The Research On Refractive Index And PH Value Sensors Based On Micro-structure Optical Fibers

In recent years, Micro-sturcture Optical Fiber optical fibers (MOFs) sensors havereceived huge attention since the first demonstration of the detection of a refractive indexchange in waveguide configurations. MOFs sensors have many advantages such as simplestructure, small volume, high cost-performance and remote analysis, which could be widelyapplied in biomedical, food testing, environmental testing and biological and chemicalwarfare agent detection. Among these MOFs-based designs, two mechanisms, antiresonantreflecting coupling and surface plasmon resonance (SPR) have attracted immense attentionsdue to their contributions to ultra high sensitivity. However, the sensors are restricted to theindex of fiber material. So the researches in how to enlarge the measurement range ofrefractive index of analyte have great scientific and application significance.We note that the antiresonant reflecting coupling happens when the refractive index ofanalyte is higher than that of the surrounding background material and the SPR sensor isreliable in the measurement of analyte with refractive index lower than surroundingbackground material. So in this paper, we propose the sensor based on these two detectionmechanisms for achieving a large dynamic index range. After the optimization of structure,an ultra wide dynamic index range of1.25to1.45can be achieved and the maximalsensitivities reach27000nm/RIU.pH of solution is an another important parameter in the field of biology and chemist. Inthis paper, a fiber coupler is coated with a new pH value sensitive gelatin. This gelatin canabsorb light when it will meet the pH value standard buffer solution. The experimental resultindicated that the sensitivity of this fiber optical pH sensor is high. Meanwhile, it has thegood linearity and response speed.