FTTX
FTTX
High speed Internet access and the desire to present a “one stop” shop for voice, video and data is pushing bandwidth demands throughout the telecommunications industry. Increased bandwidth demand in turn creates interest in deploying more fiber to the home (FTTX) equipment. FTTX offers much greater bandwidth than other broadband technologies such as DSL, VDSL and Cable Modems. Using Passive Optical Network (PON) architecture in FTTX deployments also offers lower operating costs by reducing the number of active components throughout the network. With PON architecture, all active components are placed at the ends of the fiber and passive optical splitters are placed in the field. PON technology also employs bi-directional communications over a single fiber strand. Fiber to the x (FTTX) is a generic term for any network architecture that uses optical fiber to replace all or part of the usual copper local loop used for telecommunications
There are two broad categories of FTTX Architectures - Active Ethernet and PON. In an Active Ethernet architecture, switches are arranged in a star configuration. In PON architecture, the services are delivered through a tree and branch configuration. Active Ethernet star configurations provide dedicated fibers between the end points and the Ethernet switch point of presence. These connections are usually 100 Mb/s or 1000 Mb/s. PON configurations use passive optical splitters to distribute the optical signal to each customer using splitting ratios up to 1:32.
PON Types
Three PON types are currently deployed in North America. BPON is based on ATM protocols and delivers up to 622 Mb/s downstream and 155 Mb/s upstream. Most of the carriers’ data networks at the time BPON started being deployed was ATM based. GE-PON is based on Ethernet and IP protocols and delivers symmetric 1.25 Gb/s. GE-PON complies with the IEEE 802.3ah standard. GPON complies with the ITU-T G.984 standard and delivers 2.5 Gb/s downstream and 1.25 Gb/s upstream.
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Active Ethernet
Active Ethernet networks usually have core routers in a central location then distribute the Ethernet pipes through a distribution network of Ethernet aggregation switches located closer to the subscribers similar to the placement of the splitter locations in a PON network. The main difference in the active network is that the switches require power and a certain level of maintenance where the splitters operate in a passive environment. Another feature of active Ethernet architecture is that each subscriber receives dedicated, bi-directional full bandwidth from the aggregation point. This subscriber bandwidth is limited by the port size provided by the aggregation switch and the uplink port of the aggregation switch. Depending on network design, the bandwidth available in the active Ethernet network is usually much greater than in a PON network. The bandwidth tradeoff is having the additional operational expenses for the active components.
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