Angled Fiber End Optical Sensor for High-Pressure Measurement
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Solution Overview
Problem
Existing optical sensors for contactless pressure measurements are limited by sensitivity and reliability in harsh industrial environments with high temperatures and high pressure conditions, and require complex designs and materials that are not compatible with such conditions.
Innovation Solution
An intensity-modulated optical sensor with an optimized design and angled cut fiber end surface to reduce Fresnel back reflections, allowing for improved Signal to Noise Ratio (SNR) and sensitivity, and compatibility with high temperatures, using a single mode or multimode fiber to detect pressure changes without antireflective coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical sensors are used in harsh industrial environments, then pressure measurement capability is maintained, but reliability and sensitivity deteriorate due to high temperatures and high pressure conditions
Solution Approach 1:
The patent replaces conventional electronic pressure sensing elements with an optical sensing system that uses a deformable reflective diaphragm and optical fiber to detect pressure changes. This substitution eliminates the need for electronic components that are sensitive to high temperatures, thereby maintaining reliability in harsh thermal environments while preserving pressure measurement capability
2Measurement precision
If interferometric optical sensors are used to achieve high resolution pressure measurement, then measurement precision is improved, but device complexity and cost increase due to coherent LASER sources and complicated optical design
Solution Approach 1:
The patent employs inexpensive LED light sources and standard optical fibers instead of expensive coherent LASER sources and complex interferometric setups. While LEDs have shorter coherence length, the system achieves sufficient measurement precision for industrial applications by using intensity modulation with a deformable reflective diaphragm, thereby reducing device complexity and cost while maintaining adequate measurement resolution
Solution Approach 2:
The patent changes the measurement approach from interferometric phase detection to intensity modulation detection. By monitoring intensity changes of reflected light from a deformable diaphragm rather than phase changes, the system achieves practical measurement precision with simpler optical components and LED sources, thereby reducing device complexity while maintaining sufficient precision for industrial pressure measurement
3Reliability
If electronic pressure sensors are used in areas with high electromagnetic interference, then pressure measurement is performed, but signal degradation occurs due to EMI and RF interference
Solution Approach 1:
The patent replaces electronic sensing elements with an all-optical sensing system that uses optical fibers to transmit measurement data. Since optical fibers are electrically passive and immune to electromagnetic interference, the system maintains signal stability in high EMI environments while continuing to perform accurate pressure measurement
4Measurement precision
If optical sensors with antireflective coatings are used to reduce Fresnel back reflections, then Signal to Noise Ratio is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent introduces asymmetry by angling the cut of the optical fiber end surface instead of using a conventional flat perpendicular cut. This angled configuration reduces Fresnel back reflections into the fiber core by directing reflected light away from the core, thereby improving Signal to Noise Ratio. The angled cut is a simple geometric modification that does not require complex antireflective coatings, maintaining ease of manufacture while achieving the desired optical performance
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 sensor effectively detects small deformations of the pressure sensing diaphragm with increased reliability and robustness, enabling accurate high-pressure measurements in harsh industrial environments, such as automotive combustion chambers, without the need for direct mechanical contact or hazardous materials.
Implementation Method 1
fiber optic is used to drive incoming optical beam in front of the pressure sensing reflective diaphragm and to collect the light beam reflected by the diaphragm itself
Implementation Method 2
The end surface of the fiber is angled cut to reduce the Fresnel back reflections
Implementation Method 3
the pressure transducer is based on a deformable pressure sensing diaphragm whose deformation with pressure may be changed modifying its thickness
Data Source
Figure 1
Figure 2a~2c
Figure 3
AI summary
An optical sensor for pressure measurements is described which comprises a sensor head (8) including: - a diaphragm (9) having a first surface (91) in contact with a fluid of which the pressure has to be measured and a second surface (92) opposite to the first surface, - a body with a tubular cavity (200), - means (92, 10) arranged inside the tubular cavity, associated with the second surface of the diaphragm and movable longitudinally inside said tubular cavity in response to the deformation of the diaphragm, said means including a reflective surface (92, 102), - an end part (12) of waveguide means (4) arranged inside the tubular cavity and having the end surface (11) faced to and not in contact with the reflective surface (92, 102) of said means, said waveguide means being connected to a light source (1) and a receiver (5) respectively to send to said means the light beam (50) deriving from the light source and to collect at the receiver the light beam (60) reflected from the reflective surface of said means, the intensity of the collect light beam being dependent on the distance (D) between the end surface of the end part of waveguide means and the reflective surface. The end surface (11) of the end part (12) of waveguide means is tilted with respect to a plane orthogonal (B) to the optic axis (A) of a first angle (α) having a value such that the incident angle (θa) of the light beam deriving from the light source is less than the critical angle (θc-air) between the waveguide means and the air and greater than the critical angle (θc) of the waveguide means, and the reflective surface (102, 92) of said means is tilted with respect said plane (B) orthogonal to the optic axis (A) of a second angle (β) equal to the escaping angle of the light beam from said end surface (11) of the end part (12) of waveguide means.