Ethernet-OTN Clock Synchronization via Asynchronous Mapping
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Solution Overview
Problem
Current Optical Transport Network (OTN) standards for Ethernet data traffic lack synchronization between Ethernet and OTN timing, requiring additional equipment and complex synchronization circuits, which increases costs and complexity.
Innovation Solution
A transceiver system with clock recovery circuits, synchronizers, and asynchronous mappers that recover and multiply clocks by integer ratios to synchronize Ethernet and OTN signals, enabling transparent timing changes at boundary nodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If GFP-F mapping is used to terminate Ethernet packets, then Ethernet data traffic can be transported over OTN, but synchronization between Ethernet timing and OTN timing is lost
Solution Approach 1:
The patent introduces an intermediary mechanism (asynchronous mapping with rate adaptation) between Ethernet packets and OTN frames to preserve timing information. The system uses a buffer and rate adapter as intermediaries that allow asynchronous operation while maintaining timing relationships through metadata and control signals.
Solution Approach 2:
The patent adds a temporal dimension to the mapping process by introducing time-stamping and rate adaptation mechanisms. Instead of simple spatial mapping, the system tracks timing across different time bases using additional control dimensions (timing metadata, rate indication fields) to maintain synchronization awareness.
2Reliability
If extra equipment is added to provide stratum timing at egress, then timing synchronization is achieved, but equipment cost and operating cost increase
Solution Approach 1:
The system enables self-service timing where the OTN network itself provides timing references to Ethernet clients through the mapped frames. The timing information is embedded within the data stream through the asynchronous mapping mechanism, eliminating the need for separate external timing equipment.
Solution Approach 2:
The patent makes the OTN transport system multi-functional by enabling it to simultaneously transport data and provide timing synchronization services. The same mapping infrastructure that handles data transport also delivers timing information, consolidating multiple functions into a single system.
3Reliability
If external stratum synchronized timing is added, then timing synchronization is provided, but stringent timing wander requirements must be met
Solution Approach 1:
The patent implements prior cushioning through buffer mechanisms that absorb timing variations and wander before they propagate through the system. The asynchronous mapping buffer acts as a cushion that isolates timing disturbances, preventing them from affecting the synchronized timing relationship.
4Manufacturing precision
If stratum synchronization circuits are added to address wander requirements, then timing wander is controlled, but system complexity and cost increase
Solution Approach 1:
The patent replaces complex mechanical/electrical stratum synchronization circuits with a software-based or logic-based asynchronous mapping system. The timing control is achieved through digital signal processing and protocol manipulation rather than dedicated hardware synchronization circuits.
Data Source
AI summary
A method and system for transparent timing of an Ethernet signal over an optical transport network are disclosed. In one embodiment, a transceiver includes a first clock recovery circuit, a first synchronizer and an asynchronous mapper. The first clock recovery circuit recovers a first clock from a first signal received from an Ethernet network. The first synchronizer multiplies the first clock by a ratio M/N to produce a second clock to time a second signal transmitted over the optical transport network. M and N are integers. The asynchronous mapper maps frames of the first signal to produce frames of the second signal.