Research And Design Of Internet Of Things System Based On Fiber Optic Sensing

Internet of things(IoT), is a network connected to physical objects. It is usually divided into three layers, the sensing layer, network layer and application layer. At present, the sensing layer mostly consists of electic sensors. In recent years, optical communication technology is developing fastly, and fiber optic sensors gradually come into view. The optical fiber sensors take light as the information carrier, the optical fiber as the transmission medium, which have advantages of both the the transmission fiber and optical measurement. Relative to electric sensors, fiber optic sensors have more advantages, such as anti-electromagnetic interference, corrosion resistance, high temperature resistance, high sensitivity, etc, which enables passive sensing. So fiber optic sensors apply to the monitoring of harsh environments such as insulation, underwater, mines, etc, which is not suitable for insulating electrical sensors working. Also, fiber optic sensors is easy to form networks and realize remote monitoring.In this paper, fiber Bragg grating and distributed feedback fiber laser (DFB-FL) are used as the sensing terminals of the IOT platform. In the former sensor network, optic signal is detected and converted into an electrical signal for further processing by wavelength demodulation module and then the sensing data is transferred into the host computer by USB, so that we can storage the data and achieve long-distance monitoring. In the latter senor network, the electrical signal after photoelectric conversion is collected into DSP, which can achieve digital demodulation, and then the demodulated information is saved into the computer through the network port or serial port. Monitoring data obtained by the two methods is released uniformly via B/S architecture, allowing users to facilitate the realization of remote monitoring the environment of the sensor node in the computer’s browser. The most important feature of the system is achieving the remote monitoring high-frequency and slowly varying quantities in two sensing ways anytime and anywhere, and the sensing layer is passive. The main work and innovation of this paper are as follows: Investigate and survey the Internet of Things architecture and related technologies, the various kinds of optical fiber sensing technologies, optical fiber gratings and wavelength demodulation method commonly used. Analyze the wavelength demodulation technology for sensing based on distributed feedback fiber laser, which is the principle of PGC demodulation method based on the non-equilibrium M-Z fiber optic interferometer.Design a temperature sensing system based on fiber Bragg grating and a vibration signal sensing system based DFB-FL. Present the design scheme of remote-monitoring platform system for the application of Internet of things based on the two sets of fiber optic sensing systems. Use the wavelength demodulation module to demodulate the temperature sensing signal by software in computer. Use the DSPs to achieve the digital simulation of PGC demodulation, and present the design of hardware and software for PGC demodulation system based on DSPs.Finally, the data collected in two ways of sensing is stored in the database of the computer, and realise the real-time monitoring data releasing based on B/S architecture.