Optical Fiber Delay Span for FBG Calibration Data Separation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical sensor systems face challenges in accurately converting optical signal indicators into engineering units, such as temperature, strain, and pressure, due to the need for separate coefficients for each sensor, which can lead to errors and are not always feasible to update, especially in high-design-assurance applications.
Innovation Solution
The system employs a single optic fiber with a set of fiber Bragg gratings (FBGs) and an optical sensor, where a delay span between the FBGs and the optical sensor allows for the separation of FBG returns and sensor returns. The interrogator receives these returns, decodes the encoded calibration coefficient data from the FBGs, and converts the combined returns into engineering units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate coefficients are stored in a database for each sensor, then conversion accuracy is improved, but system complexity and error risk increase due to manual database updates
Solution Approach 1:
The sensor embeds its own calibration coefficients within the optical fiber structure, allowing the sensor to self-identify and self-calibrate without external database updates. The interrogator reads the coefficients directly from the fiber, eliminating manual database maintenance while maintaining high conversion accuracy.
Solution Approach 2:
The calibration coefficients are nested within the optical fiber structure itself, specifically encoded in the reflectance characteristics of FBGs or modulation patterns in the fiber. This nesting allows the coefficients to be carried with the sensor permanently, eliminating the need for separate database storage and updates.
2Adaptability or versatility
If coefficients are encoded with the sensor itself, then ease of sensor replacement is improved, but difficulty in separating coefficient data from sensor reflections increases
Solution Approach 1:
The optical fiber is segmented into distinct functional regions: FBGs for encoding coefficients, delay spans for temporal separation, and sensing regions for measurements. This segmentation allows the interrogator to temporally separate coefficient reading from sensor measurement, solving the data separation problem while maintaining sensor replaceability.
Solution Approach 2:
The system performs preliminary action by reading the coefficient data from the FBGs before performing the actual sensor measurement. The delay span ensures that coefficient extraction is completed first, then the sensor reflection is measured separately, eliminating the need for complex real-time separation algorithms.
3Ease of manufacture
If traditional techniques are used for data transmission, then hardware costs are reduced by using the same optical channel, but measurement precision deteriorates due to inability to separate coefficient and sensor data
Solution Approach 1:
The interrogator uses periodic scanning of the optical fiber, first measuring reflectance at wavelengths corresponding to FBG coefficients, then measuring at wavelengths corresponding to sensor reflections. This periodic action with wavelength multiplexing allows separation of coefficient and sensor data using the same optical channel, maintaining low hardware cost while achieving high measurement precision.
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 accurate conversion of optical signals into engineering units without the need for central coefficient storage, allowing sensors to be added or replaced without software updates, and facilitates the use of the same optical channel for both coefficient data and sensor data.
Implementation Method 1
A set of fiber Bragg grating (FBGs) is formed in the optic fiber between the first end and the optical sensor. The FBGs are configured for reflecting FBG returns of the illumination back along the optic fiber to the first end.
Implementation Method 2
Fiber optic sensors (FOS) including, but not limited to fiber Bragg gratings (FBGs) and Fabry-Perot interferometers (FPIs) are used for many applications due to their small size, corrosion resistance, and immunity to electromagnetic interference.
Implementation Method 3
A delay span is included in the optic fiber between the FBGs and the optical sensor. The delay span has a length along the fiber that is configured to create a delay between when the interrogator receives the FBG returns and when the interrogator receives the sensor return.
Data Source
AI summary
A system includes an illuminator. A first end of an optic fiber is operatively connected to the illuminator for transmitting illumination along the length of the optic fiber. An optical sensor operatively connected to the second end for reflecting sensor returns of the illumination back along the length of the optic fiber. A set of fiber Bragg grating (FBGs) is formed in the optic fiber between the first end and the optical sensor. A delay span is included in the optic fiber between the FBGs and the optical sensor. An interrogator is operatively connected to the first end to receive the sensor returns and the FBG returns from the optic fiber. The delay span has a length along the fiber that is configured to create a delay between when the interrogator receives the FBG returns and when the interrogator receives the sensor return.