Distributed Optical Fibre Sensor Infrasonic Detection
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Solution Overview
Problem
Distributed optical fibre sensors struggle to detect slow changes in the environment, such as leaks or structural deformations, which do not produce distinct acoustic signatures in the audible frequency range, limiting their ability to identify events of interest.
Innovation Solution
A distributed optical fibre sensor system that processes infrasonic signals and uses coherent Rayleigh backscatter interference to detect changes in refractive index along the fibre, enabling the detection of slow changes in temperature and strain, and employs an analyser with components like infrasonic frequency filters and phase trackers to identify events based on event models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If distributed optical fibre sensors use audible frequency range detection, then they can detect vibrations with distinct acoustic signatures, but they fail to detect slow changes in the environment such as leaks or structural deformations that do not produce audible acoustic signatures
Solution Approach 1:
The patent extends the frequency detection range from audible frequencies to include infrasonic frequencies (below 20 Hz). This parameter change in the detection bandwidth enables the sensor to capture slow environmental changes such as temperature variations, strain changes, and fluid leaks that manifest as infrasonic vibrations rather than audible acoustic signatures, thereby resolving the contradiction between detection precision for audible events and versatility for slow environmental changes
2Reliability
If distributed optical fibre sensors focus on audible acoustic signatures, then they can identify events with distinctive sound patterns, but they lose the ability to detect events that produce only infrasonic signals
Solution Approach 1:
The patent introduces infrasonic frequency analysis as an intermediary detection mechanism that captures environmental changes before they manifest as audible acoustic signatures. By processing the infrasonic frequency components of the backscattered light signal, the system preserves information about slow environmental changes such as temperature drift, strain accumulation, and fluid leakage that would otherwise be lost, thereby maintaining reliability while preventing information loss
3Measurement precision
If distributed optical fibre sensors use coherent Rayleigh backscatter interference techniques, then they can detect vibrations, but they struggle to distinguish slow environmental changes from noise in the audible frequency range
Solution Approach 1:
The patent segments the frequency spectrum into distinct bands, specifically isolating the infrasonic frequency range from the audible frequency range. By applying bandpass filtering and frequency-domain analysis to the coherent Rayleigh backscatter interference signal, the system separates slow environmental changes (infrasonic) from typical vibration events (audible), making it easier to detect and differentiate between the two types of events without confusion from noise in the audible range
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
The system effectively detects events like fluid leaks or structural deformations by analyzing infrasonic frequency changes in the coherent Rayleigh backscatter interference signal, providing additional information beyond audible acoustic signatures, and refining event location using spatial and temporal characteristics.
Implementation Method 1
detects changes in the environment of a sensing optical fibre from the properties of probe light backscattered within the sensing fibre... detects variations in refractive index, induced by a physical forcing such as vibration, in the coherent Rayleigh backscatter interference profile of light backscattered within a sensing optical fibre
Data Source
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AI summary
The disclosure relates to distributed optical fibre sensors arranged to detect coherent Rayleigh backscatter from a sensing optical fibre disposed in an environment, and to determine an infrasonic signal in the backscatter, or to determine a change in the environment within an infrasonic frequency range from the backscatter..