OTDR Event Model Fitting for Reproducible Fiber Loss Analysis
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Solution Overview
Problem
Existing methods for detecting events in optical fibers using OTDR waveforms suffer from low reproducibility of event start point and event loss value, especially when signal-to-noise ratio is poor or event intervals are short.
Innovation Solution
Perform nonlinear fitting of an event model function to the OTDR waveform using a trust region method, utilizing an event model function defined by specific mathematical expressions to calculate event positions, levels, and losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If least-square approximation straight line is used to calculate event loss, then calculation is simple, but reproducibility of event loss value is low when events are adjacent
Solution Approach 1:
The patent changes the mathematical model from linear least-square approximation to nonlinear fitting using an event model function. This transforms the calculation approach while maintaining computational feasibility, achieving both simplicity and high reproducibility of event loss values even when events are adjacent.
2Device complexity
If change point detection method is used to calculate event position, then detection process is simple, but reproducibility of start point position is low when SN ratio is poor
Solution Approach 1:
The patent transforms the detection approach from simple change point detection to nonlinear fitting using an event model function. This parameter change in the mathematical model enables high reproducibility of start point positions even under poor SN conditions, while keeping the overall process manageable.
3Measurement precision
If nonlinear fitting of event model function is performed, then event detection reproducibility is high, but calculation complexity increases
Solution Approach 1:
The patent replaces traditional mechanical/change-point-based detection methods with a mathematical modeling approach using nonlinear fitting. This substitution achieves high reproducibility while managing calculation complexity through efficient numerical optimization techniques.
Data Source
AI summary
An object of the present disclosure is to provide a loss analysis device and a loss analysis method of detecting an event with high reproducibility when an SN ratio is small or when an event interval is short. According to the present disclosure, a loss analysis device includes an OTDR waveform acquisition unit that acquires an OTDR waveform of a measurement target optical fiber, and a calculation unit that performs nonlinear fitting of an event model function to the OTDR waveform and calculates a position of a start point of each event included in the OTDR waveform, a level at the start point of each event, a loss of each event, and a return loss of each event, the event model function using the position, the level, the loss, and the return loss as parameters.