Study On Chemical Sensors Based On Suspended Core Optical Fiber

Optical fiber is a kind of linear material using total internal reflection to transmit light.In recent decades,optical fiber applications in the sensor field are developing rapidly.The optical fiber sensor has many advantages relative to traditional sensor.Optical fiber can be easily compatible with various types of sensing head,and can be used to measure multi-physical quantity;optical fiber sensor has a large bandwidth,dynamic range and high sensitivity;emergent light from fiber can be easily connected to the photoelectric detector,and translated into electrical signals,matching with computer to realize digital control.This article uses a suspension-core optical fiber with hollow space inside to design and make the chemical sensors.First,corrode the cladding with hydrofluoric acid.Second,choose the middle section as sensing area and bend it into a U shape.Third,connect suspension-core fiber ends with transmitting energy fiber and use fiber fusion splicer to fuse two points which are 1cm from the ends of fiber for blocking the cavity.Fourth,cut two openings on each side 3 cm from the end.Injecting sample solution into suspension-core fiber with micro-flow injection,the evanescent waves on the surface of the core will interact with surrounding solution,which lead to changes of output light intensity.The experiments researched the concentration sensor and fluorescent pH sensor based on suspension-core optical fiber.For concentration sensor,when choosing the methylene blue solution with low concentration,the linearity of the curve of absorbance and concentration is acceptable,verifying the feasibility of the solution concentration sensor.For pH sensors,the fluorescein solution with the same concentration but different pH value(from acidic to alkaline)was injected into suspension-core fiber.The fluorescence spectrum had an obvious degree of differentiation and quick response,so that verified the feasibility of the fluorescence pH sensor.