Hydrophone Mixed Fluid Cavity for Acoustic Sensitivity
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Solution Overview
Problem
Existing fiber optic acoustic sensors face challenges in simultaneously achieving high sensitivity for detecting small acoustic pressure variations and maintaining sufficient immersion resistance for underwater applications, with existing solutions either sacrificing sensitivity or immersion resistance.
Innovation Solution
The use of a mixed fluid comprising a liquid-based fluid and microballoons within the sensor's cavity, where the proportion of microballoons is calculated to achieve a target compressibility, optimizing both sensitivity and immersion resistance without altering the sensor's general structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a special enclosure (amplifying sheath or resonant cavity) is used to amplify mechanical stress on the optical fiber, then sensitivity to pressure variations is improved, but device complexity increases and immersion resistance is compromised
Solution Approach 1:
The patent changes the physical parameters of the fluid medium by introducing microbubbles into the liquid-filled cavity. This modifies the fluid's compressibility and acoustic impedance, enabling the cavity to naturally amplify acoustic pressure on the optical fiber without requiring complex enclosing structures. The parameter change in fluid composition directly improves sensitivity while maintaining structural simplicity.
Solution Approach 2:
The patent utilizes a fluid medium (liquid with microbubbles) to transmit and amplify acoustic pressure variations to the optical fiber. By controlling the fluid's compressibility through microbubble concentration, the system achieves mechanical amplification of acoustic signals without complex mechanical enclosures, resolving the contradiction between sensitivity and device complexity.
2Measurement precision
If the sensor is designed for high sensitivity to pressure variations, then measurement precision is improved, but maximum operating immersion depth is reduced
Solution Approach 1:
The patent modifies the fluid's compressibility parameter by adjusting microbubble concentration in the liquid medium. This enables the sensor to maintain high sensitivity to pressure variations while withstanding greater external pressures at depth. The optimized fluid parameters allow the sensor to function reliably at deeper immersion depths without sacrificing measurement precision.
3Reliability
If a liquid-based fluid is used to maintain good immersion resistance, then reliability is improved, but sensitivity to acoustic pressure variations is reduced
Solution Approach 1:
The patent creates a composite fluid medium by dispersing microbubbles within a liquid carrier. This composite structure combines the benefits of liquid (good immersion resistance and incompressibility at high pressure) with gas bubbles (compressibility and acoustic sensitivity). The resulting fluid maintains reliability at depth while significantly improving sensitivity to acoustic pressure variations.
Solution Approach 2:
The patent uses a pneumatic-hydraulic composite system where gas microbubbles are suspended in a liquid medium. The microbubbles provide the necessary compressibility for acoustic sensitivity, while the liquid continuous phase maintains immersion resistance. This hybrid fluid system resolves the contradiction between reliability and measurement precision.
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 controlled optimization of sensitivity and immersion resistance, enabling the sensor to function effectively in underwater environments while maintaining a compact design, with improved sensitivity and resistance compared to conventional methods.
Implementation Method 1
A Bragg grating is a reflector comprising alternating layers of different refractive indices, which causes a periodic variation in the effective refractive index of the optical fiber. Optical acoustic sensors using Bragg gratings are used to measure the acoustic pressure that corresponds to a stress applied to the sensor, which induces a change in wavelength.
Implementation Method 2
A fiber optic acoustic sensor comprises at least one optical fiber whose optical characteristics are sensitive to the acoustic pressure to be measured. When light is injected into the optical fiber, a light signal whose characteristics depend on the acoustic pressure is generated by the hydrophone.
Implementation Method 3
The cavity is filled with a mixed fluid comprising a liquid-based fluid and a chosen proportion of microballoons. The proportion of microballoons in the mixed fluid is calculated to achieve a target compressibility of the mixed fluid, optimizing both sensitivity and immersion resistance.
Implementation Method 4
The proportion of microballoons in the mixed fluid is calculated to achieve a target compressibility, optimizing both sensitivity and immersion resistance without altering the sensor's general structure.
Data Source
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AI summary
The invention proposes an acoustic sensor device (1) with an optical fibre, comprising a casing (10) which delimits a cavity (3) and an optical fibre sensor (2), the optical fibre sensor comprising an optical fibre (12), the optical fibre extending through the casing between two points. Advantageously, the cavity (3) comprises a mixed fluid which comprises a liquid-based fluid and microballoons, the microballoons comprising gas bubbles.