A 500-km Cascaded White Rabbit Link for High-Performance Frequency Dissemination

Area of Science:

• Metrology and Precision Measurement
• Optical Communications and Networking
• Time and Frequency Transfer

Background:

• Accurate time and frequency dissemination is crucial for modern telecommunication networks and scientific experiments.
• Existing methods like GPS receivers have limitations in stability and accuracy over long distances and in challenging environments.
• The White Rabbit Precision Time Protocol (WR-PTP) offers a potential solution for high-precision time transfer over optical fiber.

Purpose of the Study:

• To investigate the performance of WR-PTP for time and frequency dissemination over long-distance, unidirectional optical fiber links.
• To assess the stability and accuracy of WR-PTP compared to commercial GPS receivers.
• To identify factors influencing WR-PTP performance, such as SoftPLL bandwidth and message rate.

Main Methods:

• Implementation of a 500 km, four-span cascaded WR-PTP link using modified White Rabbit equipment.
• Utilized unidirectional fiber links for compatibility with active telecommunication networks.
• Conducted comparative analysis with data from commercial Global Positioning System (GPS) receivers.

Main Results:

• Achieved short-term fractional frequency stability of 2×10^-12, improving to 2×10^-15 at one day of integration.
• Demonstrated WR-PTP performance superior to GPS receivers by over an order of magnitude in medium- and long-term stability and accuracy.
• Identified the impact of SoftPLL bandwidth, PTP message rate, and thermal fluctuations on fiber performance.

Conclusions:

• WR-PTP is a viable technology for high-accuracy time and frequency dissemination over extended optical fiber networks.
• The WR-PTP system demonstrates superior medium- and long-term stability and accuracy compared to GPS.
• Further optimization of WR-PTP parameters and understanding environmental effects can enhance performance.