traffic by using GPON encapsulating method. (GEM). 2. GPON fundamentals. Active transmission equipment in GPON network consists only of Optical Line. FTTH GPON – Learn FTTH in simple and easy steps starting from basic to advanced GEM (GPON Encapsulation Method) supports both native TDM and Data. EPON and GPON are popular versions of passive optical networks (PONs) GPON also uses a generic encapsulation method to carry other.

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A traffic bearing object within an ONT that represents a group of logical connections, and is treated as a single entity for the mehtod of upstream bandwidth assignment on the PON.

The bandwidth allocations to different Alloc-IDs are multiplexed in time as specified by the OLT in the bandwidth maps transmitted downstream. For example — Video at a different wavelength. Type 2 and Type 3: It is allocated by OLT i.

The grant map is dynamically re-calculated every emcapsulation milliseconds. There are 2 types of GEM Channels: There are three categories or classes of components, which are based on power and sensitivity. It is then transmitted in the downstream direction to the PON interface by using a scheduler.

ONU management encapsulatiin control The Psync field indicates beginning of the frame to the ONUs. The CRC field provides error detection and correction on bandwidth allocation field. The downstream frame has a duration of microseconds and is bytes long, which corresponds to the downstream data rate of 2.

Figure 5 shows upstream GTC frame format. From the Optical Splitter, a single mode SM fibre strand run to each user. GPON adopts two multiplexing mechanisms- a in downstream direction i. The number of entries is given in the Plend field. Methid is the data transport scheme in the specified GPON transmission convergence layer. Figure encaapsulation shows the GTC frame structures for downstream and upstream directions. To break down the bandwidth hurdle of the access over twisted pair cables, it supports high-bandwidth transmission.


The splitters are designated as [n: In case, any one fiber out of these two fibers is cut the ONU can be accessed through other fiber. The Port ID ranges from 0 to In the upstream direction, it is used to bear the service traffic. The Ident field contains an 8-KHz Superframe Counter field which is employed by the encryption system, and may also be used to provide low rate synchronous reference signals. GPON supports triple-play services, high-bandwidth, long reach upto 20kmetc.

The BW map dictates the arrangement of the bursts within the frame and the allocation intervals within each burst. The downstream GTC frame provides the common time reference for enccapsulation PON and common control signaling for the upstream. It is a recipient of upstream bandwidth allocations within the ONU.

GEM | GPON Encapsulation Method | Glossary

The Port ID ranges from 0 to Subscriber 3 in Figure 3 In the downstream direction, the OLT removes the outer tag or passes through the traffic to proper GEM port based on the tag value encalsulation priority bits. There are 2 variations on tag assignment at V interface encapsulztion upstream direction – the traffic at V interface could be double-tagged or single-tagged.

Each upstream frame contains a number of transmission bursts coming from one or more ONUs. Both T-CONT are of guaranteed bandwidth types and mainly used for video services and data services of higher priorities.

Key Technologies of GPON:GEM | FTTH & Triple Play Broadband equipment

The downstream GTC frame provides the common time reference for the PON and the common control signaling for the upstream. Link protection is also known as link aggregationwhich can protect the link and the same time, it can aggregate the traffic as well. This is shown in figure 2. GFP allows direct encapsulation of variable length packets without repeating the encapsulation overhead on a regular basis. Figure 4 shows a detailed downstream GTS frame format.

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It is allocated by OLT i.

GEM provides a connection-oriented, variable-length framing mechanism for transport of data services over the passive optical network PON. The traffic bearing entities within the ,ethod are granted upstream transmission opportunity or bandwidth allocation by the OLT. The optical network terminal ONTwhich is connected to the OLT at uplink side for service network interface, has many user-network interface ports.

A grant is permission to use a defined interval of time for upstream transmission. The upstream GTS frame contains multiple transmission bursts. GEM supports fragmentation and reassembly.

Email will not be published required. GEM Frame Header detail. Figure 1 shows glon FTTx network architectures. Gpoh appears as a single entity for the purpose of upstream bandwidth assignment on the PON. Each bandwidth type has its own QoS feature. The V reference point represents the network-facing interface of the OLT. Each Ethernet is mapped to a single or multiple by fragmenting GEM frames. If the ONU has no traffic to send, it transmits idle frames.


PON Core shell consists of two parts. At the ONT, the traffic is classified again and placed into appropriate queues for each U interface. The parity bit is set to provide an even number of 1s within the header.