Fiber Bragg gratings in hydrogen-loaded photosensitive fiber with two regeneration regimes

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• 作者：Leonhard Polz ; Quang Nguyen ; Hartmut Bartelt ; Johannes Roths
• 关键词：Fiber Bragg grating ; Regenerated grating ; Chemical composition grating ; High temperature gratings
• 刊名：Optics Communications
• 出版年：15 February, 2014
• 年：2014
• 卷：313
• 期：Complete
• 页码：128-133
• 全文大小：1808 K

文摘

In a highly Ge-doped photosensitive fiber co-doped with phosphorus and fluorine and with a doped inner cladding, we observed, during annealing experiments, an anomalous variation of the FBG strength as a function of temperature and time. This characteristic only occurred when the fiber had been loaded with hydrogen. During a stepwise temperature increase from room temperature to 1200 掳C with 15 min dwell times, the gratings showed, after an initial thermal decay, in two distinct temperature ranges a significant increase in reflectivity with time. One range with an increase in reflectivity was found between 850 掳C and 1000 掳C. The behavior of the FBGs in this range was very similar to that known from chemical composition or regenerated gratings. Another temperature range with increasing reflectivity was found between 500 掳C and 700 掳C, followed by a strong decrease in reflectivity at temperatures between 750 掳C and 800 掳C. Both regimes of regeneration might be associated with changes in the core and the doped inner cladding of this type of fiber. At different temperatures the drift behavior of and was investigated. In specific temperature regions a positive wavelength drift combined with a decrease in has been observed. This is in contradiction to the standard thermal decay model and seems to be a characteristic of regenerated gratings.