Fiber to the Home

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Fiber to the Home Using
a PON Infrastructure
Fiber to the Home or FTTH: is a technology that uses optical fiber
directly from the central point to the residential premises. It provides
uninterrupted high-speed internet service [1].
Optical Fiber Method can be deployed in two ways: Active Method and
Passive Method. The current mass FTTH deployment is based on the
passive method. Hence, let’s discuss the Passive Method in detail.
Passive Method: The two typical technologies used in this method are
Ethernet Passive Optical Network (EPON) & Gigabit-capable Passive
Optical Networks (GPON). Refer the following image.
The first (PON) activity was initiated by the FSAN group in the
mid1990s. The initial standard covered 155 Mbps. Later on, the standard
enhanced to cover 622 Mbps. In 2001, the IEEE started the development
of an Ethernet based standard known as EPON. In 2001, the FSAN group
started the development of a gigabit speed standard, i.e., GPON, to be
ratified by the ITU-T [2].
 Very high bit rate digital subscriber loop (VDSL) supports a
maximum bit rate of 55 bps. VDSL2 has better QoS and better
SNR.
 ADSL (asymmetric digital subscriber line) supports a maximum
bit rate of 8Mbps, however ADSL2 can go up to 12Mbps.
 SHDSL stands for symmetric high bit rate digital subscriber line.
The larger the diameter of the telephone, the longer the distance it
could reach. The transmission rate depends on the diameter of the
telephone wire.
 Integrated service digital network (ISDN) is based on circuitswitched network.
 Why FTTH? [2]
Fiber offers a number of advantages over the previous technologies
(Copper). The most important ones are as follows:
 Enormous information carrying capacity
 Easily upgradeable
 Easy to install
 Covers very long distances
 Strong, flexible, and reliable
 Safe and secure
 Immune to electromagnetic interference (EMI)
 Lower cost
 The following table lists the advanced services that can be
provided through FTTH along with their bandwidth.
 Optical Line Termination (OLT) A Central Office (CO) equipment
provides PON with the various network interfaces. One OLT serves
multiple ONTs through PON Downstream transmission, i.e., from
OLT to ONT is usually TDM. Upstream traffic, i.e., from ONT to OLT
is usually TDMA. PON system may be either symmetrical or
asymmetrical
 Optical Network Termination (ONT)/ Optical Network Unit (ONU)
An Optical Network Termination is a Customer Premises
Equipment that provides user interfaces to the customer.
 PON
Passive Optical Network (PON): it is point-to-multipoint
architecture which optical splitter in the link, to send same signal to
multiple end points. it comprises of Optical Line Terminal (OLT),
Optical Network Unit and Passive Optical Splitter.[3]
 PON: Downstream


Broadcasting mode: Downstream data is broadcasted to all ONUs.
But, at the ONU, only the specific packet is processed, and the rest
packets are discarded.
Upstream mode (TDMA mode): 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.
The following illustration shows both the technologies together:
 Types of PON Network[3]
Here are some types of PON that have been used throughout the years:
1) APON
Its full name is asynchronous transfer mode (ATM) passive optical
network. As the original PON system, APON uses ATM technology to
transfer data in packets or cells of a fixed size. In APON, downstream
transmission is a continuous ATM stream at a bit rate of 155 Mbps or 622
Mbps. Upstream transmission is in the form of bursts of ATM cells at 155
Mbps.
2) BPON
BPON, also known as broadband PON, is the improved version of
APON. It adopts wavelength division multiplexing (WDM) for
downstream transmission with the transmission rate up to 622 Mbps. It
also provides multiple broadband services such as ATM, Ethernet access
and video distribution. Today, BPON is more popular than APON.
3) EPON
EPON or Ethernet PON uses the Ethernet packets instead of ATM cells.
Upstream and downstream rates of EPON are able to achieve up to 10
Gbps. It is now widely applied to FTTP or FTTH architecture to serve
multiple users. With the advantages of scalability, simplicity, multicast
convenience and capability of providing full service access, many Asian
areas adopt EPON for their networks.
4) GPON
Gigabit PON is the development of BPON. It supports various
transmission rates with the same protocol. The maximum data rate of
downstream is 2.5 Gbps and upstream is 1.25 Gbps. It is also widely used
for FTTH networks. But compared with EPON, its burst sizes and
physical layer overhead are smaller.
Advantages of PON




Low cost, simple maintenance, flexible extensibility and easy to upgrade. And no
need for power during transmission saves a lot for long-term management.
Using pure media network avoids the interference of lightning and electromagnetism.
Thus PON network is suitable for areas under harsh conditions.
Low occupancy of central office resources, low initial investment and high rate of
return.
As the P2MP network, PON is able to provide a large range of service to plenty of
users.
Conclusion
PON network is for sure an effective solution for multiple network users. EPON and
GPON are the most commonly deployed PON systems at present. Since people have
been seeking for higher bandwidth provisioning, the capability of transmission will be
greatly improved in the near future.
References:
1. D&O Committee FTTH Handbook, Edition 6, 2014.
2. https://www.tutorialspoint.com/ftth/ (accessed date: December 2018)
3. http://www.fiber-optical-networking.com/overview-pon-network.html
(accessed date: December 2018)
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