不同包层直径的倾斜光纤光栅折射率传感特性

倾斜光纤光栅的透射谱中有纤芯模和大量的包层模,它们具有与布拉格光栅相同的温度特性.利用HF酸腐蚀的方法得到具有不同包层直径的倾斜光纤光栅,研究了其对外界折射率的传感特性.结果表明,外界环境折射率在1.333～1.4532之间变化时,同一直径倾斜光纤光栅的高阶包层模的敏感性要比低阶包层模强;随着包层直径的减小,包层模的敏感性增强,且在折射率比较高的环境中有更高的敏感性.因此,利用倾斜光纤光栅的温度特性不仅可以解决温度交叉敏感问题,而且通过小同的腐蚀程度能定制所需要的灵敏度,以实现对环境折射率的高灵敏度测量.该办法可应用于对生物和化学等高灵敏度传感领域的各种溶液进行实时监控.

Refractive Index Sensing Characteristic of Tilted Fiber Bragg Gratings with Different Cladding-Diameters

Short-period fiber Bragg gratings with gratings planes tilted at a weak angle corresponding to the fiber axis show core mode, as well as a large number of cladding-mode resonances in transmission. Tilted fiber Bragg grating (TFBG) with different cladding diameters is achieved after the cladding of the tilted fiber Bragg grating is etched by hydrofluoric, and then the sensitivity of refractive index is investigated. While the surrounding refractive index changes from 1.333 to 1.4532, the high-order cladding modes are more sensitive than the low-order ones for the same diameter. The sensitivity of the cladding modes is enhanced with the decrease of cladding diameter, and it is custom-built more sensitive to surrounding refractive index. Therefore, this way not only can solve temperature-crossing sensitivity problem, but also can satisfy the custom-built sensitivity in the real-time monitoring systems by etching the clad of TFBG in different degrees. It can be applied to biochemical environmental sensing and concentration measurement of chemical solutions.