Optical Switch Module Synchronization via Round Trip Time Difference
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In optical access networks without optical switching devices, determining the connection start time for upstream optical switching elements is challenging due to the lack of medium information for obtaining delay times, which affects synchronization and packet transmission efficiency.
Innovation Solution
A synchronizing method that involves a center device transmitting downstream control packets with specific timing and identification information to remote devices, which set their clocks and transmit upstream control packets, allowing the center device to determine round trip times and calculate connection start times by subtracting delay times from the sum of transmission start times and differences in round trip times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an optical switching device is introduced into the optical access network, then packet transmission efficiency and synchronization are improved, but the complexity of determining connection start time increases due to lack of medium information
Solution Approach 1:
The patent applies preliminary action by having the OLT perform ranging measurements and calculate round trip times before the optical switching device needs to operate. The OLT determines RTTa (round trip time to remote device) and RTTs (round trip time to optical switching device) in advance, then provides the difference Tz to the optical switching device. This allows the optical switching device to calculate connection start time without needing to independently measure or determine medium delays, thus improving packet transmission efficiency while avoiding the complexity of real-time delay measurement.
2Measurement precision
If the center device calculates round trip time for each remote device, then synchronization accuracy is improved, but the communication overhead and processing time increase
Solution Approach 1:
The patent applies universality by making the OLT perform multiple functions: it acts as both the ranging master for individual remote devices and as the central coordinator for the optical switching device. The OLT calculates round trip times for multiple remote devices (RTTa1, RTTa2, etc.) and also calculates RTTs to the optical switching device, then provides the difference Tz to the optical switching device. This centralized approach achieves high synchronization accuracy for all devices while avoiding redundant processing at each remote device, thus reducing overall communication overhead and processing time.
Data Source
AI summary
To provide synchronizing methods, optical switch modules, center devices, remote devices, optical access systems, optical access networks, programs, and recording media in the optical access network which can give the connection start time of the upstream optical switching element of the optical switch module. To the optical switch module, ranging functions are provided and the center device OLU carries out ranging of the optical switch module OSM as is the case of ranging of the remote device ONU. The center device OLU transmits the difference between roundtrip time of the remote device ONU and roundtrip time of optical switch module OSM, which is the result of these rangings, to the optical switch module OSM, and the optical switch module OSM can obtain the contact start time of the upstream optical switching element by calculating the contact start time using the difference.