Chirped Bragg Grating Sensor Group Delay Measurement
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Solution Overview
Problem
Existing methods for sensing temperature, humidity, or mechanical stress using fiber Bragg gratings require complex setups and are not easily applicable for simultaneous measurement at multiple locations.
Innovation Solution
An optical sensor comprising a chirped Bragg grating and an optical reference reflector, where the group delay between partial reflection signals is used to measure the parameter of interest, allowing for simpler and more versatile sensing across different locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a spectrometer is used to measure Raman shift frequencies or reflected signal spectrum, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts the essential measurement function from the complex spectrometer system and implements it using a simple autocorrelation detector that only requires a single photodetector and electronic correlation measurement. This removes the need for complex optical spectrum analysis hardware while maintaining the ability to measure temperature-induced changes in the chirped FBG reflection characteristics.
Solution Approach 2:
The patent replaces the optical mechanical system (spectrometer with moving parts and complex optical paths) with an electronic measurement system that uses autocorrelation detection. The measurement is performed in the electrical domain rather than requiring complex optical dispersion analysis, thereby simplifying the device while maintaining precision.
2Measurement precision
If a Kerr phase interrogator with tunable laser and optical amplification is used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts the core measurement capability from the complex Kerr phase interrogator system and implements it using a simplified autocorrelation detection method. The essential function of measuring phase changes is achieved through electronic autocorrelation of the reflected signal, eliminating the need for tunable lasers, optical amplifiers, and complex phase modulation machinery.
Solution Approach 2:
The patent replaces expensive, complex, and maintenance-intensive components (tunable lasers, optical amplifiers, Kerr cells) with a simple, robust autocorrelation detector using standard photodetectors and electronic circuitry. This substitution maintains measurement precision while dramatically reducing system complexity and cost.
3Adaptability or versatility
If multiple chirped FBGs are used to measure temperature at multiple locations, then versatility is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple sensing functions into a single integrated measurement system. By using a common autocorrelation detector that can analyze the reflection characteristics of multiple chirped FBGs sequentially or in parallel through wavelength division, the system achieves multi-location temperature sensing without requiring separate measurement setups for each sensor.
Solution Approach 2:
The patent creates a universal measurement apparatus that can accommodate and analyze multiple types of sensors (chirped FBGs at different locations) using the same autocorrelation detection methodology. The single photodetector-based system can measure temperature at multiple locations by appropriately configuring the optical paths and analysis algorithms, eliminating the need for location-specific measurement systems.
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
This approach enables efficient and accurate measurement of temperature, humidity, or mechanical stress with a less complex setup, allowing for distributed sensing and continuous monitoring of parameters like temperature or mechanical stress in large objects.
Implementation Method 1
a chirped Bragg grating (100) and an optical reference reflector (122) provided within an optical path... a second partial reflection signal (Sr2) created by the chirped Bragg grating (100)
Implementation Method 2
an optical reference reflector (122) provided within an optical path... a first partial reflection signal (Sr1) created by the optical reference reflector (122)
Data Source
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AI summary
The invention relates to a method for optically sensing a parameter of the group of temperature, humidity or mechanical stress using at least one optical sensor, the at least one optical sensor (120) comprising a chirped Bragg grating (100) and an optical reference reflector (122), the method comprising the steps of creating at least one optical probing signal (Sprobe) having a predetermined center wavelength and a bandwidth that lies, for the whole range of the parameter (P) to be sensed, within the reflection bandwidth of the chirped Bragg grating (100), feeding the at least one optical probing signal (Sprobe) to the at least one optical sensor (120), receiving at least one optical reflection signal created by the at least one optical sensor (120), wherein the at least one optical reflection signal comprises, for each of the at least one optical sensor (120), a first partial reflection signal (Sr1) created by the optical reference reflector (122) and a second partial reflection signal (Sr2) created by the chirped Brag grating (100) of the respective at least one optical sensor (120), measuring the group delay (τg) between the first and second partial reflection signal (Sr1, Sr2) created by each of the at least one optical sensor (120), and determining, for each of the at least one optical sensors (120), an absolute or relative value of the at least one parameter (P) using the group delay (τg) measured and a reference information. The invention further relates to a sensor arrangement for implementing the method as well as to an optical sensor that is suitable for being used in such a sensor arrangement.