Ultra-Weak Fiber Bragg Grating Network for Small Fire Source Detection
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Solution Overview
Problem
Current optical fiber grating sensing technologies face challenges in achieving long-distance, large-capacity, and high-density small-scale fire source monitoring due to limitations in multiplexing capacity and spatial resolution, particularly with traditional FBG sensor networks using wavelength division multiplexing (WDM) and time division multiplexing (TDM) technologies.
Innovation Solution
The method involves creating an ultra-weak fiber Bragg grating (UWFBG) sensor network with FBGs engraved at equal intervals on a single optical fiber, dividing the network into larger areas, and using pulsed light with a wider pulse width to obtain overall spectral information, allowing for improved spatial resolution and detection of small-scale fire sources without increasing hardware circuit requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple FBGs with strong reflectivity of different wavelengths are welded in series to form a sensor network using WDM technology, then small-size fire source detection capability is improved, but the multiplexing capacity is limited to only a few dozen
Solution Approach 1:
The patent divides the optical fiber sensing network into multiple sensing zones along the fiber length, with each zone containing multiple FBG sensors. This segmentation allows the system to handle large numbers of sensors (thousands) while maintaining the ability to detect small fire sources through zone-based spectral analysis
Solution Approach 2:
The patent transitions from traditional point-by-point FBG detection to a dimensional approach where FBGs are grouped into spatial zones. By analyzing the superimposed spectral information from multiple FBGs within each zone, the system achieves both high multiplexing capacity and small fire source detection capability across the entire fiber length
2Quantity of substance
If multiple FBGs with the same wavelength and weak reflectivity are welded in series to form a sensor network using TDM technology, then the multiplexing capacity can reach hundreds, but the interval between FBGs is limited to meter level
Solution Approach 1:
The patent segments the fiber into sensing zones with much smaller intervals (centimeter to decimeter level) compared to traditional TDM. By using optical time domain reflectometry (OTDR) technology, the system can distinguish signals from closely spaced FBGs within each zone, enabling high multiplexing capacity with reduced intervals
Solution Approach 2:
The patent employs periodic pulsed light illumination to sequentially excite FBGs at different positions along the fiber. The reflected signals are detected and analyzed in time sequence, allowing the system to resolve closely spaced FBGs while maintaining high multiplexing capacity through time-resolved spectral analysis
3Measurement precision
If the interval between FBGs is reduced to detect small-sized fire sources, then small fire source detection capability is improved, but the pulse width of pulsed light source and bandwidth of hardware circuit limit the minimum interval
Solution Approach 1:
The patent introduces spatial zonal grouping as an additional dimension to the detection system. Instead of requiring ultra-short pulse widths to resolve individual closely-spaced FBGs, the system groups them into zones and analyzes their superimposed spectral signatures, thereby achieving small fire source detection without extreme hardware bandwidth requirements
Solution Approach 2:
The patent merges the spectral information from multiple FBGs within each sensing zone to form a composite spectral signature. This merging approach allows the system to detect small temperature changes affecting individual FBGs or small groups of FBGs, achieving high spatial resolution without requiring hardware capable of resolving each individual FBG separately
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 enhances the multiplexing capacity and perception resolution of the UWFBG sensor network, enabling effective long-distance detection and rapid monitoring of small-scale fire sources with increased accuracy and response speed.
Implementation Method 1
The technology based on Fiber Bragg Grating (FBG) temperature sensing is a mature technology in the fire detector market. The temperature of the FBG's center wavelength is sensitive to temperature to measure the temperature of the area where the FBG is located
Implementation Method 2
inputting a pulsed optical signal into the identical UWFBG sensor network, a pulse width of a single pulsed optical signal covers all FBGs in an area
Data Source
AI summary
An optical fiber grating sensing method applied to small-scale fire source monitoring are provided, distinguishing two concepts of a spatial resolution and a perception resolution, under the premise of ensuring the spatial resolution of a traditional fiber Bragg grating sensing system, only increase the number of fiber Bragg gratings covered by a single pulsed optical signal without changing a pulse width of a pulsed optical signal, so as to improve the perception resolution of the system without increasing the requirements for a hardware circuit, and truly shorten an interval between adjacent fiber Bragg gratings. Improving the perception resolution of the system, which not only ensures the spatial resolution of the system, but also realizes the monitoring of small-scale fire sources; by adopting a simple feature extraction algorithm to obtain fire temperature information in different areas, the temperature detection speed of the system is fast.