Sensor System Based On Optical Fiber Wireless Convergence

With the development of Internet technology and the innovation pattern of 2.0,"Internet of things","two network convergence" are put forward.The explosive growth of intelligent business,accompanied by huge amounts of information,the existing communication transmission network meets a huge challenge.Meanwhile,since the high definition multimedia,interactive web applications,remote monitoring network are popularized,there is an exponential growth in network traffic globally.It also makes access networks and optical transmission network in face of severe challenge.Obviously,due to its large bandwidth,strong anti-interference ability and many other characteristics,optical fiber transmission network is widely used currently.But the optical cable network flexibility is poor,which limits the distributed deployment of optical network.ROF(radio over fiber),microwave signal is modulated into the laser in central station(center office)through the optical network transmission to the base station.When optical carrier is arrived at the base station,photoelectric detection equipment receives and demodulates the signal.Subsequently,the signal is transferred by the antennas to the user.Since the optical fibers are used as transmission medium,the complex functions such as signal processing,exchanging control are set in the central station,which brings convenience for centralized control and equipment maintenance;The base station,which can achieve photoelectric 'conversion and power amplifier,is easy to be deployed.Moreover,it also has a simple structure and wide communication coverage.However,optical wireless communication is faced with wireless spectrum shortage,as well as transmission bandwidth limited.It's essential for us to solve the problem of the last one kilometer or even the last 100 meters.Based on this theory,designing an optical wireless sensor fusion system with characteristics of large bandwidth,high security,high stability is very necessary.Based on the ROF technology,PON network technology,multimode optical fiber and extensible ZigBee node of the sensor,optical fiber Bragg grating(FBG)sensor,we designed and implemented a dynamic reconfigurable ROF-PON optical wireless sensor fusion system architecture.ZigBee sensor nodes of terminal wirelessly after gathering information sent to the coordinator node antenna,the antenna side will send the signals to the ONU and the ODN in the form of light.FBG sensors center reflection wavelength is demodulated close near the client,and will upload the signals to the ONU.ONU will send light signal into ODN and couple with ZigBee sensor information into the single fiber optical signal transmission until the OLT side.We choose multimode optical fiber for transmission between OLT and ODN.The stokes and anti-stokes light are reflected back to OLT in optical fiber link.Raman wavelength demodulation module of the system and coordinate ZigBee nodes are located in OLT side.After demodulation and processing,the sensor data are saved in the database server.Web server is connected with database server.By calling the database data and published to the Web page,so that the client can visit the Web server via the Internet to browse the sensor data.In this paper,we mainly do research work in the following three aspects:First,we introduce the wireless sensor technology based on ZigBee,FBG sensing technology,distributed fiber Raman sensing technology and wavelength demodulation principle.Then,the design scheme of multi-service sensing system based on database server and B/S architecture is given.The wireless sensor data and optical fiber sensor data are imported into the ROF-PON sensor network.After the demodulation process,the sensing data is stored in the database.The sensor data is presented on the web side for the user's view based on the B/S architecture.Finally,a dynamic reconfigurable ROF system is proposed to realize the conversion of optical carrier in multi-frequency and modulation formats in all-optical domain.