Distributed Optical Fibre Acoustic Source Localization
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Solution Overview
Problem
Conventional sensor systems for locating acoustic sources are limited by the number of sensors that can be deployed and their fixed spatial locations, which are laboriously and time-consuming to redeploy, and rely on unreliable signal strength for determining source position, especially in applications like hydraulic fracturing and security monitoring.
Innovation Solution
A method using a distributed optical fibre sensor system with multiple acoustic sensors that process acoustic signals to determine the position of acoustic sources by analyzing the time of arrival and phase of acoustic energy, employing an interferometer to enhance signal processing and achieve high spatial resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional acoustic arrays with limited sensors are deployed, then device complexity is reduced, but measurement precision and spatial resolution deteriorate
Solution Approach 1:
The optical fibre sensor is divided into multiple discrete sensing points along its length, with each point acting as an independent acoustic sensor. This segmentation allows the system to achieve high spatial resolution equivalent to having many discrete sensors, while actually using a single continuous fibre optic cable as the sensing medium.
Solution Approach 2:
The patent replaces conventional mechanical acoustic sensors (hydrophones, geophones) with an optical sensing system. Light pulses are transmitted through the optical fibre and acoustic vibrations modulate the optical properties, allowing acoustic detection without mechanical contact. This substitution enables higher precision measurement while reducing the complexity of deploying numerous mechanical sensors.
2Adaptability or versatility
If the spatial locations of sensors are made fixed to simplify deployment, then ease of operation is improved, but adaptability deteriorates
Solution Approach 1:
The optical fibre sensor system transitions from fixed sensor arrays to a dynamic, flexible sensing network. The fibre can be easily repositioned, reconfigured, or redeployed to different locations and geometries without requiring complex sensor-by-sensor reinstallation. The flexible nature of optical fibre allows rapid adaptation to different monitoring scenarios while maintaining simple deployment procedures.
Solution Approach 2:
The optical fibre serves multiple functions simultaneously: it acts as the acoustic sensing medium, provides the structural support for the sensor array, and enables signal transmission. This multi-functionality allows the same fibre to be deployed in various configurations (linear arrays, 2D grids, 3D volumes) and applications without requiring different sensor types or deployment methodologies.
3Measurement precision
If signal strength is used to determine source position, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The system performs preliminary calibration by measuring the time of flight of acoustic signals between known sensor pairs before actual positioning. This pre-established timing relationship creates a reference framework that simplifies subsequent position calculations. The phase difference measurements are also pre-processed to extract timing information, preparing the data for accurate source localization without requiring complex real-time computations.
Solution Approach 2:
The patent introduces time of flight and phase difference as intermediary parameters that mediate between the raw acoustic signal and the final position determination. Instead of directly using signal strength, the system measures the time it takes for acoustic energy to travel between sensors and the phase relationship between signals. These intermediary measurements provide more accurate position information while maintaining manageable signal processing complexity.
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 accurate and efficient localization of acoustic sources over large areas with high spatial resolution, overcoming the limitations of conventional systems by providing the equivalent of many thousands of point sensors and enabling reliable distance measurement independent of signal strength.
Implementation Method 1
a distributed optical fibre sensor... acoustic signals received at the plurality of acoustic sensors are processed
Implementation Method 2
employing an interferometer to enhance signal processing and achieve high spatial resolution
Data Source
Figure 1
Figure 1b
Figure 2~3
AI summary
A method and a system are provided, in which acoustic signals received by distributed acoustic sensors are processed in order to determine the position of a source or sources of the acoustic signals. The method and system are able to determine the position of several acoustic sources simultaneously, by measuring the corresponding several acoustic signals. Furthermore, the strength of the acoustic signal or signals can be determined. The location of the acoustic source may be overlaid on a map of an area being monitored, or be used to generate an alarm if perceived to correspond to a threat or an intrusion, for example in a pipeline monitoring application. Alternatively, the method and systems can be used to monitor a hydraulic fracturing process.