中红外空心Bragg光纤的制备及在气体传感中的应用

Fabrication of mid-infrared hollow-core Bragg fiber and it application in gas sensing

空心Bragg光纤可广泛用于气体传感,但要求它的传输通带处于中红外波段,以便与待测气体的基频吸收峰匹配.本文提出了空心Bragg光纤传输通带的一种设计方法与波长控制工艺,可以实现传输通带在2.5-12μm内任意波长的空心Bragg光纤的制备.实验制备出一阶传输通带分别在10.6μm和3.3μm的光纤样品,利用截断法测量出其一阶传输通带损耗分别为5.9 dB/m和8.8 dB/m.利用在传输通带在3.3μm的样品中注入和排出甲烷/氮气混合气体,观察到了光纤样品透射谱随注入气体浓度的变化,并用指数稀释法初步测量了该系统的浓度探测极限约为26 ppm,验证了该光纤应用于气体传感的可行性.

In its application of gas sensing, the transmission band of the hollow-core Bragg fiber should match the main absorption peak of the target gas. In this paper, we introduce the design method of the hollow-core Bragg fiber transmission band and develop a fabrication process supporting its transmission band control. Fiber samples with fundamental transmission bands at 10.6 μm and 3.3 Ixm are fabricated, whose transmission losses are 5.9 dB/m and 8.8 dB/m, respectively, measured by the cut-back method. Utilizing the fiber sample with a transmission band of 3.3 gm, the injection and the expulsion of CH4/N2 gas are realized and observed by the change of fiber transmission spectrum. The detection limit of the experimental system is measured to be 26 ppm for CH4 by exponential dilution method, demonstrating the feasibility of hollow-core Bragg fiber in its application of gas sensing.