ODU Clock Transmission to Reduce GMP Gap Noise
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Solution Overview
Problem
The performance of a CBR clock recovered at the tail end of an OTN network degrades due to gap noise generated in the GMP process and the accumulation of multiple gap noises, leading to weak system tracking capability.
Innovation Solution
A method where phase discrimination is performed on the transmit end clock and ODU clock to generate a PD value, which is inserted into the ODU container, ensuring no deviation during transmission, and the receive end adjusts the recovered clock based on PD values to minimize noise impact from intermediate nodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If GMP mapping/demapping is used for rate adaption during TDM mapping and encapsulation, then rate adaption is achieved, but gap noise is caused to the clock and performance degrades when multiple intermediate devices are cascaded
Solution Approach 1:
The patent extracts the clock signal from the data stream and processes it separately from the GMP mapping/demapping process. By taking out the clock recovery function and processing it independently at the tail end, the harmful gap noise generated during intermediate device processing is eliminated while maintaining rate adaption capability through the original GMP process.
Solution Approach 2:
The patent segments the clock recovery process from the data processing process. The data undergoes GMP mapping/demapping through intermediate devices while the clock signal is recovered and processed separately at the tail end, allowing independent optimization of each function and preventing noise accumulation.
2Productivity
If multiple intermediate devices are cascaded to extend network coverage, then network capacity increases, but gap noises accumulate and recovered clock performance degrades
Solution Approach 1:
The patent extracts the clock signal processing from the intermediate device chain and concentrates it at the tail end. This allows multiple intermediate devices to be cascaded for extended network coverage while the clock performance is determined only by the transmit and receive ends, preventing noise accumulation from intermediate devices.
3Reliability
If ultra-low bandwidth is used in CBR clock recovery loop to filter noise, then noise filtration is achieved, but system tracking capability becomes weak
Solution Approach 1:
The patent converts the harmful gap noise generated during GMP processing into a manageable condition by separating its source from the clock recovery path. The noise is isolated to data processing while the clock recovery uses a clean signal path, allowing the use of higher bandwidth filters that improve both noise filtration and tracking capability simultaneously.
Data Source
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AI summary
This application relates to the field of OTN network technologies, and more specifically, to a clock transmission method. The method includes: obtaining a first optical channel data unit ODU container; performing phase discrimination on an obtained first clock and a first ODU clock of a transmit end, to generate a first PD value; inserting the first PD value into an overhead of the first ODU container; and encapsulating the first ODU container into a second ODU container, and sending the second ODU container, where a rate of the second ODU container is higher than a rate of the first ODU container. The first PD value is transmitted in the first ODU container, and the first ODU container is not decapsulated in a subsequent transmission process. Therefore, in an entire transmission process, no deviation, for example, no noise, is caused to the first PD value inserted into the first ODU container. In this way, final recovery of the first clock is not affected, so that a deviation between a finally recovered clock and the first clock is greatly reduced.