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by Jim Farmer, special to Network World

FTTP boosts bandwidth in the last mile

How-To
Jul 12, 20043 mins
Broadband

Fiber to the premises extends fiber cabling all the way to homes or businesses. Because fiber provides a significant bandwidth boost over twisted-pair or coaxial connections used in the last mile, carriers are tapping it to deliver voice, video and data services.

Although many service providers now offer business-class broadband services, corporation haven’t widely adopted these DSL and cable modem services because they provide relatively limited bandwidth and scalability.

But one emerging form of broadband could change that. Fiber to the premises (FTTP) extends fiber cabling all the way to homes or businesses. Because fiber provides a significant bandwidth boost over twisted-pair or coaxial connections used in the last mile, carriers are tapping it to deliver voice, video and data services.

FTTP offers speeds of 25M to 50Mbit/sec or greater, as compared with a maximum of about 5M to 6M bit/sec for other types of broadband services. FTTP also supports fully symmetric services.

There are several architectures for FTTP systems, but all start with an optical line termination (OLT) device. An OLT device acts as a switch, and interfaces with the Internet and other systems via standard interconnections such as Ethernet or ATM. Service providers could place one OLT device in a central office and another in the field closer to subscribers to provide a longer reach between the central office and customers.

Most FTTP systems employ passive splitting in the field. An optical splitter divides the FTTP signal among multiple homes and businesses. At the subscriber site – a business or home – an optical network unit (ONU) converts optical signals to standard forms that can be used by customers. These generally include Ethernet (10/100/1000Base-T), plain old telephone service lines for voice and cable TV-like signals for video.

Using FTTP, service providers can deliver analog and digital video that is compatible with what cable TV systems provide.

Voice quality is as good or better than what traditional phone companies provide. This is a result of QoS features and the fact that voice signal is digitized closer to subscribers, eliminating signal degradation.

With FTTP, QoS mechanisms control the data rate provided to each subscriber, and rates can be set in increments as low as 64K bit/sec.

FTTP also lets service providers offer different bandwidth to different applications used by the same subscriber. This is enabled by QoS techniques that identify traffic based on source, destination, application or Differentiated Services.

What’s more, network operators also can use QoS classification to create premium services. For example, one service might prioritize corporate VPN traffic for telecommuters or prioritize traffic to a business Web site over e-mail exchanges.

Layer 3 bandwidth management lets FTTP networks support other services as well, such as IP Centrex, IP phones, conferencing, Web-based call management and Web-based subscriber self-care.

As IP over Gigabit Ethernet has reached maturity and all network architectures continue to migrate toward IP, more FTTP platforms are incorporating Ethernet technology to take advantage of various capital and operational savings. Ethernet components are less expensive than ATM counterparts and offer substantial savings in terms of fiber deployment and management – two more factors that will help fuel the growth of FTTP networks.

Farmer is CTO of Wave7 Optics. He can be reached at jim.farmer@w7optics.com.