Timestamp Counter for SFP Transceiver SyncE Clock Chain
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Solution Overview
Problem
The introduction of Ethernet signal processing at the physical layer in Small Form-factor Pluggable (SFP) transceivers compromises the Synchronous Ethernet (SyncE) clock chain, affecting the performance of Precision Time Protocol (PTP) as defined in IEEE1588, due to long intra-node paths for timestamping ingress/egress messages.
Innovation Solution
A pluggable transceiver module with a timestamp counter that generates counter values based on external clock signals, sending these values to both the line transmitter and receiver, and associates them with timing packets, ensuring accurate timestamping close to the Line interface for improved PTP performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If Ethernet signal processing is introduced at the physical layer in SFP transceivers, then flexibility of connecting electrical or optical Ethernet is improved, but time synchronisation performance deteriorates due to long intra-node paths
Solution Approach 1:
The patent divides the SFP transceiver into functionally separate components: a line side interface (line receiver/transmitter) for optical/electrical Ethernet conversion, and a unit side interface (unit receiver/transmitter) for connecting to the host device. This segmentation allows independent optimization of each interface, enabling the line side to maintain SyncE clock chain integrity while the unit side provides flexible Ethernet connectivity through PHY processing.
Solution Approach 2:
The patent introduces an intermediary timestamp counter and associated timestamping mechanism that operates at the line side interface, close to where the optical/electrical conversion occurs. This intermediary timestamping system provides accurate time stamps for PTP messages by capturing timestamps at the point of ingress/egress, thereby compensating for the delays introduced by PHY processing and long intra-node paths.
2Ease of operation
If PHY processing is added to SFP for electrical Ethernet, then ease of operation is improved, but clock chain integrity deteriorates affecting PTP performance
Solution Approach 1:
The patent segments the signal processing functions by placing the PHY (physical layer) processing at the unit side interface, separate from the line side interface that handles optical/electrical conversion. This segmentation allows the line side to maintain a clean SyncE clock chain for PTP operations, while the PHY processing at the unit side provides ease of operation for electrical Ethernet connectivity without compromising clock chain integrity.
Solution Approach 2:
The patent introduces an intermediary timestamp counter that operates independently at the line side, close to the optical/electrical conversion point. This intermediary timestamping mechanism captures precise timestamps for PTP messages before they undergo PHY processing, thereby maintaining clock chain integrity and PTP performance while still allowing PHY processing to provide ease of operation.
3Device complexity
If timestamping is performed after long intra-node paths, then device complexity is reduced, but measurement precision of timestamps deteriorates
Solution Approach 1:
The patent performs timestamping as a preliminary action at the line side interface, close to where the optical/electrical conversion occurs and where messages ingress/egress the SFP. By capturing timestamps at this early point in the signal path, the system achieves high measurement precision for PTP messages, and this preliminary timestamping information is then used by the host device to calculate synchronization without requiring complex post-processing.
Data Source
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AI summary
A pluggable transceiver module (200) comprising a line receiver (208) connected to a unit interface transmitter (202), a line transmitter (206) connected to a unit interface receiver (204) and a timestamp counter (210) adapted to generate counter values based on clock signals received from an external source and to send the counter values to the line transmitter (206) and to the line receiver (208). The line transmitter (206) and the line receiver (208) are adapted to associate timing packets in a stream of data packets transmitted and received by the pluggable transceiver module (200) with counter values output by the timestamp counter (210).