研究目的
To demonstrate the production of first order off-axis fiber Bragg gratings (FBGs) in a standard single mode fiber (SMF-28e) through femtosecond laser direct writing and characterize their performance in strain, temperature, and curvature sensing applications.
研究成果
The production of first order off-axis FBGs in an SMF-28e through fs-laser direct writing was successfully demonstrated. The fabricated FBGs showed similar strain and temperature sensitivities and exhibited a strong orientation dependence to the plane of curvature. The LP0,1 mode was not sensitive to curvature, while the LP1,1 mode was affected, enabling simultaneous measurement of curvature and temperature.
研究不足
The study found that for temperatures above 240 °C, the reflection spectra of the FBG with a 6.0 μm offset became deformed, limiting the range of temperatures that can be sensed. Additionally, the sensitivity to curvature was found to decrease for off-axis FBGs with smaller reflectivity.
1：Experimental Design and Method Selection:
The study utilized femtosecond laser direct writing to inscribe off-axis FBGs in SMF-28e fibers. The methodology included optimizing the fabrication parameters to achieve desired grating characteristics.
2：Sample Selection and Data Sources:
Standard single mode fibers (SMF-28e, Corning) were used. The fibers were prepared by removing the coating and cleaning with ethanol.
3：List of Experimental Equipment and Materials:
A laser direct writing system with a fiber amplified fs-laser (Satsuma HP, from Amplitude Systèmes), a 100× oil immersion lens (Olympus PLN 100XO), and an optical spectrum analyzer (OSA, model Yokogawa AQ6370D) were among the key equipment used.
4：Experimental Procedures and Operational Workflow:
The fibers were clamped and kept under tension during the writing process. The grating period and length were defined, and the optimal writing conditions were determined. The fabricated FBGs were then characterized for strain, temperature, and curvature sensitivity.
5：Data Analysis Methods:
The spectral variations with each measurand were recorded and analyzed to determine the sensitivity of the FBGs to strain, temperature, and curvature.
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