Optical Fiber Clock Synchronization Asymmetry Compensation
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Solution Overview
Problem
Current clock synchronization techniques in optical networks, such as Precision Time Protocol (PTP) IEEE 1588v2, introduce errors due to asymmetrical optical fiber paths, which are not accurately accounted for, especially in advanced networks like 5G where precise timing is critical.
Innovation Solution
The method involves calculating propagation delays at different wavelengths to estimate the length of optical fibers on both forward and reverse paths, allowing for adjustment of clock synchronization to account for asymmetry without additional hardware, using the PTP protocol in conjunction with physical characteristics of the optical fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If PTP protocol assumes symmetrical optical fibers for clock synchronization, then calculation is simplified, but synchronization accuracy deteriorates due to propagation delay errors in asymmetrical paths
Solution Approach 1:
The patent changes the parameter used for delay calculation from a fixed half-round-trip assumption to a dynamically determined one-way delay value. By measuring the actual one-way propagation delay through timestamp comparison between master and slave nodes, the system adapts to asymmetrical fiber conditions while maintaining synchronization accuracy without excessive complexity
Solution Approach 2:
The patent replaces the mechanical assumption of symmetrical paths with an optical measurement-based approach. By using optical timestamp measurements and calculating actual propagation delays based on measured values rather than theoretical assumptions, the system achieves accurate synchronization in asymmetrical conditions
2Measurement precision
If additional hardware is deployed to measure optical fiber length accurately, then synchronization precision improves, but device complexity and cost increase
Solution Approach 1:
The patent enables the existing PTP infrastructure to measure fiber length and propagation delay using only the timestamping capabilities already present in standard PTP implementations. The master and slave nodes use their existing clocks and timestamp mechanisms to self-determine the one-way delay without requiring external measurement devices
Solution Approach 2:
The patent makes the existing PTP timestamping mechanism serve dual purposes: both clock synchronization and propagation delay measurement. The same hardware components that perform time-stamping for synchronization also provide the data needed to calculate fiber length, eliminating the need for dedicated measurement hardware
Data Source
AI summary
A method of measuring lengths of optical fibers on forward and return paths is provided in order to synchronize clocks of optical nodes connected by asymmetrical optical fiber paths. The method includes calculating, by a first optical network device, a first propagation delay of a first optical signal transmitted at a first wavelength on a first optical fiber to the first optical network device from a second optical network device and a second propagation delay of a second optical signal transmitted at a second wavelength on the first optical fiber to the first optical network device from the second optical network device. The second wavelength is different from the first wavelength. The method further includes determining, by the first optical network device, a first length of the first optical fiber based on the first propagation delay and the second propagation delay.