蓝宝石光纤高温光学特性研究

Study on Optical Properties of Sapphire Fiber under High Temperature

蓝宝石光纤物理化学性能稳定，熔点高（超过2000℃），在0.3-4.0μm波段范围内透光性好，具有光波导的特点，在高温光纤传感和近红外传感等领域有很好的应用前景.实验从蓝宝石光纤在高温环境下（大于1000℃）的光学稳定性、光纤的自辐射、塑性弯曲对出射光信号的影响3个方面进行研究，结果表明，蓝宝石光纤在高温下的光学传输损耗随时间增加，温度测量精度由信号的稳定性和光纤自辐射决定，而蓝宝石光纤的塑性弯曲引起的信号额外损耗比较小，在900 nm处小于0.1dB.光纤表面在高温下的永久损伤是产生这些性能劣变的主要原因，损伤的主要机制为外部杂质在高温下与光纤表面的相互作用.为了保护蓝宝石光纤传感头在高温下的稳定工作，有必要在光纤表面制作保护层和采用合适的保护套.

With a high melting point （over 2000℃ ）, high transmissions from visible to wavelengths approaching 4 um and favorable mechanical and chemically inert, sapphire fiber is very attractive for high temperature optical fiber sensor and near infrared energy delivery. The performance stability, self-radiation and plastically bend of sapphire fiber under high temperature is studied. Experimental resuhs show the optical transmitter loss is increased with the time when sapphire fiber is under high temperature environments. The influence to high temperature measurement precision is achievable due to the performance stability and self-radiation. The additional loss caused by a single plastically bend is less than 0.1 dB at 900 nm, less than the loss before bend. The permanent injury of the sapphire fiber surface is the main reason of the deterioration. It is found that the surface injury is mainly attributed to the pollution of the fiber surface and the mutual reaction between the sapphire fiber and the polluting substance in the ambient environment. So a suitable protective tube is applied to assure the performance stability.