Emerging Technologies: PON: Wonder Network

A passive optical network (PON) is a point-to-multipoint,
fiber-to-the-premises (FTTP) network architecture in which unpowered optical
splitters are used to enable a single optical fiber to serve multiple premises.
Depending on where the PON terminates, the system can be described as
fiber-to-the-curb (FTTC), fiber-to-the-building (FTTB), or fiber-to-the-home (FTTH).
A PON consists of an optical line termination (OLT) at the service provider's
central office and a number of optical network units (ONUs) near end users.
Typically, up to thirty-two ONUs can be connected to an OLT. Optical
transmission has no power requirements or active electronic parts once the
signal is going through the network. In a stand-alone system, a PON could
deliver up to 622 Mbps downstream and up to 155 Mbps upstream to the user.
Multiple users of a PON could be allocated portions of this bandwidth.

In PON, the process of transporting data downstream to the
customer premises is different from transporting data upstream from the customer
premises. Downstream data is broadcasted from the OLT to each ONT. Each ONT
processes the data by matching the address at the protocol transmission unit
header. There is a need to coordinate between the transmissions of each of the
ONTs to the OLT in order to avoid collisions. Upstream data is transmitted
according to control mechanisms in the OLT, using a TDMA (time division multiple
access) protocol, in which dedicated transmission time slots are granted to each
individual ONT. The time slots are synchronized so that transmission bursts from
different ONTs do not collide.

Current Scenario

PON-based FTTP is already being rolled out, but at different rates and with
technological variations, in different parts of the world. The main regions
currently are Asia-Pacific, North America and, to some extent, Europe.

Japan is where the real FTTP action is happening, largely
because of the government policies that help encourage broadband use, and
competition. In Japan, Nippon Telephone and Telegraph (NTT) is planning to
install PONs throughout its system, using equipment made by Lucent Technologies.

Other parts of Asia-Pacific-such as China, Korea, and
Australia
are in the early stages of FTTP
deployment.

Motorola has also extended its ultra-broadband innovation
with cable PON, a technology that delivers PON solutions customized to
accommodate existing cable infrastructures. Cable PON, a unique cable-driven
technology, delivers the business benefits of combined hybrid-fiber-coaxial (HFC)
and PON network architectures.

Verizon have announced that it would soon begin deploying
Gigabit passive optical network (GPON) technology that increases aggregate
speeds on FTTP systems by four times downstream to the customer, and by eight
times upstream, to support future enhancements to FiOS Internet services and
FiOS TV.

In India, Freescale Semiconductor has launched the industry's
first voice-enabled GPON. The company, along with Alcatel-Lucent, is
facilitating the adoption of FTTH technologies by availing jointly developed
GPON technology, and interoperability specifications to vendors of terminal
equipment worldwide.

Market Growth

The market for PON hardware is forecast to grow sharply. Worldwide
OLT and ONT PON equipment revenue reached $525 mn in 2004 and is projected to
grow to $2.2 bn in 2008, with port shipments reaching more than 8 mn.

PON is an attractive solution for high-bandwidth access
networks and also removes the need for expensive infrastructure upgrades.
Currently, service providers of all shapes and sizes are pushing fiber deeper
into their access networks to support the demand for video, online gaming, P2P
networking, and other bandwidth-intensive applications and PON could be a
solution for them.

Sandeep Budki

sandeepb@cybermedia.co.in