Research On Multilayer Micro-Mirror Optical Fiber Hydrogen Sensor

Hydrogen is a new type of clean energy which is widely used in industrial field. It shows promising application in aerospace and chemical industries. It has a large storage capacity in nature. In addition, it has no pollution and it is very clean to the environment. But, it’s easy to cause safety accidents. A gas leak could cause a major fire or explosion if it grew dense enough and was ignited by a spark. So people want to detect the leakage of hydrogen with some kinds of sensors and minimize security risks by the detection.Optical fiber hydrogen sensor is a kind of excellent performance equipment in hydrogen detection field. Optical fiber has a good record of electromagnetic interference and it does not generate the static electricity in the course of using. It has much better optical properties than other sensor systems. Micro-mirror optical fiber hydrogen sensor is a kind of optical fiber hydrogen sensors which has some great characteristics such as easy realization and simple structure. It is also a kind of hydrogen sensor with high sensitivity. It has a simple principle with the change of reflectivity with different concentrations of hydrogen.Here how it works:the optical fiber end face is coated with a layer of hydrogen sensitive film. Its reflectivity will be changed when the hydrogen sensitive film contacts with a certain concentration of hydrogen.The change of reflectivity will cause reflected power changes in the optical. The concentration of hydrogen could be detected with the reflected power changes. The research is based on the principle of micro-mirror optical fiber hydrogen sensor.First, the skin-effect of the electromagnetic wave which spreads inside the metal conductor is be studied. The results show that, the electromagnetic wave could pass through the conductor if the film thickness is too thin.The mathematical model is established in order to study the reflection effect of the electromagnetic wave on the surface of the conductor. Palladium based fiber optical hydrogen sensor is one of the most promising configurations for hydrogen sensing. Some mathematical models about hydrogen sensing properties which is coated with palladium are established. Through a series of analysis on the reflectivity changes with the change of palladium film thickness, the results show that, the reflectivity changes obviously when the thickness of palladium film is between10—40nm. And the reflectivity changes little when the thickness of palladium film is more than40nm.In addition, some research on the scattering effect is done in this paper. A fiber optical hydrogen sensor system is designed which is based on the scattering effect.It has a simple principle with the change of the scattering effect when the temperature changes. Some simulation analysis and verification on this sensor model are much helpful to do the next step of experiment.Finally, a sensor probe is designed with multilayer Pd-Au films to build a test system for hydrogen detecting. Through a series of tests,the results show that:The measurement range of the sensor is all about0%-16%and the resolution is about0.7%. It has a good linear effect when the concentration of hydrogen is about2%-6%. The response time of it is less than3s. In general, the sensor shows some good characteristics through the test. It can be used to detect the concentration of hydrogen and it can also be used for early warning of hydrogen leakage.