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掺铒光纤芯棒螯合物化学气相沉积系统如图 1所示[21]。该沉积系统由螯合物高温供料系统和改进型化学气相沉积设备组成。其中铒的螯合物Er(thmd)3经高温加热保温后,由氦气携带进入石英反应管内,并在反应管内与氧气等原料发生化学反应后沉积于石英管内壁,后在氢氧焰的高温加热下玻璃化,形成光纤芯棒的芯层。
反应由于Er3+在纯二氧化硅中的溶解度较低,实验中采用Al3+进行共同掺杂,提高预制棒中铒离子掺杂浓度,并降低因Er3+高浓度掺杂引起的团簇效应。其中,Al3+由AlCl3气体与O2反应后的Al2O3提供。为使Er(thmd)3和AlCl3能够充分气化,需将Er(thmd)3和AlCl3分别加热至190 ℃~200 ℃和130 ℃~140 ℃。同时因Er(thmd)3和AlCl3的气体浓度与其容器的温度正相关,为了稳定进入反应管中螯合物和AlCl3浓度,需在螯合物高温供料系统温度到达预设值后保温1 h以上。基于该工艺方案,本文中制备了Al-Er共掺和Al-Ge-Er共掺两种光纤,纤芯芯层制备参数设定值如表 1所示。反应管采用Heraeus的F300系列,并在芯层沉积前预沉积数层由SiO2-P2O5构成的隔离层,用于减少反应管和氢氧焰中羟基扩散进入芯层,防止由此引起的本底损耗升高。
表 1 掺铒光纤制备参数
Table 1. Parameters of erbium-doped fiber fabricating
doping type deposition temperature/℃ Er(thmd)3 gas flow/
(mL·min-1)AlCl3 gas flow/
(mL·min-1)SiCl4 gas flow/
(mL·min-1)GeCl4 gas flow/
(mL·min-1)number of passes Al-Er 1940 120 225 110 0 2 Al-Ge-Er 1940 120 160 110 200 2 依照掺铒光纤纤芯直径与包层直径的设计比例,选定合适的石英管套管,将掺铒光纤芯棒经加套处理后制作成掺铒光纤预制棒,最后使用光纤拉丝塔将其拉制成直径为125.0 μm±1.0 μm的掺铒光纤。
基于气相沉积法的掺铒光纤制备与温度特性
Fabrication and temperature characteristics of erbium-doped fiber based on chemical vapor deposition
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摘要: 为了研制温度稳定性满足中高精度光纤陀螺仪中超荧光光源使用要求的掺铒光纤, 采用螯合物气相沉积法制备了Al-Er共掺和Al-Ge-Er共掺两种掺铒光纤。同时对两种光纤的吸收系数和本底损耗进行了测试研究, 并搭建超荧光光源测试平台, 对Al-Ge-Er共掺光纤的温度稳定性进行了实验验证。结果表明, 在制备光纤时通入等量的铒的螯合物, Al-Er共掺光纤具有更高的吸收系数, 但本底损耗较高; 两种光纤在1530 nm的吸收系数分别为35.6 dB/m和20.0 dB/m, 在1200 nm的本底损耗为31.7 dB/km和6.3 dB/km; 在-45.0 ℃~70.0 ℃变温范围内, Al-Ge-Er共掺光纤的自发辐射光谱在中心波长为1560.84 nm, 10.51 nm带宽的平均波长变化约为6.52×10-7 nm/℃, 该光纤可满足高精度光纤陀螺的超荧光光源使用要求。该研究为掺铒光纤的研制提供了参考。Abstract: In order to develop erbium-doped fibers with temperature stability to achieve the requirements of super-fluorescent light sources for medium and high precision fiber optic gyroscopes, two types of erbium-doped fibers, Al-Er co-doped and Al-Ge-Er co-doped were prepared by a chelate vapour deposition method. The absorption coefficients and background losses of the two fibers were measured, and the temperature stability of the Al-Ge-Er co-doped fibers was verified experimentally by building a test platform for the super fluorescent light source. The study shows that the Al-Er co-doped fibers have higher absorption coefficients but worse background losses when they are fabricated with an equal volume of erbium chelate. The absorption coefficients of the two fibers are 35.6 dB/m and 20.0 dB/m at 1530 nm, and the background losses are 31.7 dB/km and 6.3 dB/km at 1200 nm. In the temperature range of -45.0 ℃~ 70.0 ℃, the spontaneous emission spectrum mean wavelength variation of the Al-Ge-Er co-doped fiber fabricated by chelate vapor deposition method is about 6.52×10-7 nm/℃ at the central wavelength of 1560.84 nm with the bandwidth of 10.51 nm. This fiber can achieve the requirements of a super-fluorescent light source for high precision fiber optic gyroscope. And this study provides a reference for the development of erbium-doped optical fibers.
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表 1 掺铒光纤制备参数
Table 1. Parameters of erbium-doped fiber fabricating
doping type deposition temperature/℃ Er(thmd)3 gas flow/
(mL·min-1)AlCl3 gas flow/
(mL·min-1)SiCl4 gas flow/
(mL·min-1)GeCl4 gas flow/
(mL·min-1)number of passes Al-Er 1940 120 225 110 0 2 Al-Ge-Er 1940 120 160 110 200 2 -
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