Coherent Optical Line Testing for Long-Range Fault Localization

Solution Overview

Problem

Existing optical fiber line testing methods, such as simple optical time domain reflectometry (OTDR), struggle with limited measurement distance, low signal-to-noise ratio (SNR), and inability to detect multiple abnormal points, especially in long-distance optical fiber lines with significant loss or reflection, and are inaccurate in overhead and underground facilities due to manholes and utility poles.

Innovation Solution

A coherent OTDR system performs coherent detection to measure long-range loss distribution and vibration distribution by time-averaging backscattered light waveforms, correlating loss points with vibration points using a coherent light measurement device to identify abnormal facilities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If simple optical time domain reflectometer (OTDR) direct detection is used, then device complexity is reduced, but measurement distance is limited and signal-to-noise ratio is low

Engineering Contradiction:

Improvedevice complexityVSAvoidsignal-to-noise ratio

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent changes the detection parameter from simple intensity detection to coherent detection, utilizing phase information of backscattered light. This parameter change enables significant improvement in signal-to-noise ratio and extends measurement distance while maintaining practical device complexity through standardized coherent detection components.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces simple direct detection with coherent detection system that uses interference between reference light and backscattered light. This substitution enables extraction of phase information and achieves high signal-to-noise ratio measurements over long distances without requiring complex mechanical scanning systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Device complexity

If simple optical time domain reflectometer (OTDR) direct detection is used, then device complexity is reduced, but measurement distance is limited

Engineering Contradiction:

Improvedevice complexityVSAvoidmeasurement distance

Core Design Contradiction:

Device complexityVSLength of stationary object

Solution Approach 1:

The patent changes the detection parameter from simple intensity detection to coherent detection, utilizing phase information of backscattered light. This parameter change enables significant improvement in signal-to-noise ratio and extends measurement distance while maintaining practical device complexity through standardized coherent detection components.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If simple optical time domain reflectometer (OTDR) direct detection is used, then device complexity is reduced, but ability to detect multiple abnormal points is lost

Engineering Contradiction:

Improvedevice complexityVSAvoidability to detect multiple abnormal points

Core Design Contradiction:

Device complexityVSLoss of information

Solution Approach 1:

The patent changes the detection parameter from simple intensity detection to coherent detection, utilizing phase information of backscattered light. This parameter change enables significant improvement in signal-to-noise ratio and extends measurement distance while maintaining practical device complexity through standardized coherent detection components.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies vibration feedback by mechanically stimulating the optical fiber at abnormal points and detecting the resulting vibration through coherent detection. This feedback mechanism enables identification of multiple abnormal points along the fiber by detecting localized vibration responses that correspond to faults such as bends, connections, or breaks.

Inventive Principle:

Principle #23Feedback

4Ease of operation

If vibration sensing is used to identify facility position, then ease of operation is improved, but measurement precision deteriorates when large loss or reflection occurs

Engineering Contradiction:

Improveease of operationVSAvoidmeasurement precision

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent merges loss distribution measurement and vibration distribution measurement into a single integrated system. By combining coherent detection of backscattered light with vibration sensing, the system achieves both functions simultaneously, allowing facility identification through vibration while maintaining accurate loss measurement even in the presence of large losses or reflections.

Inventive Principle:

Principle #5Merging (Combining)

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

Enables long-distance optical fiber line testing and accurate detection of multiple abnormal facilities, including manholes and utility poles, with improved sensitivity and dynamic range, allowing simultaneous identification of multiple failure positions.

Implementation Method 1

a coherent detection device of the present disclosure is a coherent OTDR for performing coherent detection

Methodology Applied

Scientific EffectCoherent detection: Homodyne Detection

Implementation Method 2

measuring a distribution of loss points by time-averaging a plurality of backscattered light waveforms obtained by a plurality of light pulses

Methodology Applied

Scientific EffectBackscattering: Scattering

Implementation Method 3

applying vibration to facility disposed on a path of the optical line, detecting a vibration point of the optical line

Methodology Applied

Scientific EffectVibration: Vibration

Data Source

PatentUS12529594B2Coherent optical measuring device for facility line test

Publication Date: 2026.01.20 NT T INC

AI summary

The present disclosure is an optical line test system that detects a distribution of loss points of an optical line in a longitudinal direction, using a coherent light measurement device, applies vibration to facility disposed on a path of the optical line, detects a vibration point of the optical line in a longitudinal direction upon applying the vibration, using the coherent light measurement device, and identifies the loss point based on correspondence between the detected loss point and vibration point.