Low-loss reciprocal optical terminals for two-way time-frequency transfer

Area of Science:

• Optical physics and engineering
• Atmospheric optics
• Metrology and time-frequency transfer

Background:

• Accurate time-frequency transfer is crucial for scientific applications and communication networks.
• Atmospheric turbulence poses a significant challenge for free-space optical communication links.
• Existing solutions for free-space time-frequency transfer can be costly and complex.

Purpose of the Study:

• To design and evaluate a low-cost, compact free-space optical terminal.
• To enable reliable optical two-way time-frequency transfer over turbulent atmospheric links.
• To investigate the impact of atmospheric turbulence on pointing control and terminal design.

Main Methods:

• Development of a reciprocal free-space terminal with tip/tilt pointing compensation.
• Characterization of terminal insertion loss (∼1.5 dB).
• Performance evaluation across horizontal, 2-km, 4-km, and 12-km turbulent links with varying losses (15 dB, 24 dB, 50 dB).

Main Results:

• The terminal successfully demonstrated optical two-way time-frequency transfer.
• Insertion losses were minimal, indicating efficient optical signal transmission.
• Link losses varied significantly with distance and atmospheric conditions, highlighting the impact of turbulence.

Conclusions:

• The developed low-cost terminal effectively compensates for atmospheric turbulence.
• Tip/tilt pointing control is essential for maintaining link stability and enabling accurate time-frequency transfer.
• The study provides valuable insights into free-space optical terminal design for robust atmospheric communication.