研究目的
To develop a distributed-optical fiber temperature sensor with enhanced sensitivity using an Al-coated fiber and OFDR, by exploiting the strain-coupled shift in Rayleigh backscattering due to thermal expansion.
研究成果
The Al-coated fiber enhances temperature sensitivity by approximately 56% compared to SMF, due to the higher thermal expansion coefficient of aluminum inducing additional strain. This improvement allows for better temperature resolution in distributed sensing applications, such as structural health monitoring, with potential for further enhancement using other coating materials.
研究不足
The study assumes perfect bonding between the fiber and coating, neglecting radial strain effects, which may lead to discrepancies between theoretical and experimental results. Hysteresis is observed in the Al-coated fiber, and environmental strain isolation is necessary for accurate measurements. The temperature range tested is up to 60°C, and spatial resolution is limited to 5 cm in some experiments.
1：Experimental Design and Method Selection:
The study uses optical frequency-domain reflectometry (OFDR) to measure Rayleigh backscattering (RBS) spectrum shifts. A theoretical model based on force equilibrium and thermal expansion coefficients is developed to predict sensitivity enhancement.
2：Sample Selection and Data Sources:
An Al-coated optical fiber (commercially available from art photonics GmbH) and a standard single-mode fiber (SMF-28) are used as sensing fibers. Data is collected from temperature chambers.
3：List of Experimental Equipment and Materials:
Equipment includes a tunable laser source (Agilent 8164B), optical couplers, polarization controllers, polarization beam splitters, photodetectors, data acquisition board, and temperature chambers (tube-type oven and large commercial oven). Materials include Al-coated fiber and SMF.
4：Experimental Procedures and Operational Workflow:
The OFDR system is set up with a polarization-diversity scheme. The TLS sweeps wavelengths, and RBS signals are detected. Temperature is varied in chambers, and cross-correlation analysis is performed on RBS spectra to measure frequency shifts.
5：Data Analysis Methods:
Data is processed using fast Fourier transform (FFT) and cross-correlation analysis to extract optical frequency shifts, which are calibrated to temperature changes. Linear fitting is used to determine sensitivity.
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