基于微管腔的光纤激光盐度传感研究

Study of optical fiber laser salinity sensor based on microtube cavity

基于光学无源方案的光纤盐度传感器中光与物质的相互作用长度受限,且通常需要单独的流体通道设计,增加了检测复杂度,为此提出了一种基于薄壁微管腔和环腔结构的光纤激光盐度传感器。将薄壁微管腔作为盐度敏感单元和光滤波器,与掺铒光纤相接构成光纤环形谐振腔。通过拉锥光纤耦合在薄壁微管腔激发出回音壁谐振模,其中心波长与盐度线性对应,实现薄壁微管腔内溶液盐度的传感测量。与无增益的微管腔透射谱相比,激光可以提供具有更高信噪比和更窄线宽的传感信号。实验结果表明,在0‰—45‰盐度范围内,提出的光纤激光盐度传感器的传感灵敏度为36.5 pm/‰,线性度达到0.99924,盐度测量误差小于±0.751 3‰,最小探测极限为0.485 5‰,且不需要额外的流体测量通道,有望成为海洋盐度探测的有力工具。

The length of interaction between light and material is limited in the fiber optics salinity sensors based on optical passive scheme, and a separate design of fluid channel is usually required, which increases the detection complexity.Therefore, an optical fiber laser salinity sensor based on thin-walled microtube and ring cavity is proposed.The thin-walled microtube cavity is used as the salinity sensitive unit and optical filter, and is connected with the erbium-doped fiber to form a fiber ring cavity.The whispering gallery mode is excited in the thin-walled microtube cavity through the coupling of tapered optical fibers.The central wavelength is linearly corresponding to the salinity, which realizes the measurement of salinity of solution in the thin-walled microtube cavity.Compared with the transmission spectrum of thin-walled microtube without gain, laser can provide sensing signal with higher signal-to-noise ratio and narrower linewidth.Experimental results show that the sensitivity and the minimum detection limit of the proposed fiber laser salinity sensor are 36.5 pm/‰ and 0.485 5‰,respectively, during the salinity range of 0‰—45‰,the linearity is 0.999 24, and the salinity measurement error is less than ±0.751 3‰,and does not require additional fluid channel, which is expected to become a useful tool for ocean salinity detection.