and robust sensor tolerant to misalignment and harsh environments.

Main Methods:

• Utilized a simple Fabry-Perot cavity formed by an optical fiber end and a reflecting surface.
• Employed sinusoidal wavelength modulation of an infrared laser source.
• Implemented phase measurement derived from photodetector signals at modulation frequency (f) and its harmonic (2f).
• Applied compensation algorithms to reduce inherent non-linearities.

Main Results:

• Demonstrated a compact (125 µm diameter) displacement sensor with >5° misalignment tolerance.
• Achieved displacement measurement from nanometers to tens of millimeters.
• Reduced phase errors to below 3 nm using compensation algorithms.
• Enabled absolute surface separation measurement via wavelength sweep.

Conclusions:

• The developed optical-fiber interferometer offers a unique combination of compactness, robustness, and precision.
• The sensor is suitable for continuous displacement monitoring in diverse and challenging environments.
• This technology advances capabilities in high-resolution metrology.