Multi-gap EFPI Sensor Eliminates Solution Jumps
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Solution Overview
Problem
Existing EFPI sensors face errors due to misinterpretation of sinusoidal interference patterns, known as 'solution jumps,' which prevent them from being absolute sensors, and are challenged by the harsh downhole environment of high temperatures and pressures.
Innovation Solution
A multi-gap EFPI sensor system with at least three gaps, including an air gap and two solid material gaps, is designed to reduce errors by providing multiple reflection surfaces, allowing for precise estimation of gap widths using curve fitting algorithms, and is fabricated as a micro-electromechanical system (MEMS) to withstand extreme conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single-gap EFPI sensor is used, then the device complexity is low, but solution jumps occur leading to reduced measurement precision
Solution Approach 1:
The single optical gap is segmented into multiple optical gaps (first optical gap, second optical gap, third optical gap) with different characteristics. Each gap produces its own interference pattern, and by combining these multiple patterns, the system eliminates solution jumps and achieves continuous, precise measurements without requiring complex external reference systems.
2Reliability
If traditional EFPI sensor structure is used, then ease of manufacture is good, but reliability in harsh downhole environment is reduced
Solution Approach 1:
The optical fibers are nested within a protective tubular structure that provides mechanical strength and environmental protection. The multiple optical gaps are nested within the same fiber bundle, with each gap formed by precise positioning of reflective elements. This nested configuration protects the sensitive optical components while maintaining a compact, manufacturable structure suitable for harsh downhole environments.
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 multi-gap sensor system reduces solution jumps and provides accurate, high-precision measurements of properties like pressure and temperature by utilizing multiple reflection surfaces and advanced fabrication techniques, ensuring reliable operation in harsh downhole environments.
Implementation Method 1
The first reflection output light interferes with the second reflection output light to create an interference pattern or interferogram that depends on a difference in the optical path lengths
Implementation Method 2
The input light enters the single mode optical fiber and is partially reflected by a first glass-to-air interface to produce first reflected output light
Implementation Method 3
A Fabry-Perot (FP) cavity is formed between the ends of the optical fibers within the capillary tube
Data Source
AI summary
An apparatus for estimating a property includes a hollow core tube and an input light guide disposed at least partially within hollow core tube. The apparatus also includes a second gap disposed within the hollow core tube and separated from the input light guide by an air gap width. The second gap is formed of a first solid material and has a second gap width. The apparatus also includes a third gap disposed at least partially within the hollow core tube and being further from the input light guide than the second gap. The third gap is formed of a second solid material and has a third gap width.