Optical Fiber Ranging With OLT–ONU Latency Compensation
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Solution Overview
Problem
The existing PON system struggles to accurately calculate the length of optical fibers between optical network units (ONUs) and optical line terminals (OLTs due to interference from inherent latencies and signal processing times, leading to inaccurate distance measurements.
Innovation Solution
An optical fiber ranging method that accounts for inherent latencies and signal processing times by using compensation distances for OLT and ONU latencies, calculating distances based on propagation speed and multiple ranging requests to eliminate measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the OLT calculates distance based on the interval between sending the ranging message and receiving the response message, then the distance measurement process is simple, but the measurement precision deteriorates due to response duration variations
Solution Approach 1:
The patent extracts and separately compensates for the response duration component from the total time interval. By identifying and removing the ONU processing time (response duration) from the round-trip time measurement, the system isolates the pure light propagation time, thereby eliminating the source of measurement error while maintaining the simplicity of the ranging process
Solution Approach 2:
The patent changes the measurement parameter from the raw time interval (which includes response duration) to the compensated time interval (round-trip time minus response duration). This parameter transformation converts an inaccurate measurement into an accurate one by adjusting for the known response duration characteristic of each ONU model
2Device complexity
If the OLT uses the round-trip time interval to calculate distance, then the calculation method is straightforward, but the reliability deteriorates due to latency variations
Solution Approach 1:
The patent implements a feedback mechanism where the OLT obtains the response duration parameter from the ONU (either pre-configured or reported by the ONU itself) and uses this feedback information to correct the distance calculation. This feedback loop ensures that the calculation accounts for the specific processing characteristics of each ONU, improving reliability without significantly increasing system complexity
Solution Approach 2:
The patent performs preliminary determination of the response duration parameter before the actual distance calculation takes place. By pre-obtaining and storing the response duration characteristics of each ONU model, the system prepares the correction data in advance, allowing for reliable and accurate distance calculations during normal operation without adding computational complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enhances the precision of optical fiber length measurement by compensating for latency-related errors, allowing for accurate calculation of distances and efficient topology structure determination in PON systems.
Implementation Method 1
calculates the distance between the OLT and the ONU with reference to a propagation speed of light over an optical fiber
Data Source
AI summary
An optical fiber ranging method and device are provided to accurately measure the length of an optical fiber between an optical network unit (ONU) and an optical line terminal (OLT) by using an optical signal. The optical fiber ranging method improves precision of measuring the distance between the OLT and the ONU.