Frequency transfer via a two-way optical phase comparison on a multiplexed fiber network

Area of Science:

• Physics
• Optical Engineering
• Metrology

Background:

• Accurate optical frequency comparisons are crucial for advanced technologies.
• Existing methods often struggle with noise introduced by optical fibers.
• Remote comparisons are essential for distributed sensing and networking.

Purpose of the Study:

• To develop and demonstrate a two-way remote optical phase comparison technique.
• To achieve ultra-high stability in optical frequency comparisons over long fiber links.
• To passively cancel fiber noise for improved measurement accuracy.

Main Methods:

• Launching two optical frequency signals in opposite directions within a single optical fiber.
• Simultaneously measuring optical phases at both ends of the fiber link using digital electronics.
• Implementing a passive noise cancellation scheme by allowing light to travel only once in the fiber.

Main Results:

• Achieved an ultimate stability level of 10(-21) for optical frequency comparisons.
• Successfully demonstrated the technique on a 47 km metropolitan fiber link.
• Passive noise cancellation proved effective in enhancing measurement precision.

Conclusions:

• The developed two-way remote optical phase comparison technique offers significant advantages over active cancellation methods.
• This method enables highly stable optical frequency comparisons over existing fiber infrastructure.
• The technique has potential applications in metrology, telecommunications, and distributed sensing.