Optical Fiber Boundary Detection Using Waveform Dispersion
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Solution Overview
Problem
Existing optical fiber test methods face difficulties in detecting connection points due to increasing noise levels towards the distal end of the fiber, making it challenging to accurately determine the boundary using simple differential values or thresholds.
Innovation Solution
The method involves acquiring return light intensity over time from a light pulse emitted into an optical fiber, calculating change and randomness values along the fiber, and comparing these to determine the boundary point, using the increased dispersion caused by noise as a threshold to accurately identify the connection point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If simple differential value or threshold method is used to detect connection points, then the detection method is simple and easy to implement, but the detection accuracy deteriorates due to increasing noise levels toward the distal end
Solution Approach 1:
The patent introduces randomness value as an intermediary parameter to mediate between the simple differential value method and the noisy distal end signals. By comparing the differential value with the randomness value at each position, the method filters out noise while preserving connection point detection capability, thus maintaining simplicity while improving accuracy.
Solution Approach 2:
The patent changes the detection parameter from a fixed threshold to a dynamic threshold based on local randomness. Instead of using a constant threshold value, the method calculates the randomness value at each position and uses it as an adaptive threshold, allowing the detection criterion to adapt to the varying noise conditions along the fiber length.
2Loss of information
If light pulse measurement is performed to obtain optical power distribution, then the optical fiber transmission loss and connection loss are integrated providing comprehensive information, but noise is superimposed toward the distal end making boundary detection difficult
Solution Approach 1:
The patent applies partial action by focusing only on the relevant portion of the signal characteristics. Instead of analyzing the entire optical power distribution curve which includes integrated loss information, the method extracts and analyzes only the local differential value and randomness value at each position, filtering out the integrated loss information that contributes to noise accumulation.
Solution Approach 2:
The patent segments the optical fiber measurement into multiple small sections along the longitudinal direction. By calculating differential values and randomness values for each segment independently, the method transforms the continuous noisy signal into discrete localized measurements, making boundary detection feasible even in high-noise regions.
3Length of stationary object
If noise amount increases at the distal end portion, then the signal-to-noise ratio deteriorates, but the measurement range is extended to cover the entire fiber length
Solution Approach 1:
The patent applies dynamics by making the detection threshold dynamic rather than static. The randomness value calculated at each position serves as a dynamic threshold that adapts to the local noise conditions. This allows the measurement range to be extended to the entire fiber length while maintaining reliability, as the threshold automatically adjusts to the varying signal-to-noise ratio along the fiber.
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 approach allows for the detection of optical fiber line boundaries regardless of noise levels, effectively distinguishing between noise-induced changes and actual connection points, even in the presence of high noise at the distal end.
Implementation Method 1
emitting a light pulse to one end of an optical fiber to be tested
Implementation Method 2
receiving backscattered light generated by the light pulse
Data Source
AI summary
An object of the present invention is to provide an optical fiber test method, an optical fiber test apparatus, and a program, capable of detecting a boundary of an optical fiber line facility regardless of a change in a noise amount. A change amount (a differential value) of an OTDR waveform increases toward a distal end due to noise effects, making it difficult to determine a boundary of the optical fiber using the change amount. Therefore, in the present invention, a dispersion of the OTDR waveform, which increases toward a distal end due to noise effects, is also used to determine the boundary of the optical fiber. In other words, in the present invention, the noise amount is expressed by the dispersion, and the dispersion is compared with the change amount such as a differential value as a threshold, to determine the boundary of the optical fiber. For this reason, when noise increases, the threshold increases together with an increase in the change amount, and therefore, the boundary of the optical fiber can be determined regardless of noise.