Serial Weak FBG Interrogator Using Optical Frequency Comb
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Solution Overview
Problem
Existing methods for multiplexing Fiber Bragg Gratings (FBGs) are complex and costly, often relying on tunable lasers with nonlinear wavelength tuning and lack real-time laser calibration, limiting their multiplexing capacity and accuracy in sensing applications.
Innovation Solution
The use of an optical fiber interferometer, specifically a Fabry-Perot interferometer with broadband partial reflectors, for real-time laser calibration and multiplexing of FBGs, enabling accurate determination of laser output power and wavelength, and allowing for the interrogation of a large number of FBGs with improved sensitivity and reduced system complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If tunable lasers with nonlinear wavelength tuning are used for FBG multiplexing, then wavelength tuning capability is achieved, but system complexity and cost increase
Solution Approach 1:
The patent introduces an optical frequency comb as an intermediary element that converts a single-frequency laser into multiple frequency components. This comb structure acts as a mediator between the simple single-frequency laser and the requirement for multiple wavelengths, enabling FBG multiplexing without needing complex tunable lasers. The frequency comb provides stable, evenly-spaced frequency lines that can simultaneously interrogate multiple FBGs with different Bragg wavelengths.
2Reliability
If traditional FBG multiplexing methods are used, then sensing capability is achieved, but real-time laser calibration is lacking
Solution Approach 1:
The patent implements a feedback mechanism where the optical frequency comb provides a stable reference framework that enables real-time monitoring and calibration of laser wavelength. The comb's fixed frequency lines serve as reference points against which FBG reflections are measured, allowing the system to continuously校准 wavelength drift and maintain high measurement precision without requiring complex external calibration equipment.
3Quantity of substance
If a large number of FBGs are multiplexed, then distributed sensing coverage is improved, but signal detection difficulty increases
Solution Approach 1:
The patent segments the optical spectrum into multiple discrete frequency channels using the optical frequency comb. Each comb line corresponds to a specific wavelength channel that can be assigned to interrogate a particular FBG or group of FBGs. This spectral segmentation allows the system to handle hundreds of FBGs by distributing them across different frequency channels, thereby managing signal detection complexity through systematic spectral allocation.
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 the successful multiplexing of up to 1,000 FBGs with enhanced accuracy and reduced system complexity, providing real-time calibration and improved sensitivity for various sensing applications, including temperature, strain, and acoustic or vibration measurements.
Implementation Method 1
an optical or optical fiber interferometer that may provide information about the laser output power and wavelength in real-time for laser calibration
Implementation Method 2
When a broadband light is launched into an FBG, only the light at the resonance wavelength, which is also known as the Bragg wavelength, is reflected
Data Source
AI summary
A serial weak FBG interrogator is disclosed. The serial weak FBG interrogator may include a CW tunable laser or pulsed laser utilized as a laser source and an EDFA. The serial weak FBG interrogator may also be an interrogation of a single sensor system by utilization of a DFB laser which utilizes a single sensor, which may be an interferometer sensor, an extrinsic Fabry-Perot interferometer or a wavelength-modulated sensor. The serial weak FBG interrogator may also include a computer system or CSPU.