Optical Fiber Calibration Device for Distributed Sensing
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Solution Overview
Problem
Existing calibration methods for optical time-domain reflectometers are limited to distance measurement and do not allow for the calibration of important parameters such as spatial resolution, temperature, strain, or vibrations, which are crucial for accurate distributed sensing technologies.
Innovation Solution
A calibration device and process that utilize an optical fiber with different optical paths of varying lengths, including a loop configuration with a coupler and optical amplifier, and a continuous probe signal to analyze Brillouin backscattered signals, enabling the measurement of temperature and strain along the fiber by stimulating Brillouin scattering and scanning the probe frequency to find the Brillouin gain peak.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing calibration methods using recirculating delay lines are used, then distance measurement calibration is achieved, but calibration of spatial resolution, temperature, strain, and vibrations is not possible
Solution Approach 1:
The calibration device is designed to perform multiple calibration functions simultaneously - distance measurement, spatial resolution, temperature, strain, and vibrations - by integrating various sensing technologies into a single fiber optic calibration system, allowing one device to serve multiple calibration purposes that previously required separate systems
Solution Approach 2:
The device segments the calibration process into distinct functional modules including a recirculating delay line for distance calibration, a Brillouin scattering section for spatial resolution and temperature/strain calibration, and a Raman scattering section for temperature calibration, allowing each segment to be optimized for its specific calibration function while working together as an integrated system
2Adaptability or versatility
If optical fiber with multiple scattering processes is used, then comprehensive sensing parameters can be calibrated, but device complexity increases
Solution Approach 1:
The calibration device employs a nested structure where the recirculating delay line contains the Brillouin scattering section, which in turn contains the Raman scattering section. This nested configuration allows multiple sensing technologies to be integrated within each other, sharing common optical paths and components while maintaining distinct calibration functions for each scattering process
Solution Approach 2:
The patent introduces intermediary components such as optical circulators, couplers, and isolators that mediate between different scattering processes and the pump/probe signals. These intermediaries manage the complex interactions between multiple optical paths and scattering mechanisms, enabling comprehensive calibration while maintaining system organization and controllability
3Measurement precision
If pump and probe signals are used for Brillouin scattering calibration, then temperature and strain measurement is enabled, but signal analysis complexity increases
Solution Approach 1:
The device performs preliminary calibration actions by first establishing the Brillouin frequency shift baseline through pump-probe signal interaction in the Brillouin scattering section. This preliminary measurement of the Brillouin frequency shift creates a reference that simplifies subsequent temperature and strain measurements, as the system already has the scattering characteristics calibrated before actual sensing begins
Solution Approach 2:
The system implements feedback mechanisms where the detected Brillouin backscattered signal is analyzed to determine temperature and strain conditions. The measured Brillouin frequency shift feeds back into the calibration process, allowing the system to adjust and refine its measurements based on the actual scattering characteristics observed, thereby simplifying the overall analysis through iterative refinement
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 allows for the calibration of distributed sensing technologies beyond distance measurement, providing accurate spatial resolution and temperature/strain information along the optical fiber, enhancing the precision of distributed sensing systems.
Implementation Method 1
an optical amplifier arranged for amplifying the pump signal traveling in the loop
Implementation Method 2
Brillouin scattering is the interaction of a light pulse with thermally excited acoustic waves (also called acoustic phonons). Acoustic waves, through the elasto-optic effect, slightly and locally modify the index of refraction. The corresponding moving grating reflects back a small amount of the incident light and shifts its frequency (or wavelength) due to the Doppler Effect.
Implementation Method 3
an optical amplifier arranged for amplifying the pump signal traveling in the loop with a gain equal or less than a loss in the loop during one complete circulation of the pump signal in the loop
Data Source
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AI summary
The invention concerns a device (10) for calibrating distributing sensing technologies. The device (10) comprises an optical fiber (8), a first input (11) arranged for receiving at least one optical pulse (5) and injecting this at least one optical pulse towards the optical fiber (8), an output (13) arranged for receiving a backscattered signal generated in the optical fiber. The optical fiber (8) comprises at least one event (9), each event being a part of the optical fiber (8) and having at least one modified physical state or property that is different from the physical state or property of the rest of the optical fiber. The device comprises means (7) for creating different optical paths for the at least one optical pulse (5), the different optical paths having different lengths, each optical path passing through the at least one event (9). The invention also relates to a process implemented in device (10).