TWDM PON Equalization Delay Update for Accurate Ranging
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Solution Overview
Problem
In time- and wavelength-division multiplexed (TWDM) passive optical networks (PONs), the existing methods for updating equalization delays when ONUs tune between different OLT channels lead to inaccurate ranging and potential rogue ONU issues due to inconsistent equalization delays across channels, causing service interruptions and inefficiencies in channel switching.
Innovation Solution
The system updates equalization delays by collecting and distributing the necessary information before channel tuning, using revised messages like the Ranging_Time PLOAM message with upstream and downstream channel IDs, allowing ONUs to store and apply new equalization delays directly, thereby eliminating the need for re-ranging and reducing service interruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If equalization delays are not updated before channel tuning, then the system maintains simple operation, but ranging accuracy deteriorates leading to rogue ONU issues
Solution Approach 1:
The system performs preliminary equalization delay updates by distributing target equalization delays from the source OLT to the target OLT before the ONU actually tunes channels. This preliminary action ensures that when channel switching occurs, the equalization delays are already synchronized, preventing ranging accuracy issues and rogue ONU problems without requiring complex real-time adjustments during switching.
Solution Approach 2:
The source OLT acts as an intermediary that collects equalization delay information and distributes it to the target OLT before channel tuning. This intermediary mechanism ensures consistent equalization delays across OLTs, eliminating the need for each OLT to independently manage ranging parameters and reducing the complexity of distributed delay management.
2Reliability
If re-ranging is performed during channel switching, then ranging accuracy is maintained, but service interruptions increase
Solution Approach 1:
The system updates equalization delays in advance before channel switching occurs, so that when the ONU tunes to a new OLT, the target OLT already has the correct equalization delay values. This eliminates the need for re-ranging operations during switching, maintaining service continuity while preserving ranging accuracy through pre-synchronized delay parameters.
3Measurement precision
If equalization delays are updated in real-time during channel tuning, then ranging accuracy is maintained, but service interruptions increase
Solution Approach 1:
The system performs equalization delay updates in advance during a message exchange phase before the actual channel tuning occurs. The source OLT sends target equalization delay information to the target OLT, which stores it for immediate use when switching occurs. This preliminary update eliminates the need for real-time delay adjustment during channel switching, maintaining both delay consistency and service continuity.
4Speed
If channel switching is performed without pre-synchronized equalization delays, then operation speed is maintained, but ranging accuracy deteriorates
Solution Approach 1:
The system performs a preliminary message exchange phase where equalization delay information is collected and distributed before channel switching. This pre-synchronization allows the actual channel switching to proceed rapidly without compromising ranging accuracy, as the target OLT already has the correct delay values ready for immediate application.
Solution Approach 2:
The channel switching process is segmented into distinct phases: a preliminary phase for equalization delay synchronization through message exchange, and an execution phase for actual channel tuning. This segmentation allows the time-consuming delay synchronization to occur separately from the speed-critical channel switching operation, maintaining both accuracy and speed.
Data Source
AI summary
A passive optical network (PON) includes a first optical line terminal (OLT), a second OLT, and an optical network unit (ONU). The first OLT sends an equalization delay change message to the ONU, wherein the equalization delay change message includes an equalization delay, an upstream channel ID and a downstream channel ID corresponding to the equalization delay. The ONU receives the equalization delay change message. When the ONU tunes from the first OLT to the second OLT, the ONU obtains the equalization delay for upstream transmission according to the upstream channel ID and the downstream channel ID.