OLT Time Synchronization Using ONU Clock Sources
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In passive optical networks, the precision of time synchronization decreases when multiple ONUs have high-precision time sources, and the OLT relies on a time source from the core network, requiring multi-level transmission over a packet network.
Innovation Solution
The OLT receives clock information from a first ONU, adjusts its local time for synchronization, and sends this information to other ONUs, eliminating the need for clock signals from the upper network and reducing multi-level packet network transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the OLT obtains ToD from a core network time source through multi-level packet network transmission, then the time synchronization can be achieved, but the precision of the ToD decreases
Solution Approach 1:
The patent extracts the time synchronization function from the core network and implements it locally within the PON network. The OLT receives clock information directly from ONUs and adjusts its local time accordingly, eliminating the need for multi-level packet network transmission from the core network and thereby preserving time precision.
Solution Approach 2:
The PON network becomes self-sufficient in time synchronization by utilizing clock information from ONUs that already possess high-precision time sources. The OLT serves itself and other ONUs by distributing this clock information locally, without requiring external core network time sources.
2Reliability
If the OLT obtains clock information from the core network, then time synchronization is maintained, but bandwidth resources of the upstream interface are consumed
Solution Approach 1:
The OLT obtains clock information from ONUs within the same PON network rather than from the core network. This self-service approach maintains time synchronization reliability while eliminating the consumption of upstream bandwidth resources that would otherwise be used to receive clock information from external sources.
Solution Approach 2:
The patent combines the time synchronization function with the existing PON network infrastructure. The clock information is exchanged through the same optical network units and transmission medium already used for data communication, thereby avoiding additional bandwidth consumption for separate synchronization channels.
3Measurement precision
If multiple ONUs have high-precision time sources, then better time synchronization is possible, but the OLT still relies on core network time sources, making the system complex
Solution Approach 1:
The patent introduces dynamic selection of time sources at the OLT. The OLT can receive clock information from multiple ONUs and dynamically select the most appropriate source based on current network conditions, thereby maintaining both high precision and system flexibility without relying on fixed core network time sources.
Solution Approach 2:
Instead of the traditional approach where the OLT receives time information from the core network and distributes it to ONUs, the patent inverts the flow by having the OLT receive clock information from ONUs and use it for synchronization. This inversion leverages the existing high-precision time sources at the ONU level.
Data Source
AI summary
A method for time synchronization on a passive optical network is disclosed, including: an optical line terminal (OLT) receives clock information sent by a first optical network unit (ONU); the OLT adjusts local time of the OLT according to the clock information, to implement clock synchronization between the OLT and the first ONU; the OLT sends the clock information to a second ONU, to implement clock synchronization between the second ONU and the OLT. The OLT in an embodiment of the present invention does not need to obtain clock signals from an upper network and the clock information does not need to be transmitted in a multi-level mode over a packet network; therefore, the precision of ToD can be greatly increased.