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 Psync field indicates beginning of the frame to the ONUs. To break down the bandwidth hurdle of the access over twisted pair cables, it supports high-bandwidth transmission.

GEM | GPON Encapsulation Method | Glossary

GEM provides a connection-oriented, variable-length encapsulayion mechanism for transport of data services over the passive optical network PON. The GEM channels carry variable-length Ethernet frames. Link protection is also known as link aggregationwhich can protect the link and the same time, it can aggregate the traffic as well.

This identifier is assigned by OLT upon creation of a new channel and is only valid during the entire life-cycle of the channel. GEM can fragment its payload. GEM Frame Header detail. A scheduler is used to transmit frames to the U interface. The ODN optical splitters divide the single fiber into multiple fibers going to different buildings and individual homes.

Each bandwidth type has its own QoS feature. Each upstream frame contains a number of transmission bursts coming from one or more ONUs.


Each GEM port bears one kind of service traffic i. The traffic bearing entities within the ONU are granted upstream transmission opportunity encapsuoation bandwidth allocation by the OLT.

Figure 4 shows a detailed downstream GTS frame format.

Each GEM port bears one kind of service traffic i. How to select a right optical fiber? Figure 1 shows various FTTx network architectures. This T-CONT is of best-effort type and mainly used for data services such as Internet and services of low encalsulation which do not require high bandwidth.

PON system may be symmetrical or asymmetrical. The grant map is dynamically re-calculated every few milliseconds. 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 and priority bits.

The CRC field provides error detection and correction on bandwidth allocation field. The downstream transmission, i. One of the basic requirements of an optical system is to provide components with sufficient capacity to extend the optical signal to the expected range. The next section describes GPON key technologies. The physical layer overhead PLOu at the start of the ONU upstream gpoj contains the preamble which ensures proper physical layer operation of the burst-mode upstream link.

GPON: VLANs and GEM Ports – Knowledge Base

Because the access network is shared, ONU upstream transmissions could collide if they were transmitted at random times. It appears as a single ypon for the purpose of upstream bandwidth assignment on the PON. GPON supports triple-play services, high-bandwidth, long reach upto 20kmetc. At the ONT, the traffic is classified again and placed into appropriate queues for each U interface. 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.


Gpoj Slot Start and Stop field indicates the beginning and ending of upstream transmission window.

The splitters are designated as [n: 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 Encapzulation map dictates the arrangement of the bursts within the frame and the allocation intervals within each burst.

Key Technologies of GPON:GEM

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. Both T-CONT are of guaranteed bandwidth types and mainly used for video services and data services of higher priorities. 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 adopts two multiplexing mechanisms- a in downstream direction i.