High-resolution optical frequency dissemination on a telecommunications network with data traffic.

Area of Science:

• Physics
• Metrology
• Optical Communications

Background:

• High-precision frequency transfer is crucial for advanced scientific applications like distributed quantum computing and enhanced sensing.
• Existing fiber optic networks offer potential infrastructure for long-distance frequency dissemination but face challenges with noise and data interference.

Purpose of the Study:

• To demonstrate the feasibility of transferring an ultrastable laser frequency over a long-distance urban fiber link that simultaneously carries internet data.
• To investigate and mitigate the phase noise introduced by the fiber link.
• To assess the achievable frequency stability for practical dissemination.

Main Methods:

• Utilized a dense wavelength-division multiplexing (DWDM) scheme to transmit the metrological signal and internet data over separate frequency channels.
• Employed bidirectional off-the-shelf optical add-drop multiplexers for seamless integration of the metrological signal into the communication network.
• Implemented a round-trip technique with an all-fiber interferometer to measure and cancel link-induced phase noise.

Main Results:

• Achieved successful frequency transfer of an ultrastable laser over a 108-km urban fiber link.
• Demonstrated that the metrological signal can coexist with internet traffic without significant degradation.
• The compensated fiber link exhibited an Allan deviation of 10(-16) at 1 second and below 10(-19) at 10,000 seconds.

Conclusions:

• The study successfully demonstrates the simultaneous transfer of ultrastable laser frequency and internet data over a shared urban fiber optic network.
• The implemented phase noise cancellation technique significantly enhances frequency stability, making long-distance dissemination practical.
• This work establishes a foundation for disseminating precise optical clock signals between laboratories using existing communication infrastructure.