Fiber Optic Sensor for Shock Wave Pressure Measurement
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Solution Overview
Problem
Current technologies lack effective methods for measuring shock wave pressure in opaque solid media due to the high pressures and electromagnetic interference generated by shock waves, which limits understanding of shock wave propagation and material characteristics.
Innovation Solution
A fiber optic pressure sensor using a fiber Fabry-Perot sensor with gold coating mirrors separated by a polymer spacer, embedded in solid media, which forms an optical resonator that measures changes in cavity length caused by shock waves, and a Michelson interferometer-based sensor that measures phase shifts, providing high bandwidth and immunity to electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a pressure sensor is made sufficiently rigid to withstand the shock wave pressure, then the sensor can survive the high pressure environment, but the sensor size increases which reduces the response time and increases measurement error
Solution Approach 1:
The patent replaces traditional mechanical pressure sensors with a fiber optic Fabry-Perot interferometer that uses optical interference patterns to measure pressure changes. This substitution allows the sensor to withstand high pressures (up to 10^10 Pa) while maintaining a small size and fast response time, as the optical measurement system is not mechanically constrained by the same pressure-load relationships as conventional mechanical sensors.
2Speed
If a pressure sensor is made sufficiently small to provide fast response time, then the response time improves, but the sensor cannot withstand the high pressure generated by shock waves
Solution Approach 1:
The patent employs a fiber optic-based Fabry-Perot interferometer that replaces conventional mechanical pressure sensors. This optical measurement system enables the sensor to be both small (providing fast response time) and strong (withstanding pressures up to 10^10 Pa), as the optical interference mechanism is independent of the mechanical stress that would limit conventional sensor size.
3Measurement precision
If electronic sensors are used to measure shock waves, then the measurement capability is provided, but electromagnetic interference from the shock wave events interferes with the sensor readings
Solution Approach 1:
The patent replaces electronic sensors with a fiber optic Fabry-Perot interferometer that measures pressure through optical interference patterns. This optical measurement system is inherently immune to electromagnetic interference from shock wave events, as light propagation is not affected by electromagnetic fields, thereby eliminating the interference problem that plagues electronic sensing in high-energy shock wave environments.
4Measurement precision
If optical imaging techniques are used to image the shock front in transparent media, then shock wave speed and peak pressure can be determined, but the technique cannot be applied to opaque media
Solution Approach 1:
The patent uses a fiber optic Fabry-Perot interferometer as an intermediary measurement device that can function in both transparent and opaque media. The fiber optic sensor acts as a mediator that directly contacts the shock wave source, allowing optical measurement of pressure and velocity without requiring the medium to be transparent, thus extending measurement capability to previously inaccessible opaque materials.
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
Enables precise measurement of shock wave pressure and velocity in opaque solid media, providing fundamental understanding of shock wave propagation and material characterization under extreme conditions, with high sensitivity and directional capability.
Implementation Method 1
The fiber Fabry-Perot sensor consists of two gold coating mirrors separated by a thick polymer spacer, formed on the tip of a single mode optical fiber. The device forms an optical resonator, where the wavelength of the resonances depends on the cavity length.
Implementation Method 2
The shock wave modulating the length of the cavity, which causes a change in the reflected intensity of the laser that is measured by a photodiode receiver.
Implementation Method 3
Another embodiment is based on a reflecting fiber end incorporated into a Michelson interferometer.
Implementation Method 4
The fiber Fabry-Perot sensor consists of two gold coating mirrors separated by a thick polymer spacer
Data Source
AI summary
A fiber optic pressure and mass velocity sensor for measuring a shock wave pressure in a solid media includes an optical fiber having a means for measuring a change in an optical path length (OPL) of the fiber when positioned in the solid media caused by the shock wave altering the physical length of the fiber and the refractive index of the fiber. The means for measuring the change in the OPL is coupled at one end to a laser and at its second end to a means for detecting the change in OPL. The sensor has a high operating bandwidth (>>10 MHz), is sufficiently rigid to withstand the force of the shock wave, has a sensitivity that can also be tailored for the application, and is immune to electromagnetic interference. Measurement can be made on materials under extreme strain conditions, and the sensor can also provide characterization of protective materials such as bullet/blast proof materials.