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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The Flag field allows the upstream transmission of physical layer overhead blocks for a designated ONU. It is allocated by the OLT, i. Downstream Traffic Management Figure 6 shows a sample model ,ethod downstream traffic management.

Each upstream transmission burst contains an upstream physical layer overhead PLOu section and one or more bandwidth allocation intervals associated with the individual Alloc-IDs.

GPON Fundamentals – Knowledge Base

The parity bit is set to provide an even number of 1s within the header. For example, Un-fragmented Ethernet frame as shown in the following illustration.

The Slot Start and Stop field indicates the beginning and ending of upstream transmission window. However, it avoids large overhead by allowing variable length frames.

For example — Video at a different wavelength. Each Ethernet is mapped to a single or multiple by fragmenting GEM frames. A scheduler is used to transmit frames to the U interface.


The optical network terminal ONTwhich is connected to the OLT at uplink side for service network interface, has many user-network interface ports. The V reference point encapsupation the network-facing interface of the OLT. The downstream frame has a duration of microseconds and is bytes long, which corresponds to the downstream data rate of 2. Each upstream frame contains a number of transmission bursts coming from one or more ONUs.

It is enacpsulation recipient of upstream bandwidth allocations within the ONU. The number of entries is given in the Plend field.

GPON supports triple-play services, high-bandwidth, long reach upto 20kmetc. 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.

This combination of the two; together makes the ONT the most cost effective solution to provide GPON services to local and single-family, small, and medium enterprises. GEM provides a connection-oriented, variable-length framing mechanism for transport of data services over the passive optical network PON.

GPON adopts two multiplexing mechanisms- a in downstream direction i. In case, any one fiber out of these two fibers is cut the ONU can be accessed through other fiber. A traffic bearing object within an ONT that represents a group of logical connections, and is treated as a single entity for the purpose of upstream bandwidth assignment on the PON. The upstream GTS frame contains multiple transmission bursts.

It is allocated by OLT i.

Figure 4 shows a detailed downstream GTS frame format. The ONUs then act upon the relevant information contained therein. A single fibre from the OLT runs to a passive Optical Splitter passive means, it does not require any power to operate which is located near the users’ locations. The BW map dictates the arrangement of the bursts within the frame and the allocation intervals within each burst. Each bandwidth type has its own QoS feature. DBA is a methodology that allows quick adoption of users’ bandwidth allocation based on current traffic requirements and it is especially good for dealing with bursty upstream traffic.


Each GEM port bears one kind of service traffic i. It is then transmitted in the downstream direction to the PON interface by using a scheduler.

Key Technologies of GPON:GEM

The downstream GTC frame provides the common time reference for the PON and common control signaling for the upstream. There are 2 variations on tag assignment at V interface in upstream direction – the traffic at V interface could be double-tagged or single-tagged. Both T-CONT are of guaranteed bandwidth types and mainly used for video services and data services of higher priorities.

The Optical Splitter merely divides the optical power into N separate paths to the users. A grant is permission to use a defined interval of time for upstream transmission.