This study is focused on the fiber Bragg gratings central resonant wavelength thermal stability, fabricated by the point-by-point inscription method, using an infrared femtosecond laser. A new methodology is proposed to analyze the refractive index decay using the central wavelength shift of fiber Bragg gratings, executing stepped and continuous annealing regimes up-to a maximum temperature of 800 °C. The obtained thermal refractive index decay follows a typical power-law function, and from the theoretical model fit to the experimental data was possible to simulate and predict the refractive index decay over a large time period, up-to 1000 years. With the proposed approach it is possible to adjust the fiber Bragg gratings pre-treatment conditions to ensure effective operation during a certain time period, at a specific working temperature, without any degradation. An experimental method to mitigate this decay is proposed, and the results demonstrate the high potential of using infrared femtosecond inscribed fiber Bragg gratings for high temperature monitoring.

中文翻译：

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飞秒激光器产生的光纤布拉格光栅的谐振波长热稳定性

这项研究的重点是光纤布拉格光栅的中心谐振波长热稳定性，该光栅使用红外飞秒激光器通过逐点刻录方法制造。提出了一种使用光纤布拉格光栅的中心波长偏移来分析折射率衰减的新方法，执行阶梯式和连续退火方案，最高温度可达 800 °C。获得的热折射率衰减遵循典型的幂律函数，并且从理论模型拟合到实验数据可以模拟和预测长达 1000 年的大时间段的折射率衰减。通过所提出的方法，可以调整光纤布拉格光栅的预处理条件，以确保在特定时间段内在特定工作温度下有效运行，没有任何退化。提出了一种减轻这种衰减的实验方法，结果证明了使用红外飞秒内接光纤布拉格光栅进行高温监测的巨大潜力。