Multi-Point Fiber Bragg Grating Pressure Sensor
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Solution Overview
Problem
Fibre Bragg gratings have limited sensitivity to hydrostatic pressure, making them less effective for medical pressure measurement applications, and existing amplification methods increase sensor size, compromising their intrinsic benefits.
Innovation Solution
Etched multi-point fibre Bragg grating sensors with multiple sensing locations along a single optical fibre, sealed in a probe-type housing with optional fluid or gas-filled airspaces, and mechanical amplification features like spacers and diaphragms to enhance pressure sensitivity while maintaining a small diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical amplification schemes such as polymer coatings, pressure spacers and diaphragms are used to increase pressure sensitivity, then pressure sensitivity is improved, but sensor size increases to millimeter order
Solution Approach 1:
The optical fibre is segmented into multiple sections, each containing a fibre Bragg grating. By distributing multiple sensing points along the fibre length, the system achieves enhanced pressure sensitivity through cumulative strain effects while maintaining a compact overall sensor structure that avoids millimeter-scale dimensions.
Solution Approach 2:
The fibre Bragg gratings are nested within the optical fibre core, and multiple gratings are positioned along the fibre length. This nested configuration allows multiple sensing elements to be contained within a single fibre diameter, achieving amplified pressure sensitivity without increasing the external sensor dimensions to millimeter scale.
2Adaptability or versatility
If multiple fibre Bragg gratings are positioned along the optical fibre, then spatially distributed pressure measurements are enabled, but device complexity increases
Solution Approach 1:
A single optical fibre with multiple fibre Bragg gratings serves multiple functions: it acts as both the structural element and the sensing element, and enables spatially distributed pressure measurements at multiple locations simultaneously. This multi-functionality reduces the need for separate sensing components, thereby managing device complexity while achieving versatile measurement capabilities.
Solution Approach 2:
Multiple sensing functions are merged into a single optical fibre by positioning multiple fibre Bragg gratings along its length. This consolidation allows spatially distributed pressure measurements to be achieved without requiring multiple separate sensors, thereby reducing overall device complexity while maintaining adaptability.
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 solution significantly increases pressure sensitivity while maintaining a small, non-invasive sensor size, suitable for medical applications, and allows for simultaneous measurement of pressure and temperature changes.
Implementation Method 1
A fibre Bragg grating is contained within the core of a short segment of optical fibre that reflects particular wavelength of light and transmits all others. The Bragg wavelength is defined by Eq. 1: λB=2neffΛ where Λ is the grating period, neff is the effective refractive index of the grating in the core of the fibre and λB is the Bragg wavelength or the reflected wavelength.
Implementation Method 2
The fundamental principle behind the operation of a fibre Bragg grating is Fresnel reflection. Light traveling between media of different refractive indices may both reflect and refract at the interface.
Implementation Method 3
Any changes in refractive index, as a result of strain within the fibre due to change in temperature, pressure and the like, will cause proportional shifts in the reflected spectra.
Implementation Method 4
A fibre Bragg grating is contained within the core of a short segment of optical fibre that reflects particular wavelength of light and transmits all others.
Data Source
AI summary
A sensing device for detecting a physical parameter exemplified by pressures, strains, temperatures, indices of refraction, and combinations thereof. The sensing device comprises a probe having a housing for sealably mounting therein an optical fiber. The optical fiber is provided at its distal end with at least two spaced apart fiber Bragg gratings. The proximal end of the probe is engagable with a holder, and is in communication with fiber Bragg grating interrogation systems. Spacers and seals may be provided about the optical fiber between the fiber Bragg gratings. An orifice may be provided and sealed with a resilient membrane to provide a contained airspace around each fiber Bragg grating. The contained airspace may be optionally filled with a fluid or a gas.