The Design Of OLT GTC-layer For GPON System

As the years of development of passive optical network (PON) technology, It is no doubt that PON will become the future development direction in access network. The new business of internet appears one by one. It make people increases the demands of bandwidth of network access. The traditional access method will not be able to effectively meet the future demands of the bandwidth. The fiber access technology with PON technology as the representative Will gradually replace the existing phone line access mode,and become to next-generation access network technology which can provide multi-service access, high bandwidth and QoS guarantee with its high capacity bandwidth and wide coverage areas.FTTX will enter a new era of large-scale commercial.Gigabit-capable Passive Optical Network (GPON) and Ethernet Passive Optical Network (EPON) technology is recognized as the current two kinds main implementation technology of FTTX. GPON is developed by the ITU-T and its rate can up to 2.5 Gbit/s. It is able to transmit data of voice, Ethernet, ATM and other business in their original format. GPON uses the new Transmission Convergence layer technology "Generic Framing Protocol", to achieve the multi-traffic general framer encapsulation, and to provide a general adapt mechanism to high layer user traffic. User signal can be translated on base IP or constant speed. GPON encapsulation mode (GEM) can provide a common, efficient and simple encapsulation method for different business. The frame of GPON using a fixed rate of 125us is able to directly support TDM services.GPON transmission convergence (GTC) is the key innovation point of GPON technology.GPON use GTC frame as the transmission cell between the OLT and ONUs.GTC layer provides control and management function for OLT and ONUs,implement bandwidth allocation and perform multiplexing and demultiplexing of frames. The design of GTC layer play an important role in A stable GPON system,especially for OLT GTC. Therefore, to be able to give full play to the advantages of GPON technology, we should give a high level design of GTC.It is the key to play to the strongpoint of GPON system that how to design an efficient data services according to the characteristics of data.It is also the difficulty of to design the OLT GTC-layer.The paper describes the development of GPON and Contrast GPON technology and EPON technology. It focus on describing the basic principles of GPON, the functions of the OLT GTC and the GTC layer circuit design ideas and algorithm,and proposes a new way to achieve the GEM adaptation, GEM reassembly and GEM transmission which based on the look-up table.