Study On Applications Of Visible And Infrared LED In Optical Communication And Sensing

With the development of semiconductor technology,LED manufacturing technolo-gy has become increasingly mature and its luminous efficiency has been improved and LED life has become long.Since LED species grew various,LED's spectrum has spread across the whole spectrum that has visible light,infrared light and uv-light and luminous intensity has been greatly improved today.Because LED possesses advantages that traditional light source does not have,such as green,small volume,small heat and so on,it has wider applications in the fields of LED display screen,lighting,visible light,infrared sensing and so on.The paper aims to study visible light communication(VLC)technology and LED infrared sensor technology in testing methane concentration.To cope with the increasingly narrow frequency band resources and the weak privacy of traditional communication,visible light communication technology is developed.On the basis of infrared absorption technology,infrared LED methane detection is a new methane sensor technology in testing methane concentration.The technology has the capability of anti-explosion and resistance to electromagnetic interference.The thesis does some research as the following aspects.The first chapter summarizes international and domestic development process of VLC and infrared LED methane detection.Then research significance and research content are introduced.In chapter 2,basic structure and basic characteristics of the LED are introduced in detail such as voltage-current characteristics,temperature property and so on.Meanwhile,we analyze how to select the white LED and infrared LED.In chapter 3,the design of the visible light communication that contains circuit design,software design optical system and single-frequency test is introduced.Firstly,we adopt filter lens to reduce from the interference of other light.Secondly,accordance with the requirements of voice transmission technology,we design the LED drive circuit,A/D conversion circuit,filter amplifier circuit,power supply circuit,software of Single Chip Microcomputer and so on.Finally,the system feasibility test has been carried on.The fourth chapter introduces the types of methane sensor and the measurement method of methane.The sensor with direct measurement method of methane concentration detection is based on the lambert beer's law.LED drive circuit,PD receiving circuit,data acquisition programming,closed glass chamber,aluminum tube dissipating heat and Lab View data acquisition in the system of methane concentration detection are described,too.And finally the preliminary results of the test are presented.On the basis of similar experimental research experience at home and abroad,the fifth chapter summarizes experience and finds shortfalls.The next planning and design is proposed.At the same time,the research direction is prospected.This paper designs the visible light of voice communication system,which transmission rate can be up to 1 Mbit/s,SNR can be greater than 30 dB,transmission distance can be more than 100 meters.And the paper designs methane gas sensor based on the infrared LED,which has the characters of small volume,simple circuit structure and high-resolution.