July 15, 2019
GPON technology introduction
GPON (Gigabit passive optical network) full name is Gigabit-capable PON Gigabit/Gigabit passive optical network, and is also a passive optical network. The GPON service is an extension of BPON. Compared with other PON standards, the GPON standard provides unprecedented high bandwidth (downlink rate of nearly 2.5Gbps), and its asymmetric characteristics are more suitable for the broadband data service market.It provides full service guarantee of QoS, and carries ATM cells and/or GEM frames. It has good service level, QoS guarantee and full service access capability. When carrying GEM frames, TDM services can be mapped. To GEM frames, standard 8 kHz (125 μs) frames can be used to directly support TDM services. As a carrier-grade technical standard, GPON also specifies protection mechanisms and complete OAM functions at the access network level.Its downlink maximum transmission rate can be as high as 2.488Gps, the maximum uplink transmission rate is 1.244Gbps, and the transmission distance can reach 20 to 37 kilometers. Therefore, it has many features such as high bandwidth, high speed, high efficiency transmission, wide coverage, and rich user interface. Therefore, it has been regarded by most operators as an ideal technology for broadband and integrated transformation of access network services..
As a flexible broadband optical access technology proposed by ITU-T, in the GPON standard, it is clearly stated that the types of services that GPON needs to support include data services (Ethernet services, including IP services and MPEG video streams), and PSTN services (POTS, ISDN services), dedicated lines (T1, E1, DS3, E3 and ATM services) and video services (digital video) for multi-user VoIP, multi-video streaming (eg IPTV) and standards using MPEG-2 or -4 specifications Demand for "triple play" such as resolution TV (SDTV) or high definition television (HDTV) and multi-user high-speed Internet access. Moreover, multiple services in the GPON are mapped to ATM cells or GEM frames for transmission, and corresponding QoS guarantees can be provided for various service types.GPON generally adopts a tree topology. When service protection and channel protection are required, a protection ring can be added to provide protection for some optical network terminal ONTs.
It is composed of an optical line terminal OLT (Optical Line Terminal), an optical network terminal ONT (Optical Network Terminal) / ONU (Optical Network Unit), and a ring-shaped (or tree) topology passive optical network PON. The OLT is located in the central office and provides WAN interfaces up to the GbE, OC-3/STM-1, DS-3, etc., and provides 2.488 Gbps optical interfaces to the PON. The ONT/ONU is placed in the user terminal to provide users with application interfaces such as 10/100BaseT, T1/E1, and DS-3. The optical interface rates of the PON are 155 Mbps, 622 Mbps, 1.244 Gbps, and 2.488 Gbps. The direction from the OLT to the ONT/ONU is the downlink direction, and the data transmission mode of the broadcast transmission is adopted; otherwise, the uplink direction is adopted, and the time division multiple access technology based on the statistical multiplexing is adopted. The PON can implement full-duplex transmission of data streams by Coarse Wavelength Division Multiplexing (CWDM) coverage.