Huawei ONT, OLT and MDU in GPON technology Leading Huawei networking products distributor-Huanetwork.com

1. Gigabit Passive Optical Network
A longer transmission reach, higher bandwidth, reliability, and lower operating
expense (OPEX) on services.
 Longer transmission distance
 Higher bandwidth
 Better user experience on full services
 Higher resource usage with lower costs
What is GPON?
PON is a point to multi-point (P2MP) passive optical network, GPON stands for
Gigabit Passive Optical Networks. GPON is defined by ITU-T Recommendation
G.984.x. GPON can transport not only Ethernet, but also ATM and TDM (PSTN,
ISDN, E1 and E3) traffic. GPON network consists of mainly two active transmission
equipments, namely- Optical Line Termination (OLT) and Optical Network Unit
(ONU) or Optical Network Termination (ONT). GPON supports triple-play services,
high-bandwidth, long reach (up to 20km), etc.
Figure 1 shows a GPON network.
IFgpon: GPON Interface
SNI: Service Node Interface
UNI: User to Network Interface
CPE: Customer Premises Equipment
The optical line terminal (OLT) is an aggregation device located at the central office
(CO) for terminating the PON protocol. Optical network units (ONUs)/Optical
network terminal (ONTs) are located on the user side, providing various ports for
connecting to user terminals. The OLT and ONUs are connected using an optical
distribution network (ODN) for communication.
The ODN is composed of passive optical components (POS), such as optical fibers,
and one or more passive optical splitters. The ODN provides optical channels between
the OLT and ONUs. It interconnects the OLT and ONUs and is highly reliable. The
ODN network is passive, indicating that no optical amplifier or regenerator is
deployed on the ODN network, thereby reducing maintenance costs of outdoor

2. devices.
GPON History
Starting in 1995, work on fiber to the home architectures was done by the Full Service
Access Network (FSAN) working group, formed by major telecommunications
service providers and system vendors. The International Telecommunications Union
(ITU) did further work, and standardized on two generations of PON. The older ITU-
T G.983 standard was based on Asynchronous Transfer Mode (ATM), and has
therefore been referred to as APON (ATM PON). Further improvements to the
original APON standard–as well as the gradual falling out of favor of ATM as a
protocol–led to the full, final version of ITU-T G.983 being referred to more often as
broadband PON, or BPON. A typical APON/BPON provides 622 megabits per second
(Mbit/s) (OC-12) of downstream bandwidth and 155 Mbit/s (OC-3) of upstream
traffic, although the standard accommodates higher rates.
The ITU-T G.984 Gigabit-capable Passive Optical Networks (GPON) standard
represented an increase, compared to BPON, in both the total bandwidth and
bandwidth efficiency through the use of larger, variable-length packets. Again, the
standards permit several choices of bit rate, but the industry has converged on 2.488
gigabits per second (Gbit/s) of downstream bandwidth, and 1.244 Gbit/s of upstream
bandwidth. GPON Encapsulation Method (GEM) allows very efficient packaging of
user traffic with frame segmentation.
By mid-2008, Verizon had installed over 800,000 lines. British Telecom, BSNL,
Saudi Telecom Company, Etisalat, and AT&T were in advanced trials in Britain, India,
Saudi Arabia, the UAE, and the USA, respectively. GPON networks have now been
deployed in numerous networks across the globe, and the trends indicate higher
growth in GPON than other PON technologies like EPON. According to Huanetwork
estimation, 2014 global OLT ports shipment is 5.8 million, 2014 global ONT unit
shipment is 48.5 million.

3. Why is GPON Required?
As the wide use of broadband services and fiber-in and copper-out development, ISP
(Internet Service Provider) requires a longer transmission reach, higher bandwidth,
reliability, and lower operating expense (OPEX) on services. GPON supports the
following functions to meet these requirements:
Longer transmission distance: The transmission media of optical fibers covers up to
60 km coverage radius on the access layer, resolving transmission distance and
bandwidth issues in twisted pair transmission.
Higher bandwidth: Each GPON port can support a maximum transmission rate of

4. 2.5 Gbit/s in the downstream direction and 1.25 Gbit/s in the upstream direction,
meeting the usage requirements of high-bandwidth services, such as high definition
television (HDTV) and outside broadcast (OB).
Better user experience on full services: Flexible QoS measures support traffic
control based on users and user services, implementing differentiated service
provisioning for different users.
Higher resource usage with lower costs: GPON supports a split ratio up to 1:128. A
feeder fiber from the CO equipment room can be split to up to 128 drop fibers. This
economizes on fiber resources and O&M costs.
GPON System Overview
Introduction to the GPON System
Mainstream PON technologies include Broadband passive optical network (BPON),
Ethernet passive optical network (EPON), and Gigabit passive optical network
(GPON). Adopting the ATM encapsulation mode, BPON is mainly used for carrying
ATM services. With the obsolescence of the ATM technology, BPON also drops out.
EPON is an Ethernet passive optical network technology. GPON is a gigabit passive
optical network technology and is to date the most widely used mainstream optical
access technology.
Figure 4 shows the working principle of the GPON network.
 In the GPON network, the OLT is connected to the optical splitter through a
single optical fiber, and the optical splitter is then connected to ONUs. Different
wavelengths are adopted in the upstream and downstream directions for
transmitting data. Specifically, wavelengths range from 1260 nm to 1360 nm in
the upstream direction and from 1480 nm to 1500 nm in the downstream
direction.
 The GPON adopts WDM to transmit data of different upstream/downstream
wavelengths over the same ODN. Data is broadcast in the downstream direction
and transmitted in the TDMA mode (based on timeslots) in the upstream
direction.
Figure 5 Downstream communication principle of GPON

5. GPON Downstream Transmission
All data is broadcast to all ONUs from the OLT. The ONUs then select and receive
their respective data and discard the other data. Figure 5 shows the details.
Main features:
 Supports point-to-multipoint (P2MP) multicast transmission.
 Broadcasts the same data to all ONUs and differentiates ONU data by GEM port
ID.
 Allows an ONU to receive the desired data by ONU ID.
Figure 6 Upstream communication principle of GPON
GPON Upstream Transmission
In the upstream direction, each ONU can send data to the OLT only in the timeslot
permitted and allocated by the OLT. This ensures that each ONU sends data in a given
sequence, avoiding upstream data conflicts. Figure 6 shows the details.
Main features:
 Supports time division multiple access (TDMA).
 Transits data on an exclusive timeslot.
 Couples optical signals on an optical splitter.
 Detects and prevents collisions through ranging.
GPON Basic Concepts

6. GEM Frame
In the gigabit-capable passive optical network (GPON) system, a GPON
encapsulation mode (GEM) frame is the smallest service-carrying unit and the basic
encapsulation structure. All service streams are encapsulated into the GEM frame and
transmitted over GPON lines. The service streams are identified by GEM ports and
each GEM port is identified by a unique port ID. The port ID is globally allocated by
the OLT. Therefore, the ONUs connected to the same OLT cannot use GEM ports that
have the same port ID. A GEM port is used to identify the virtual service channel that
carries the service stream between the OLT and the ONU. It is similar to the virtual
path identifier (VPI)/virtual channel identifier (VCI) of the asynchronous transfer
mode (ATM) virtual connection. Figure 2 shows the GEM frame structure.
Figure 2 GEM frame structure
A GEM header consists of PLI, Port ID, PTI, and header error check (HEC) and is
used for differentiating data of different GEM ports.
 PLI: indicates the length of data payload.
 Port ID: uniquely identifies a GEM port.
 PTI: indicates the payload type. It is used for identifying the status and type of
data that is being transmitted, for example, whether the operation, administration
and maintenance (OAM) message is being transmitted and whether data
transmission is complete.
 HEC: ensures the forward error correction (FEC) function and transmission
quality.
 Fragment payload: indicates the frame fragment.
The following section describes the GEM frame structure based on the mapping of the
Ethernet service in GPON mode, as shown in Figure 3.
Figure 3 GEM frame structure

7.  The GPON system parses Ethernet frames and maps data into GEM payloads for
transmission.
 Header information is automatically encapsulated into GEM frames.
 The mapping format is clear and has good compatibility.
T-CONT
Transmission container (T-CONT) is a service carrier in the upstream direction in the
GPON system. All GEM ports are mapped to T-CONTs. Then service streams are
transmitted upstream by means of OLT's dynamic bandwidth allocation (DBA)
scheduling. T-CONT is the basic control unit of the upstream service stream in the
GPON system. Each T-CONT is identified by Alloc-ID. The Alloc-ID is allocated by
the GPON port of the OLT, and the T-CONTs used by ONUs connected to the same
GPON port of OLT cannot have the same Alloc-IDs.
There are five types of T-CONT. T-CONT selection varies during the scheduling of
different types of upstream service streams. Each T-CONT bandwidth type has its
own quality of service (QoS) feature. QoS is mainly represented by the bandwidth
guarantee, which can be classified into fixed, assured, non-assured, best-effort, and
hybrid modes (corresponding to type 1 to type 5 listed in Table 1).
Table 1 T-CONT types
Bandwidth
Type
T-CONT Type
Type 1 Type 12 Type 3 Type 4 Type 5
Fixed
Bandwidth
X No No No X
Assured
Bandwidth
No Y Y No Y
Maximum
Bandwidth
Z = X Z = X Z = X Z Z ≥ X + Y
Description The fixed
bandwidth is
reserved for
specific
ONUs or
The assured
bandwidth is
available at any
time required by an
ONU. When the
This type is the
combination of
the assured
bandwidth and
maximum
This type is
the maximum
bandwidth
that can be
used by an
This type is the
combination of the
fixed, assured, and
maximum
bandwidth. It

8. specific
services on
ONUs. It
cannot be
used by other
ONUs even
if no
upstream
service
streams are
carried on the
specific
ONUs.
It applies to
services that
are sensitive
to service
quality. The
services can
be TDM or
VoIP
services.
bandwidth required
by the service
streams on the
ONU is smaller
than the assured
bandwidth, the
system can use the
DBA mechanism to
allocate the
remaining
bandwidth to
services on other
ONUs.
Because DBA is
required, this type
provides a less
real-time
performance
compared with the
fixed bandwidth.
bandwidth. The
system assures
some
bandwidth for
subscribers and
allows
subscribers to
preempt
bandwidth.
However, the
total used
bandwidth
cannot exceed
the maximum
configured
bandwidth.
It applies to
VoIP services.
ONU, fully
providing the
bandwidth
required by
the ONU.
It applies to
IPTV and
other high-
speed Internet
services.
supports the
following functions:
Reserves bandwidth
for subscribers and
the bandwidth
cannot be preempted
by other subscribers.
Provides the
bandwidth to an
ONU at any time
when required
Allow subscribers to
preempt some
bandwidth. (The
total used bandwidth
cannot exceed the
maximum
configured
bandwidth.)
NOTE:
In Table 1, X indicates the fixed bandwidth value, Y indicates the assured bandwidth
value, Z indicates the maximum bandwidth value, and No indicates not involved.
GPON Networking Application
GPON is a passive optical transmission technology that applies in FTTx solutions,
including fiber to the building (FTTB), fiber to the curb (FTTC), fiber to the door
(FTTD), fiber to the home (FTTH), fiber to the mobile base station (FTTM), fiber to
the office (FTTO), and fiber to the WLAN (FTTW), for voice, data, video, private
line access, and base station access services. Figure 7 shows FTTx networking
applications.
Figure 7 FTTx networking applications

9. The FTTx network applications in GPON access have the following in common: The
data, voice, and video signals of terminal users are sent to ONUs, where the signals
are converted into Ethernet packets and then transmitted over optical fibers to the
OLT using the GPON uplink ports on the ONUs. Then, the Ethernet packets are
forwarded to the upper-layer IP network using the uplink port on the OLT.
FTTB/FTTC: The OLT is connected to ONUs in corridors (FTTB) or by the curb
(FTTC) using an optical distribution network (ODN). The ONUs are then connected
to user terminals using xDSL. FTTB/FTTC is applicable to densely-populated
residential communities or office buildings. In this scenario, FTTB/FTTC provides
services of certain bandwidth for common users.
FTTH: The OLT connects to ONTs at user homes using an ODN network. FTTH is
applicable to new apartments or villas in loose distribution. In this scenario, FTTH
provides services of higher bandwidth for high-end users.
FTTO: The OLT is connected to enterprise ONUs using an ODN network. The ONUs
are connected to user terminals using FE, POTS, or Wi-Fi. QinQ VLAN
encapsulation is implemented on the ONUs and the OLT. In this way, transparent and

10. secure data channels can be set up between the enterprise private networks located at
different places, and therefore the service data and BPDUs between the enterprise
private networks can be transparently transmitted over the public network. FTTO is
applicable to enterprise networks. In this scenario, FTTO implements TDM PBX, IP
PBX, and private line service in the enterprise intranets.
FTTD: uses existing access media at user homes to resolve drop fiber issues in FTTH
scenarios.
FTTM: The OLT is connected to ONUs using an ODN network. The ONUs are then
connected to wireless base stations using E1. The OLT connects wireless base stations
to the core IP bearer network using optical access technologies. This implementation
mode is not only simpler than traditional SDH/ATM private line technologies, but
also drives down the costs of base station backhaul. FTTM is applicable to
reconstruction and capacity expansion of mobile bearer networks. In this scenario,
FTTM converges the fixed network and the mobile network on the bearer plane.
FTTW: The OLT connects to ONUs using an ODN network, the ONUs connect to
access points (APs) using GE for WLAN traffic backhaul. FTTW is the trend in Wi-Fi
construction.
GPON Solution Provider Huanetwork
Huanetwork is a independent GPON solution provider, working with over 500 ISPs
and carriers in the world. Huanetwork provides Huawei OLT at very competitive
price, Huawei is the world leader in GPON market with 36% marketshare. Full
GPON solution (OLT, ODN, ONU) include technical support service are all available
at Huanetwork, many ISPs starts their GPON journey by telnet accessing Huanetwork
GPON LAB remotely, which is a free service provided by Huanetwork aiming at
bridging the digital divide.
Interested in GPON solution price, contact sales@huanetwork.com
Interested in Huanetwork LAB test, contact support@huanetwork.com
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