Optical Fiber Transmission Loss Abnormality Detection
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Solution Overview
Problem
Existing abnormality detection systems in facilities handling combustibles, explosives, or hazardous materials struggle to detect corrosion and wear in pipes and tanks at an early stage, leading to potential serious accidents, as they rely on intensity distribution of backscattered light which is not sensitive enough to detect minor changes and can be complicated by temperature gradients.
Innovation Solution
An abnormality detection system using optical fibers with a backscattered light detector and data processor that calculates transmission loss by acquiring intensity distributions from both ends of the optical fiber and applying a normalization function, suppressing noise and temperature gradient influences to detect abnormalities caused by external forces such as stress or bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If intensity distribution of backscattered light is used for abnormality detection, then the system can detect temperature changes, but it cannot detect minor abnormalities early due to insufficient sensitivity and temperature gradient interference
Solution Approach 1:
The patent introduces transmission loss as an intermediary parameter to detect abnormalities. Instead of directly measuring temperature or backscattered light intensity, the system measures how much light is lost as it travels through the optical fiber. This intermediary measurement is insensitive to temperature gradients but sensitive to external forces like stress and bending, thereby resolving the contradiction between detection sensitivity and reliability under temperature variations
Solution Approach 2:
The patent changes the measurement parameter from backscattered light intensity to transmission loss. By measuring the attenuation of light signal along the fiber length rather than the intensity of scattered light, the system achieves a parameter that is unaffected by temperature gradients but still responsive to mechanical abnormalities, thus improving both sensitivity and reliability
2Temperature
If distributed temperature sensor is used to monitor pipe and tank conditions, then temperature can be measured, but early-stage corrosion and wear cannot be detected
Solution Approach 1:
The patent makes the optical fiber serve multiple functions: it acts as both a temperature sensor (through backscattered light measurement) and a strain/stress sensor (through transmission loss measurement). By measuring transmission loss, the same optical fiber infrastructure can detect mechanical abnormalities like corrosion and wear that cause fiber bending or stress, without requiring separate sensing systems
Solution Approach 2:
The patent replaces direct mechanical measurement of pipe integrity with an optical measurement approach. Instead of using mechanical sensors that would physically contact the pipe, the system uses optical fiber transmission loss to indirectly detect mechanical stress and bending caused by corrosion or wear, achieving non-intrusive structural health monitoring
3Duration of action of stationary object
If optical fiber is installed around pipes and tanks for monitoring, then continuous surveillance is possible, but the system cannot distinguish between temperature-related changes and stress-induced changes
Solution Approach 1:
The patent segments the measurement information into two independent components: temperature information (from backscattered light intensity) and mechanical stress information (from transmission loss). By separating these measurements, the system can independently analyze each type of change and determine its source without interference from the other parameter
Solution Approach 2:
The patent measures transmission loss in addition to temperature, using the extra measurement to disambiguate between temperature and stress effects. While temperature measurement alone provides continuous monitoring, adding transmission loss measurement provides the additional information needed to distinguish between different causes of optical fiber response
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 system achieves higher sensitivity in detecting abnormalities, allowing for early-stage detection of issues in facilities like chemical plants and power stations, preventing potential accidents by accurately distinguishing between temperature-related and stress-induced changes in transmission loss.
Implementation Method 1
making light enter the optical fiber
Implementation Method 2
an optical fiber installed around a pipe or tank
Implementation Method 3
Raman scattered light generated inside the optical fibers is detected by the distributed temperature sensor
Data Source
AI summary
An abnormality detection system includes an optical fiber, a backscattered light detector, and a data processor. The backscattered light detector is connected to one end side and the other end side of the optical fiber, and configured to acquire a first intensity distribution of backscattered light by making light incident on the optical fiber from the one end side and to acquire a second intensity distribution of backscattered light by making light incident on the optical fiber from the other end side. The data processor calculates transmission loss at each position in the longitudinal direction of the optical fiber by using the first and second intensity distributions and a normalization function, and determines whether or not there is an abnormality based on the result of the calculation.