Broadband Fiber Sensor Array Using Local Perturbations
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Solution Overview
Problem
Existing fiber sensor arrays face limitations in high temperature applications due to degradation of UV-inscribed gratings and the difficulty in separating individual sensor contributions in broadband Mach-Zehnder interferometer systems, requiring expensive optical analyzers and lacking robustness under extreme conditions.
Innovation Solution
A broadband fiber sensor array is formed by introducing local perturbations along an optical fiber, where each sensing element functions as a Mach-Zehnder interferometer, transforming signal modes and allowing for individual parameter determination from a single output transmission spectrum, using unique perturbations such as diameter variations or refractive index changes, enabling accurate measurement of temperature, pressure, and refractive index without the need for expensive analyzers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If UV-inscribed fiber Bragg gratings are used in sensor arrays, then individual resonance wavelengths can be monitored with narrow spectral resolution, but the gratings degrade at high temperatures and become unstable
Solution Approach 1:
The patent changes the operating parameter from narrowband resonance detection to broadband interference detection. By using Mach-Zehnder interferometers that operate across a broad spectral range rather than relying on narrow UV-inscribed Bragg gratings, the system achieves high-temperature stability while maintaining measurement capability through unique broadband transmission spectra for each sensor element
Solution Approach 2:
The patent substitutes the physical mechanism of UV-inscribed grating resonance with Mach-Zehnder interferometer broadband interference. This replacement eliminates the temperature-sensitive grating structure while preserving the ability to distinguish individual sensors through spectral analysis of unique interference patterns
2Reliability
If broadband Mach-Zehnder interferometer sensors are used, then high temperature robustness is achieved, but individual sensor contributions cannot be separated from the overlapping broadband spectra
Solution Approach 1:
The patent applies local quality by giving each Mach-Zehnder interferometer sensor element a unique broadband transmission spectrum through local perturbations in the optical fiber. This uniqueness allows individual sensor identification and signal separation despite the broadband overlapping nature of the interference patterns
Solution Approach 2:
The patent transitions from narrowband wavelength discrimination to broadband spectral shape analysis. By utilizing the entire broadband spectrum and analyzing unique spectral shapes rather than narrow resonance peaks, the system enables separation of individual sensor contributions through multidirectional spectral decomposition
3Productivity
If fiber Bragg grating sensor arrays are used, then individual resonance shifts can be determined from a single spectral measurement, but expensive optical analyzers with fine spectral resolution are required
Solution Approach 1:
The patent replaces expensive, high-resolution optical analyzers required for narrowband FBG detection with simpler, lower-cost broadband spectral measurement systems. The unique broadband transmission spectra of Mach-Zehnder interferometers can be resolved using less sophisticated equipment, reducing system cost and complexity
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 allows for robust, high-temperature operation with accurate determination of multiple sensing parameters from a single measurement, using a single light source and optical spectrum analyzer, while maintaining the broadband attributes of Mach-Zehnder interferometer systems and providing individual sensor results similar to fiber Bragg grating arrays.
Implementation Method 1
each sensing element transforming at least a fraction of the mode of a propagating signal into higher order modes and then back again into the original propagating mode
Implementation Method 2
A Mach-Zehnder interferometer (MZI) type of sensor does not use resonance wavelength analysis and is considered to be more broadband than an FBG sensor
Data Source
AI summary
A broadband fiber optic sensor array is formed along a length of single mode optical fiber, with the individual sensing elements formed by introducing local perturbations (e.g., changes in diameter) along the length of the optical fiber. The sensor array requires only a single light source input and a single (conventional) optical spectrum analyzer output and is capable of providing individual measurements (such as local temperature or pressure) for each sensing element disposed along the length of fiber. The individual transmission spectra of the sensing elements forming the array are smooth and strongly overlap, and a method has been developed for determining the characteristics of the individual elements from the variations in the total (combined) transmission spectrum.