The Ground Beidou fiber synchronization technology is mainly used to achieve high-precision time and frequency transmission over long-distance optical fiber links, providing high-precision time and frequency signals to each site along the entire optical fiber link. The application fields of Ground Beidou fiber synchronization technology include the following aspects:
National ground-based timing network – Optical fiber timing equipment transmits UTC time information through the optical fiber network to all parts of the country, forming a unified national ground-based optical fiber timing network. It can serve as a backup for the current satellite system. However, the time and frequency accuracy obtained through the ground is about a hundred times higher than that of satellite timing, and it is highly secure and reliable. At the same time, it can prevent electromagnetic interference.
Operator-specific networks – Currently, there are two methods for timing mobile base stations of operators. The first method uses GNSS satellite timing, which is limited by the vulnerability of wireless satellite signals. When wireless satellites are interfered with, deceived, or have equipment failures, it is impossible to achieve synchronization between base stations. The second method uses ground-based PTP or White Rabbit timing. Due to the fact that PTP or White Rabbit technology relies on manual measurement and compensation for asynchronous delays, it is not feasible in engineering implementation. Moreover, factors such as an increase in PTP device hops and temperature changes will also affect the accuracy of PTP timing. If Ground Beidou fiber synchronization technology is adopted, picosecond-level time reference output can be obtained at the end timing equipment, effectively ensuring the timing accuracy of each base station.
Power grid – With the development of the power grid, the smart grid has put forward higher requirements for time accuracy. Particularly in Traveling wave distance measurement devices, synchronous phasor measurement devices, merging units, lightning locating systems, power angle measurement systems, and power grid pre-decision analysis systems, the demand for time accuracy reaches the nanosecond level. Through the Ground Beidou fiber synchronization solution, the absolute time accuracy (compared with UTC) of each substation can be better than 500ps, thereby achieving absolute time synchronization between substations and meeting the requirements of time synchronization for global control and data analysis of the smart grid. At the same time, the time signal transmitted in the closed optical fiber is less susceptible to electromagnetic interference and deception signals, with high reliability and strong stability.
Military network – The military needs to build a timing and frequency synchronization network that is not easily interfered with and is stable and reliable. High-precision time and frequency synchronization plays a decisive role in areas such as command, control, communication and intelligence, navigation, technical reconnaissance, electronic warfare, missile guidance, and identification of friendly and enemy systems. It also has important applications in radar speed measurement and high-precision positioning. Ground Beidou fiber synchronization solution can help the military reduce its excessive reliance on GNSS satellite timing and achieve a space-ground mutual backup PNT system of GNSS satellite + ground-based timing.
The following is a comparison of the advantages and disadvantages of several mainstream fiber synchronization technologies currently available:
| Feature | PTP | White Rabbit | Ground Beidou fiber synchronization |
| Accuracy | sub-microsecond to nanosecond | Sub-nanosecond | Less than 500ps |
| Error cumulative effect | Each PTP device introduces an error of 30ns to 500ns | Each hop white rabbit device introduces an error of 1ns to 5ns | Each fiber optic timing device introduces an error of 1ps to 2ps |
| Asynchronous delay | The asynchronous delay problem caused by the asymmetry of the round-trip path cannot be resolved | The asynchronous delay problem caused by the asymmetry of the round-trip link cannot be solved by algorithms. Instead, manual calibration is adopted, which has poor engineering practicality. | The asynchronous delay problem caused by the asymmetry of the round-trip link is solved by an algorithm, without the need for manual calibration. |
| Cost | Low (dedicated network card, switch) | High (dedicated hardware, fiber link) | High (dedicated hardware, fiber link) |
| Applications | Telecommunications, finance, industrial automation, radio and television | Telecommunications, particle physics, radio astronomy, synchronized phasor measurement | Telecommunications, particle physics, radio astronomy, synchronized phasor measurement |
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Email: liyan@groundbeidou.com
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