The Research On The Application Of Hollow Fiber In Liquid And Gas Sensing

As the demand of the modern industry, various sensing technologies have aroused. The sensing technologies of liquid and air are applied most widely among them. The former is used in chemical industry, health, environmental protection, transportation security monitoring fields, etc. The latter is applied to detect the components of poisonous and harmful gases, air pollutants with a specific application: gas leakage monitoring field, etc. With the development of the optical sensor technology in recent decades, the scope of its application has become more widely progressively. Such as using the principle of SPR to detect liquid and using infrared spectrum sensing technology for different gas detection, etc. Optical sensing technology has many obvious advantages, such as high sensitivity, fast speed and nondestructive testing.Hollow fiber has become a widely used optical transmission waveguide. It has many advantages, such as low section loss, large power threshold, very good flexibility, and good transmission characteristics in infrared wavelength. It also has a very important feature---hollow, this article make full use of it. In the liquid and gas detection, this article uses it as a waveguide and absorption cavity respectively.In liquid detection, a new kind of hollow optical fiber sensor based on surface plasmon resonance is designed. The performance of the designed sensor is theoretically analyzed with a ray model theory. The influences of different configurations of the sensor are also analyzed. It is shown that this hollow optical fiber SPR sensor is more flexible in use than conventional fiber SPR sensors because it can change sensing probes to fit sensing media with different refractive index.In gas detection, the article use common material CO2 as the detection object, designed a portable CO2 concentration detection device which uses hollow fiber as the gas cell. The device is based on Non-dispersive infrared method, using Ag-coated hollow fiber as the light path and sensing chamber at the same time. Hollow fiber has an obvious advantage-its good flexibility. The length of light path can increase as well as decreasing the volume of the detection system. This article completely introduced the design of light source, sensing chamber, coupler, detector and signal processing circuit of the system. At last, the article analyzes the result and data of the research.This article fully demonstrates the feasibility of using hollow fiber in gas and liquid detection. Also, the article comes to a full set of solutions respectively. Some improved methods are also mentioned.