Research Of Digital Access System Of Fiber Bragg Grating Sensing Signal Based On GPON

To realize remote transmission of optical fiber grating sensing signal easily, thispaper puts forward a scheme that is transmitting wired optical fiber grating sensing signalby Gigabit Passive Optical network (GPON). The scheme not only saves much moneyand resources which will be spent on laying large-scale special fiber channel but alsoincreases flexibility of forming sensing network. In this scheme, using only onemonitoring center to monitor multiple sensor networks can overcome the disadvantage oflocal monitoring that there is limited monitoring scope. It implements centralizedmonitoring and provides reliable safety guarantee for sensing field.Firstly, sensor network is divided into two kinds: time driven sensing network andevent driven sensing network according to the way of producing sensor data packet.Combined with optical fiber grating sensor network inherent characteristic, this paperseparately chooses fixed length threshold algorithm and double threshold algorithm forthe two kinds of sensor network when sensing subnet forms data frames. Adopting thesealgorithms not only reduces the frame delay of sensing subnet data frame (SSDF) butalso effectively limit the length of data frame. In order to make sensing signal accessGPON network in digitalization，this paper designs the structure of SSDF and illustratesthe encoding process of sensor packet.Secondly, comparing to various multiplexing way, and the time resource of SSDF isrich relative to GPON uplink frame, time division multiplexing way is selected to accessSSDF. This paper designs the function module of access node and the structure of sensingmultiplexing frame. The design of sensing multiplexing frame reduces the number ofcontrol overhead bit in the payload of GEM frame and saves time for remote monitoringcenter to extract useful sensing information. Considering that GPON can access a varietyof business and have many adaptive ways comprehensively, sensing multiplexing framefinally uses one fast Ethernet (FE) port of optical network units (ONU) to access itselfinto GPON.Finally, the paper analyzes factors that influence the overhead of sensing multiplexing frame, as well as sub-frame multiplexing efficiency when the access nodeaccess multiple SSDF by TDM technology and subnet buffer overflow probability withthe number of access subnet changing.