Interferometric Fiber Optic Sensor Residual Cavity Design
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Solution Overview
Problem
Existing interferometric fiber optic sensors are difficult to manufacture in large quantities, have repeatable parameters, and are cumbersome to use with small samples, requiring high precision and complex mathematical models, which limits their applicability in mass production and repeatable testing.
Innovation Solution
An interferometric fiber optic sensor with a light source, detector, and optical path featuring a measuring element with a resonant cavity housed within a capillary, allowing for a residual cavity that minimizes measurement impact and simplifies manufacturing, enabling linear and easily interpretable measurements, and facilitating the detection of various substances like acetone, refrigerants, and proteins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high precision manufacturing is used for interferometric fiber optic sensors, then measurement precision is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The sensor is divided into modular components: a fiber optic probe with a resonant cavity, a capillary housing, and a measurement chamber. This segmentation allows each component to be manufactured separately with standard precision, then assembled, reducing overall manufacturing complexity while maintaining measurement precision through the controlled residual cavity design.
Solution Approach 2:
A capillary is introduced as an intermediary element between the fiber optic probe and the measurement environment. The capillary houses the probe and creates a controlled residual cavity that acts as an optical intermediary, simplifying the optical path and reducing the precision requirements for direct component interfaces.
2Measurement precision
If complex mathematical models are used for analysis, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
The complex mathematical analysis is extracted and replaced by a simplified physical model based on the controlled residual cavity. The design takes out the need for complex computational models by creating a structure where the optical path difference can be directly related to physical dimensions, enabling simple linear relationships for data interpretation.
Solution Approach 2:
The design changes the optical path parameters by introducing a controlled residual cavity with known dimensions. This parameter change transforms the measurement model from requiring complex mathematical analysis to using simple linear relationships, where the optical path difference is directly proportional to the physical displacement in the residual cavity.
3Measurement precision
If probes are designed for high precision measurement, then measurement precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The probe is segmented into standardized components that can be manufactured using conventional techniques: a fiber optic tip, a capillary tube, and a mounting structure. This segmentation allows each part to be manufactured independently with standard precision, then assembled, greatly improving ease of manufacture while maintaining measurement precision through the controlled residual cavity.
Solution Approach 2:
The probe design accepts that the fiber optic probe itself may be a disposable or replaceable component. By designing the probe as a simple assembly of inexpensive components (fiber tip, capillary, mount), it becomes economically viable to replace probes rather than repair them, simplifying manufacturing and inventory management while maintaining measurement precision.
4Measurement precision
If residual cavity is minimized, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The residual cavity is extracted and isolated as a distinct, controlled element within the capillary structure. Rather than trying to eliminate it entirely, the design takes out the residual cavity and gives it a defined, manageable size that simplifies the optical model while maintaining sufficient measurement precision for the application.
Solution Approach 2:
The design changes the parameter of the residual cavity from an uncontrolled variable to a controlled design parameter. By specifying a particular size range for the residual cavity (minimized but not eliminated), the optical path difference becomes predictable and manageable, improving measurement precision without requiring complex compensation mechanisms.
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 provides stable, repeatable, and easy-to-manufacture measurements with improved dynamics and sensitivity, allowing for the detection of multiple substances using a single measurement setup and easy replacement of probes, while simplifying analysis through high-frequency interference fringes and a single cavity model.
Implementation Method 1
An interferometric fiber optic sensor includes a Michelson interferometer with one arm covered with active substance adapted to interact with a substance to be detected. A result of this interaction is a change of thickness or optical thickness of the active substance, refractive index, or optical attenuation at the end of measurement arm.
Implementation Method 2
a measuring element with a resonant cavity having a face adapted to come into contact with a chemical substance to be detected
Data Source
AI summary
Disclosed is an interferometric fiber optic sensor for detecting chemical substances. A light source a detector are connected to a light dividing element in an optical path with an optical fiber segment. The optical fiber segment is further optically coupled with a measuring element across a residual cavity. The measuring element further has a face adapted to be exposed to a test substance that may contain a chemical substance to be detected. The optical fiber segment and the measuring element can be held together so that there is only the residual cavity between them. The optical fiber segment is contained, at least along part of its length, within a capillary. A first end part of the capillary is joined with the measuring element while another portion of the capillary is joined or clenched on the optical fiber segment, so that the capillary, the optical fiber segment and the measuring element together form a fiber optic measuring probe as a part of the optical path with the light source and detector.