Optical Module Timing Circuitry for PTP Synchronization
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Solution Overview
Problem
Advanced optical modules in high-bandwidth networks introduce dynamic and unpredictable delay asymmetry, which complicates precise time synchronization between nodes, leading to inaccuracies in timing synchronization due to differences in forward and reverse path delays.
Innovation Solution
Implementing Precision Time Protocol (PTP) clock functionality within optical modules, including timing circuitry that mitigates delay asymmetry by determining residence time and communicating it via PTP messages, and utilizing reserved bits in Alignment Markers for timestamp references, enabling precise timestamping and synchronization across optical modules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If advanced optical modules with complex PMA/PMD functions and SD-FEC are used to achieve high bandwidth, then network capacity increases, but dynamic and unpredictable delay asymmetry is introduced that degrades time synchronization accuracy
Solution Approach 1:
The patent segments the time synchronization function by implementing separate timestamping mechanisms at different boundaries (ingress and egress of the optical module). This allows independent measurement of delays in each direction, enabling compensation for delay asymmetry introduced by complex optical module functions like SD-FEC and coherent modulation.
Solution Approach 2:
The patent introduces an intermediary timestamping mechanism within the optical module that acts as a mediator between the physical layer processing and the network layer synchronization protocol. This intermediary captures precise timestamps at module boundaries, allowing the system to account for delays introduced by intermediate processing functions.
2Ease of manufacture
If round trip delay measurement is used to estimate one-way delay for time synchronization, then synchronization can be achieved without additional infrastructure, but delay asymmetry between forward and reverse paths causes time errors
Solution Approach 1:
The patent implements feedback by using the timestamp information captured at module boundaries to compensate for delay asymmetry. The system measures the actual delay experienced by synchronization packets through the optical module and uses this feedback to correct time synchronization calculations, improving accuracy over simple round-trip estimation.
Solution Approach 2:
The patent performs preliminary timestamping at the ingress boundary of the optical module before signals undergo complex processing. This preliminary action captures the reference time point early in the signal path, enabling accurate calculation of processing delays and their compensation in the final synchronization computation.
Data Source
AI summary
An optical module for use in an optical system is disclosed, the optical module implementing Precision Time Protocol (PTP) clock functionality therein. The optical module includes an electrical interface with the optical system; circuitry connected to the electrical interface and configured to implement a plurality of functions of functionality; an optical interface connected to the circuitry; and timing circuitry connected to the electrical interface and one or more of the plurality of functions, wherein the timing circuitry is configured to implement the PTP clock functionality.