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Distributed time delay sensing in a random fiber grating array based on chirped pulse φ-OTDR
Optics Letters
|July 8, 2020
Summary
A novel chirped pulse phase optical time domain reflectometry (CP φ-OTDR) system uses a random fiber grating array for high-precision distributed temperature sensing. This method directly measures time delay variations caused by temperature changes, achieving 0.028°C sensitivity.
Area of Science:
- Photonics and Optical Sensing
- Fiber Optic Sensing Technology
- Distributed Temperature Measurement
Background:
- Conventional φ-OTDR systems measure distributed phase changes, often requiring ultra-narrow linewidth lasers.
- Temperature variations induce changes in refractive index and fiber dimensions, affecting optical signal characteristics.
- Distributed sensing requires precise measurement of subtle physical parameter changes along optical fibers.
Purpose of the Study:
- To propose and demonstrate a high-precision distributed time delay measurement technique for temperature sensing.
- To leverage a random fiber grating array within a CP φ-OTDR system for enhanced sensing capabilities.
- To achieve real-time, high-resolution distributed temperature measurements.
Main Methods:
- Utilizing a chirped pulse phase optical time domain reflectometry (CP φ-OTDR) system.
- Employing a random fiber grating array with sub-micron inscribed refractive index change locations.
- Measuring localized backscattered speckle pattern changes and performing cross-correlation calculations.
- Using a megahertz bandwidth distributed feedback laser for real-time measurements.
Main Results:
- Demonstrated high-precision distributed time delay measurement for temperature sensing.
- Achieved a minimum detectable temperature variation of approximately 0.028°C.
- Obtained meter-order spatial resolution with stable, low-fluctuation time-resolved localized pattern traces.
- Successfully correlated temperature-induced spectral response changes with physical parameter variations.
Conclusions:
- The proposed CP φ-OTDR system with a random fiber grating array enables direct, real-time measurement of distributed time delay for accurate temperature sensing.
- The system offers significant advantages over conventional methods by directly measuring time delay instead of phase, enhanced by the random grating's properties.
- This technique provides a robust and sensitive solution for distributed temperature monitoring with potential applications in various fields requiring precise thermal management.
