Tag Archives: EPON

EPON vs. GPON—Which Will Be More Popular?

With the development of passive optical networking (PON) technology, two PON standards are striking in FTTH solution area and they are Ethernet passive optical networking (EPON) and ATM (asynchronous transfer mode)-based Gigabit passive optical networking (GPON). During these years, it has become a hot topic that which will be more popular in broadband access and optical telecom applications, EPON or GPON? This article will compare these two technologies from the differences of architecture, bandwidth, efficiency, cost, etc.


The biggest difference between the two technologies shows in architecture. EPON employs a single Layers 2 network that uses IP to carry data, voice, and video. While GPON provides three Layer 2 networks: ATM for voice, Ethernet for data, and proprietary encapsulation for voice.


EPON provides seamless connectivity for any type of IP-based or other “packetised” “communications”. Since Ethernet devices are so popular and easy to get, implementation of EPONs can be highly cost-effective.

In GPON, virtual circuits are provisioned for different kinds of services sent from a central office primarily to business end users. This kind of transport provides high-quality service, but includes significant overhead because virtual circuits should be provisioned for each type of service. GPON equipment requires multiple protocol conversions, segmentation and reassembly (SAR), virtual channel (VC) termination and point-to-point protocol (PPP).


EPON delivers symmetrical bandwidth of 1 Gbit/s. EPON’s Gigabit Ethernet service actually constitutes 1 Gbit/s of bandwidth for data and 250 Mbit/s of bandwidth for encoding. GPON promises 1.25-Gbit/s or 2.5-Gbit/s downstream, and upstream bandwidths scalable from 155 Mbit/s to 2.5 Gbit/s. GPON’s 1.25-Gbit service specifies a usable bandwidth of 1.25 Gbit/s, with no requirement for encoding. Gigabit Ethernet interfaces to the aggregation switch, central office, and metro are currently cost-effective to aggregate 1-Gbit ports for transport. But for 1.25 Gbit, there is no way.


Efficiency has to be considered in both directions of a PON. Each PON protocol introduces its own overhead in either direction. In the downstream direction, protocol overhead could be negligible. In the upstream direction, the total scheduling overhead within EPON is from 90.33 percent to 97.08 percent compared to a GbE point-to-point link. In the downstream direction, EPON efficiency reaches from 97.13 percent to 98.92 percent of the efficiency of a point-to-point 1GbE link, while GPON in GTC Encapsulation Method (GEM) mode can achieve ~ 95 percent efficiency of its usable bandwidth. The downstream EPON data rate can be doubled to 2.5Gbps comparable to GPON.


EPON simplifies the networks and needs no complex and expensive ATM and Sonet elements. Thus it helps lower the costs to subscribers. Now the cost of EPON equipment is about 10 percent of the costs of GPON equipment.


Encryption is part of the ITU standard. EPON uses an AES-based mechanism, which is supported by multiple silicon vendors and deployed in the field. And EPON encryption is both downstream and upstream. However, GPON encryption is downstream only.

Ethernet Features

EPON is an IEEE Ethernet standard and uses Ethernet switches within its silicon, it can natively support all of the 802.1 and 802.3 Ethernet, including VLAN tags, prioritisation, OAM, etc. All Ethernet services can be natively delivered in a manner identical to what is done with switched Ethernet today. As to GPON, it only defines the transport of Ethernet frames. So it has no native Ethernet functionality. Ethernet switches must be placed either in front of or within GPON OLTs and ONTs to provide any additional Ethernet capabilities.

EPON and GPON technologies have been introduced into the market because of service quality and price point. By comparing the differences of the two technologies, it shows EPON is a superior technology for delivering residential and small-to-medium enterprise Ethernet services in terms of its advantages in bandwidth, efficiency, cost, encryption and Ethernet features. So EPON will be employed in FTTH solution area in a large scale earlier and faster than GPON.

Originally published at http://www.streetarticles.com/internet-and-businesses-online/epon-vs-gponwhich-will-be-more-popular

EPON — An Ideal Optical Access Network Solution

In recent years, the telecommunications backbone has experienced huge growth. The tremendous growth of Internet traffic has far surpassed the network capacity. The “last mile” still remains the bottle neck between high-capacity local area networks and the backbone network. So a new technology for optical access network, which is simple, scalable but not expensive, is needed. And that is Ethernet passive optical network (EPON).

EPON Definition

EPON, unlike other PON technologies which are based on the ATM standard, is based on the Ethernet standard. This lets you utilise the economies-of-scale of Ethernet, and provides simple, easy-to-manage connectivity to Ethernet-based, IP equipment, both at the customer premises and at the central office. As with other Gigabit Ethernet media, it is well-suited to carry packetized traffic, which is dominant at the access layer, as well as time-sensitive voice and video traffic.

EPON Network

An EPON network includes two parts: an optical line terminal (OLT) and an optical network unit (ONU).

The OLT resides in the central office (CO). This could typically be an Ethernet switch or Media Converter platform. OLT is mainly designed for controlling the information float across the optical distribution network (ODN). OLT has two float directions: upstream (getting an distributing different type of data and voice traffic from users) and downstream (getting data, voice and video traffic from metro network or from a long-haul network and sending it to all ONU modules on the ODN.

The ONU resides at or near the customer premise, in a building, or on the curb outside. It uses optical fibre for connecting to the PON on the one side, while interfacing with customers on the other side.

EPON Upstream and Downstream Traffic

In an EPON, the process of transmitting data downstream from the OLT to multiple ONU is fundamentally different from transmitting data upstream from multiple ONUs to the OLT.

In the downstream direction (from network to user), Ethernet frames transmitted by OLT pass through a 1:N (N represents the number of subscribers each fibre can serve) passive splitter and reach each ONU. Splitting ratios are usually between 4 and 64. At the splitter, the traffic is divided into separate signals, each carrying all of the ONU–specific packets. When the data reaches the ONU, it accepts the packets that are intended for it and discards the packets that are intended for other ONUs.


In the upstream direction (from user to network ), due to the directional properties of a passive combiner (optical splitter), data frames from any ONU will only reach the OLT, not other ONUs. Frames in EPON from different ONUs transmitted simultaneously may collide. Thus, ONUs need to share the trunk fibre channel capacity and resources.


EPON Advantages

First, EPON uses a point-to-multipoint topology instead of point–to-point in the outside plant. Thus it saves much of the cost of running fibre from every customer to the CO, installing active electronics at both ends of each fibre and managing all of the fibre connections at the CO. And EPON also eliminates active electronic components, such as regenerators and amplifiers, and replaces them with passive optical couplers that are less-expensive, simpler, and longer lived than active ones. As to the cost of expensive electronic components and lasers in the OLT, it will be shared over many subscribers not paid by each subscriber.

Second, EPON offers high bandwidth to subscriber. The traffic rates of 1Gbps in downstream and return traffic of 800 Mbps have been achieved already. Compared with point–to-point technology, EPON is specially made to address the unique demands of the access work. So more bandwidth can be got by each subscriber.

At last, the main advantage of EPON is that it can eliminate complex and expensive asynchronous transfer mode (ATM) and SONET elements and simplify the networks dramatically. Traditional telecom networks use a complex and multilayered architecture. While this architecture requires a router network to carry IP traffic, ATM switches to create virtual circuits, add/drop multiplexers (ADM) and digital cross-connects to manage SONET rings, and point-to-point DWDM optical links.


EPON is suitable for Fibre-to-the-Home/Building/Business applications, including voice, data and video services. EPON is a shared network but with much higher bandwidth. It’s a highly attractive access solution for service providers to extend fibre into the last mile because of low cost and good performance, resulting from their nature as passive networks, point-to-multipoint architecture, and native Ethernet protocol.

A Guide for PON

Nowadays, there is a growing popularity of Video-on-Demand (VoD), VoIP and increased IPTV deployment. Providers aim to offering fibre-to-the-home (FTTH), (fibre-to-the-building) FTTB and fibre-to-the-curb (FTTC) solutions through advancing passive optical network (PON) technology. The term “PON” may confuse you for its complexity and extensiveness. Details are as followed.

PON is a single, shared optical fibre that uses inexpensive optical splitters to divide the single fibre into separate strands. It can build up a point-to-point topology supporting 1Gbps transmission to home and business typically within 20km. PON system is called “passive” because that there are no active electronics within the access network. It uses optical splitters to separate and collect signals rather than electrically powered switching equipment.

PON consists of an Optical Line Terminal (OLT) connected to multiple Optical Network Units (ONUs) via an Optical Distribution Network (ODN).

OLT: it is a device at the service provider’s central office, performing conversion between the electrical signals used by the service provider’s equipment and the fibre optic signals used by the passive optical network and coordinating the multiplexing between the conversion devices on the other end of that network.

ODN: it is used for distributing signals to users in a telecommunications network by optical fibre. ODN has been made up entirely of passive optical components particularly singlemode optical fibres and optical splitters.

ONUs: they are devices near end users, delivering traffic-load information provided by OLTs to each end user.PON System

PON system has achieved significant deployment in today’s FTTx networks especially in FTTH networks as the development of Gigabit passive optical network (GPON) and Ethernet passive optical network (EPON). Nowadays, GPON and EPON are the mostly widely used types of PON for their low cost, high bandwidth, great flexibility and easy management, etc.

GPON: it is defined by ITU-T recommendation series G.984.1 through G.984.6. It can transport not only Ethernet, but also ATM and TDM (PSTN, ISDN, E1 and E3) traffic. It supports services like carrying video and delivering video on single fibre distribution, allowing low-consuming transmission, more efficient maintenance, cabling and overall performance.

EPON: it is defined by the Ethernet standard rather than by the ATM standard, making you utilise the economies-of-scale of Ethernet. It can provide simple and easy-to-manage connectivity to Ethernet-based, IP equipment both at the customer premises and at the central office. It is perfect for voice and video traffic solution as with other Gigabit Ethernet media.GPON and EPON

 For more information about OLTs, Optical Splitters and ONUs, please visit FS.COM.