Implementation of a Length Gauge Based on Optical Frequency Domain Reflectometry (OFDR)

Area of Science:

• Optics
• Metrology
• Photonics

Background:

• Optical Frequency Domain Reflectometry (OFDR) is established for fiber optics but underutilized for free-space distance measurement.
• Measuring absolute distances in free space presents challenges due to complex optical paths and chromatic dispersion.

Purpose of the Study:

• To adapt OFDR for accurate free-space distance measurements.
• To address challenges of optical line composition and chromatic dispersion.
• To develop a calibration method for high-accuracy reflectometry.

Main Methods:

• Developed a mathematical framework to eliminate chromatic dispersion effects using signal transformation and an equivalent phase.
• Implemented an experimental setup with an OFDR system, collimator, and movable corner reflector.
• Employed interferometric fringe-counting for calibration.

Main Results:

• A dispersion compensation method was developed and tested, preventing peak broadening and maintaining width at tens of microns.
• Calibration determined a frequency-to-distance coefficient, yielding measurement accuracy up to 2 μm.
• Demonstrated successful adaptation of OFDR for precise measurements in free space.

Conclusions:

• OFDR can be precisely adapted for distributed distance measurements in free space.
• The developed methods significantly expand OFDR's application scope to complex environments.
• This research paves the way for high-accuracy metrology in diverse settings.