中文摘要：

介绍了一种基于光纤气泡和纤芯失配的Mach．Zehnder干涉液体折射率传感器．将两根纤芯经过腐蚀的普通单模光纤熔接在一起，在熔接点处形成一个气泡，在距气泡20mm处级联一段20rflrll的细芯光纤，再接入一段单模光纤，形成单模光纤一气泡一单模光纤。细芯光纤．单模光纤结构的传感器．气泡与光纤芯径失配处的两个节点起到光纤耦合器的作用，从而形成光纤Mach．Zehnder干涉仪．环境液体折射率的变化，将使得传感器透射谱能量发生变化，通过测量干涉谱波峰峰值能量从而实现对折射率的测量．并对所制作传感器的折射率响应特性进行了实验研究，实验结果表明干涉谱波峰峰值能量与环境液体折射率之间存在良好的线性关系，当环境液体折射率变化范围在1．35l一1．402时，响应灵敏度为143．537dB／RIU，线性度0．996．该传感器在生物化学领域有较好的应用前景．

英文摘要：

A kind of optical fiber liquid refractive index sensor is proposed based on fiber core etched air-bubble and core diameter mis- matched in-fiber Mach-Zehnder interferometer. A core etched standard single-mode fiber is spliced to another core etched standard single-mode fiber （SMF） to form an air bubble at the connecting point, and a 20 mm thinned fiber is cascaded （TCF） by fusion splicing method, which is 20 mm apart from the bubble, then a leading-mode fiber is spliced to the thinned fiber to form a structure of SMF- （air-bubble）-SMF-TCF-SMF in-fiber Mach-Zehnder interferometer liquid refractive index sensor. The air-bubble and the two fiber core diameter mismatched points serve as optical couplers for modes conversion. The transmission spectrum of sensor is studied by experiment. Results shows that the peak power changes with respect to surrounding refractive index with good linearity. The sensitivity of the sensor is 142.537 dB/RIU in the range of 1.351--1.402 with linearity of 0.996, making it a good candidate for bio-chemical measurements.