Study On Fluid Sensors Based On Hollow Suspended Core Optical Fiber

Optical fibers have a small mass,light weight,anti-electromagnetic interference,etc,so they have been widely used to manufacture various devices,optical fiber sensors are the main applications of the fiber.With the study of the optical fiber sensors,many types of optical fiber sensor have been developed to measure various parameters,and have been commonly used in industry,agriculture,aerospace and other fields.Due to the characteristics of the optical fiber,the optical fiber sensor is provided with a wide measurement range,high sensitivity,low cost and other features,optical fiber sensor have attracted widespread attention.This paper designs and fabricates two kinds of fiber fluid sensors by the hollow suspended core optical fiber(HSCOF): humidity sensor based the HSCOF and nitrite concentration sensor based the HSCOF.Etching micro pores on the fiber surface,so that the sample can flows into and out of the fiber,and forms microfluidic to realize the measurement of the small sample.The hollow structure of the fiber is used as the measuring cell,the use of the interaction between the evanescent wave of the fiber core and the sample achieves the sensing purposes.The humidity sensor is fabricated by growing the ZnO nanorods in the inner surface of the fiber,the main sensing principle are evanescent wave of the fiber and nanorods provided with the feature of large surface-area-to-volume ratio.Growth of well-arrayed ZnO nanorods in the interior of HSCOF by the method of microfluidic injection,and nanorods contain oxygen and zinc,so the substance proved to be zinc oxide nanorods.Experimental results show that the light intensity is inversely proportional to the relative humidity and good linearity.When the relative humidity alternates from 10% to 40%,the output intensity at 722 nm along alternates,when the relative humidity increased from 10% to when 40%,the response time of the sensor is about 5.5 s,when the relative humidity dropped from 40% to10%,the response time is about 6.5 s.By comparing with untreated fiber,the growth of nanorods sensor is proved more sensitive.Nitrite concentration sensor of principle is the degree of the fluorescence quenching in the fiber,Comsol Multiphysics is used to simulate fluid flow rate and pressure in the fiber,simulation results demonstrate that the flow rate of the fluid and the pressure is smooth distribution inside the fiber,and the flow rate range from 70 mm/s to 10 mm /s between the center and the core of the fiber,so the response time of the sensor is about 5 s.Experimental results illustrate that with the increase of the nitrite concentration,the fluorescence intensity of the output decreases,when the concentration of nitrite solution range from 0.1 mmol/L to4.14 mmol/L,the fluorescence quenching degree curve of the sensor is nearly linear.