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Stabilized free space optical frequency transfer using digitally enhanced heterodyne interferometry.
Optics Letters
|July 14, 2023
Summary
This study demonstrates a new method for stable free-space optical frequency transfer, overcoming signal degradation from reflections. The technique uses pseudo-random sequences to enhance precision measurement in turbulent environments.
Area of Science:
- Optics
- Metrology
- Optical Communications
Background:
- Free-space continuous-wave laser interferometry is crucial for precision measurements like velocimetry and vibrometry.
- Prompt reflections from transceiver optics often degrade system performance, especially with weak returning signals.
Purpose of the Study:
- To demonstrate phase-stabilized free-space continuous-wave optical frequency transfer.
- To overcome performance degradation caused by prompt reflections in interferometric systems.
Main Methods:
- Exploiting auto-correlation properties of pseudo-random binary sequences (PRBS).
- Implementing a filtering technique to distinguish desired signals from prompt reflections.
- Utilizing a 750 m turbulent free-space channel for testing.
Main Results:
- Achieved a best fractional frequency stability of 8 × 10-20 at a 512 s integration time.
- Demonstrated significantly improved stability and robustness in optical frequency transfer.
- Obtained cycle-slip-free periods up to 162 minutes.
Conclusions:
- The developed system effectively filters prompt reflections, enhancing optical frequency transfer.
- PRBS auto-correlation offers a robust solution for precision measurement in challenging free-space conditions.
- The method significantly improves the reliability of optical frequency transfer over turbulent channels.
