What’s the Difference Between GPON and EPON

What’s the Difference between GPON and
EPON?
GPON provides an efficient means of transmission for Ethernet and TDM. As for the
lowest cost business, the need for a Layer 2 protocol is Ethernet. Why not choose
EPON? We will discuss the differences between GPON and EPON in the following
and it is these differences that make GPON become technology choices to the large
operators’ deployment.
A good starting point for discussion of GPON and EPON on access network is
making a brief review toward their mission statement sponsored by agencies. Based
on the following observations, IEEE promotes EFM Study Group to realize the
Ethernet as an access technology:
1. Supports users to access to the network topology: point to multipoint fiber
transmission; point to point fiber transmission; point to point copper transmission.
2. Offers a range of physical layer specifications:
1000BASE-X Extended temperature range of optical components;
1000BASE-X≥10km, a single-mode fiber (SM fiber);
PON physical layer, ≥10km, 1000Mbps, single-mode fiber, ≥1: 16;
Single voice grade copper for no load on the physical layer.
3. Distance ≥2500ft, speed ≥10Mbps; support user access to the remote network
OAM; remote fault indication; remote loopback; link status monitoring.
EPON lack of flexibility GPON with flexibility
Line Speed Fixed 1.25Gbps in both
directions
 Variable and up to
2.5Gbps
 Can be chosen between
performance and the cost
of optical devices
Optical Network  10km, 20km
 With A and B grade
 20km, 60km
 With A, B and C grade:
further or higher split
ratio
Split ratio 1:16 1:64; 1:128
Efficiency 51% when it reaches to 1Gbps 92% when it reaches to 1 or
2Gbps
Successor of BPON No  Full use of the BPON
investment
 Operators can migrate
1

between the same ODN
rules
From rural to urban, GPON is widely used in telecom density and urbanization range,
the higher line speed and efficiency, and the split ratio of it, the higher flexibility it
provides. The optical budget of GPON is more suitable for common long-range loop
in North American. The selection of GPON line speed makes it optimized for
performance and cost. The cos
The higher GPON line speed will support more services or achieve more surplus
income. Moreover, the support to the TDM over GEM has provided a safe alternative
for the transmission of traditional business TDM over GEM to provide.
GPON only standardized to the line OA&M. In most cases the management of ONT
and the service provided by ONT is usually supported by SNMP, thus generating the
problem of management and interoperability. In addition, as the object being managed
is not in accordance with the needs of the service provider, so, ONT often lack of
some key O&M features such as line testing and other fault isolation tools.
There is no inherent security measures to EPON: no encryption on link layer. Since
the ONT can deceive downlink LAN address and communication, security is further
decreased. These risks can be bypassed by adding encryption on some EPON transfer
layer, but this will complicate the network or application, and when the application
must be taken in different ways with the end position different, it will run a timer as a
unified Ethernet protocol.
GPON provided protection or redundancy options for access network, and high-end
business services often need such service characteristics. Most importantly, GPON
has a comprehensive support, including interoperability from different vendors
between the OLT and ONT. This greatly reduces the risk of service providers on the
requirements of mixing and matching ONT and OLT, and by making new entrants
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provide a solution for the existing network rapidly, thereby reducing the entrance of
innovation.
The requirements of the light layer between GPON and EPON is different, because
the downlink rate of GPON is 2.5Gbps while the line rate of EPON is only 1.25Gbps.
However, as the link of 2.5G is a pair of continuous link transmitter/receiver, and is
similar with the mass-produced SONET OC-48 (SDH’ STM-16), so there is no extra
cost on it. As for the Uplink rate terms, GPON and EPON nearly the same, and for the
1.2Gbps line rate, the cost of them is the same. EPON may need a little bit extra costs,
since it does not support power classification, that is to say, the operating range of the
receiver in a burst mode on EPON will be more than GPON. Although the cost of
GPON and EPON transmitter/receiver is the same, the GPON will have advantages
on the budget of optical link +3 dB compared with EPON. And the 3dB may extend
10km of the fiber distance, or support twice number of GPON ONT on the same
GPON OLT, greatly reduced the equipment costs of CO.
According to different line coding and cost, we get the following benefits of each
technology bandwidth
Downstream
rate (Mbps)
Upstream
rate (Mbps)
Downstream
efficiency
Downstream
practical
bandwidth
(Mbps)
Split ratio
EPON 1250 1250 72% 900 1:32
GPON 2500 1250 92% 2300 1:64
Example:
Different bandwidth gains will affect the split ratio allowed by each technology in
different ways, and be subject to different OLT port number/the average throughput.
Now we will set an example to let you know clearly about the comparison between
EPON and GPON. Assuming the existence of a FTTH network has 10,000 service
users. Neither speculate the type of service (Internet access, VOIP, using MPEG-2 or
-4 standardized IPTV, as well as SDTV or HDTV), nor speculate the number of
services per household, we just consider the average throughput of Ethernet-based
services into the home. Due to the technology cost roughly the same, we can also
assume the equipment cost roughly the same, so we can make the following
assumptions:
Average
throughput
(Mbps)
10 20 30 40 50 60 70 80 90 100
Number of 313 313 334 455 556 667 834 910 1000 1112
3

EPON
OLT
Number of
GPON
OLT
157 157 157 176 218 264 313 358 400 435
GPON
OLT:
EPON
OLT
1:2 1:2 1:2.2 1:2.6 1:2.6 1:2.6 1:2.7 1:2.6 1:2.5 1:2.6
Now we can use the result to calculate the average cost/user of each technology
according to average throughput.
The significant cost advantage of GPON is the decrease of the required OLT numbers.
That is to say, GPON adoption will be cheaper compared with EPON solutions, and
moreover, it will help operators to bring other cost savings, such as space, but the
most important is power consumption and heat dissipation.
More related:
What is GPON
Huawei ONT Models for Oversea Carrier
How to Configure the Logical Distance of GPON
GPON – Gigabit Passive Optical Network Introduction
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