OLT Broadcast Ranging Difference for Fast ONU Protection Switching
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Solution Overview
Problem
In the context of Passive Optical Network (PON) systems, especially in trunk optical fiber protection mode, the existing method for updating equalization delay signals in ONUs is inefficient, leading to prolonged service disruption during protection switching, as it requires individual one-to-one communication, exceeding the 50 ms requirement for service switching.
Innovation Solution
The method involves distributing a ranging difference (RTDΔ) between primary and standby channels to all ONUs via a broadcast message, allowing each ONU to quickly update its equalization delay signal, thereby simplifying message transmission and reducing the time required for service restoration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the OLT transmits equalization delay signals to each ONU through individual Ranging_time messages, then the ranging results are accurate, but the message quantity is large and the switching time exceeds 50 ms
Solution Approach 1:
The patent combines multiple individual Ranging_time messages into a single broadcast message that carries ranging difference information. Instead of transmitting separate equalization delay signals to each ONU individually, the OLT transmits one consolidated message containing the ranging difference (RTDΔ) that all ONUs can use to calculate their respective equalization delay signals locally, thereby reducing message quantity and transmission time while maintaining accuracy
Solution Approach 2:
The patent performs preliminary calculation of equalization delay signals at the ONU side using the received ranging difference information, rather than waiting for the OLT to calculate and transmit each individual signal. This preliminary action at the receiving end enables faster local computation and reduces the overall switching time
2Reliability
If the OLT transmits Ranging_time messages three times to ensure reliability, then the transmission reliability is improved, but the total transmission time increases significantly
Solution Approach 1:
The patent merges the content of multiple Ranging_time messages into a single broadcast message carrying ranging difference information. This consolidation maintains the essential reliability information while reducing the total number of transmission cycles from three separate messages to one consolidated message, thereby significantly reducing transmission time while preserving reliability
3Quantity of substance
If the system supports 128 ONUs with individual message transmission, then all ONUs can be served, but the total message transmission time reaches 48 ms
Solution Approach 1:
The patent applies merging by consolidating 128 individual Ranging_time messages into a single broadcast message that carries ranging difference information applicable to all ONUs. This approach maintains the capability to serve all 128 ONUs while reducing the message transmission time from 48 ms (128 messages × 125 μs each) to a single message transmission cycle
Solution Approach 2:
The patent segments the equalization delay signal transmission into two parts: (1) a common ranging difference information transmitted via broadcast message to all ONUs, and (2) local calculation of individual equalization delay signals at each ONU side. This segmentation enables parallel processing at multiple ONUs simultaneously, reducing total transmission time
Data Source
AI summary
The disclosure provides a method for quickly updating ranging results of optical network units by an optical line terminal. The method comprises the following steps: an Optical Line Terminal (OLT) distributes an acquired ranging difference to all the Optical Network Units (ONUs); and the current ONU implements quick updating of the ranging result of the current ONU itself according to the acquired ranging difference. The disclosure also provides a system for quickly updating ranging results of ONUs by an OLT, wherein a distributing unit in the OLT is used for distributing an acquired ranging difference to all the ONUs; an updating unit in the ONU is used for implementing quick updating of ranging result of the current ONU itself according to the acquired ranging difference. the method and system of the disclosure can save the quantity of messages, enable quick switching in protection status, thus implementing protection switching efficiently.