Optical Switching Delay Synchronization via Time-Tagged Ranging
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Solution Overview
Problem
In switching systems, accurately measuring propagation delays between transmitter and receiver is challenging due to unknown propagation delays and the need for efficient throughput, which can result in data loss if the receiver is not in the correct receiving mode when the frame arrives.
Innovation Solution
A method involving time-tagged ranging messages and trial-and-error adjustments of time delays to determine successful transmission intervals, using phase 0, 1, 2, and 3 ranging messages to measure delays between transmitter, receiver, and switch, synchronizing clocks with Precision Time Protocol, and adjusting delays based on transmission success rates and error detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If propagation delay measurements are performed using traditional methods, then the system can operate, but transmission success is not guaranteed due to unknown delays affecting receiver mode timing
Solution Approach 1:
The system performs preliminary delay measurements and receiver mode timing adjustments before actual data transmission. The transmitter sends test frames and the receiver adjusts its mode transition timing in advance, ensuring proper synchronization is established before throughput-critical operations begin.
Solution Approach 2:
The system uses feedback from test transmission results to iteratively adjust the receiver mode transition timing. By monitoring whether frames are successfully received and using this information to refine delay measurements and timing adjustments, the system converges on optimal synchronization parameters.
2Productivity
If fast acquisition receiver mode is used to improve throughput efficiency, then data transmission speed increases, but data is lost if the receiver is not in the correct receiving mode when the frame arrives
Solution Approach 1:
The receiver performs preliminary timing adjustments by testing when to transition from wait mode to fast acquisition mode. By determining the optimal transition timing in advance through controlled test transmissions, the receiver ensures it will be in the correct mode when actual data frames arrive, preventing data loss while maintaining high throughput efficiency.
3Reliability
If the connection interval is extended to ensure frame traversal, then transmission reliability improves, but system resource utilization decreases
Solution Approach 1:
The system performs delay measurements and timing synchronization in advance, allowing the switch to use precise timing information for subsequent transmissions. This preliminary characterization of propagation delays enables the system to use shorter, more efficient connection intervals while maintaining reliability, as the timing is pre-optimized based on measured characteristics.
Data Source
AI summary
A system and method for measuring propagation delays and other delays in an optical switching system. A transmitter is connected, through a circuit switch, to a receiver. To measure the propagation delay between the transmitter and the receiver, the transmitter sends one or more time-tagged ranging messages and the receiver calculates a propagation delay from the difference between the time of receipt and the time of transmission. In another embodiment, a time delay between message transmission and transition of a CDR of the receiver to a fast acquisition mode is adjusted, by trial and error, to find a range of such time delays for which transmission is successful. A time delay between the transmitter and the switch is measured by establishing or breaking the connection and determining, for various tentative time delay values, whether transmission succeeds.