Fiber to the x
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Fiber to the x (FTTX) is a generic term for any broadband network architecture using optical fiber to replace all or part of the usual metal local loop used for last-mile telecommunications. The term is a generalization for several configurations of fiber deployment, ranging from FTTN (fiber to the neighborhood) to FTTD (fiber to the desk).
The telecommunications industry differentiates between several distinct configurations. The terms in most widespread use today are:
- FTTN/FTTLA (fiber-to-the-node, -neighborhood, or -last-amplifier): Fiber is terminated in a street cabinet, possibly miles away from the customer premises, with the final connections being copper. FTTN is often an interim step toward full FTTH and is typically used to deliver advanced triple-play telecommunications services.
- FTTC/FTTK (fiber-to-the-curb/kerb, -closet, or -cabinet): This is very similar to FTTN, but the street cabinet or pole is closer to the user's premises, typically within 1,000 feet (300 m), within range for high-bandwidth copper technologies such as wired ethernet or IEEE 1901 power line networking and wireless wi-fi technology. FTTC is occasionally ambiguously called FTTP (fiber-to-the-pole), leading to confusion with the distinct fiber-to-the-premises system.
- FTTB (fiber-to-the-building, -business, or -basement): Fiber reaches the boundary of the building, such as the basement in a multi-dwelling unit, with the final connection to the individual living space being made via alternative means, similar to the curb or pole technologies.
- FTTH (fiber-to-the-home): Fiber reaches the boundary of the living space, such as a box on the outside wall of a home. Passive optical networks and point-to-point ethernet are architectures that deliver triple-play services over FTTH networks directly from an operator's central office.
- FTTP (fiber-to-the-premises): This term is used either as a blanket term for both FTTH and FTTB, or where the fiber network includes both homes and small businesses.
- FTTD (fiber-to-the-desk): Fiber connection is installed from the main computer room to a terminal or fiber media converter near the user's desk.
To promote consistency, especially when comparing FTTH penetration rates between countries, the three FTTH Councils of Europe, North America, and Asia-Pacific agreed upon definitions for FTTH and FTTB in 2006, with an update in 2009. The FTTH Councils do not have formal definitions for FTTC and FTTN.
To some, fiber to the telecom enclosure (FTTE) is not considered to be part of the FTTX group of technologies, despite the similarity in name. FTTE is a form of structured cabling typically used in the enterprise local area network, where fiber is used to link the main computer equipment room to an enclosure close to the desk or workstation.
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The speeds of fiber-optic and copper cables are both limited by length, but copper is much more sharply limited in this respect. For example, the common form of gigabit ethernet (1Gbit/s) runs over relatively economical category 5e, category 6, or augmented category 6 unshielded twisted-pair copper cabling but only to 300 ft (91 m). However, 1Gbit/s ethernet over fiber can easily reach tens of miles.
Even in the commercial world, most computers have short copper communication cables, typically under 100 ft (30 m). Most metropolitan network links (e.g., those based on telephone or cable television services) are several miles long, in the range where fiber significantly outperforms copper. Replacing at least part of these links with fiber shortens the remaining copper segments and allows them to run much faster.
Fiber configurations that bring fiber directly into the building can offer the highest speeds since the remaining segments can use standard ethernet or coaxial cable. Fiber configurations that transition to copper in a street cabinet are generally too far from the users for standard ethernet configurations over existing copper cabling. They generally use very high bitrate digital subscriber line (VDSL) at downstream rates of well over 20Mbit/s. Experimental programs such as Google Fiber plan to offer 1000/1000 Mbit/s symmetrical connections directly to consumer homes.
Fiber is often said to be "future-proof" because the data rate of the connection is usually limited by the terminal equipment rather than the fiber, permitting at least some speed improvements by equipment upgrades before the fiber itself must be upgraded. Still, the type and length of employed fibers chosen, e.g., multimode vs. single-mode, are critical for applicability for future connections over 1Gbit/s.
Ethernet point-to-point 
Point-to-Point Protocol over Ethernet (PPPoE) is a common way of delivering triple- and quad-play (voice, video, data, and mobile) services over both fiber and hybrid fiber-coaxial (HFC) networks. Active PPPoE uses dedicated fiber from an operator's central office all the way to the subscribers' homes, while hybrid networks (often FTTN) use it to transport data via fiber to an intermediate point to ensure sufficiently high throughput speeds over last-mile copper connections.
This approach has become increasingly popular in recent years with telecoms service providers in both North America (AT&T, Telus, for example) and Europe's Fastweb, Telecom Italia, Telekom Austria and Deutsche Telecom, for example. Google has also looked into this approach, amongst others, as a way to deliver multiple services over open-access networks in the United States.
Fiber to the node 
Fiber to the node or neighborhood (FTTN), sometimes identified with and sometimes distinguished from fiber to the cabinet (FTTC), is a telecommunication architecture based on fiber-optic cables run to a cabinet serving a neighborhood. Customers typically connect to this cabinet using traditional coaxial cable or twisted-pair wiring. The area served by the cabinet is usually less than one mile in radius and can contain several hundred customers. (If the cabinet serves an area of less than 1,000 ft (300 m) in radius, the architecture is typically called FTTC/FTTK.)
FTTN allows delivery of broadband services such as highspeed internet. Highspeed communications protocols such as broadband cable access (typically DOCSIS) or some form of digital subscriber line (DSL) are used between the cabinet and the customers. The data rates vary according to the exact protocol used and according to how close the customer is to the cabinet.
Unlike FTTP, FTTN often uses existing coaxial or twisted-pair infrastructure to provide last-mile service and is thus less costly to deploy. In the long term, however, its bandwidth potential is limited relative to implementations that bring the fiber still closer to the subscriber.
A variant of this technique for cable television providers is used in a hybrid fiber-coaxial (HFC) system. It is sometimes given the acronym FTTLA (fiber-to-the-last-amplifier) when it replaces analog amplifiers up to the last one before the customer (or neighborhood of customers).
Fiber to the curb 
Fiber to the curb (FTTC) is a telecommunications system based on fiber-optic cables run to a platform that serves several customers. Each of these customers has a connection to this platform via coaxial cable or twisted-pair. The "curb" is an abstraction and can just as easily mean a pole-mounted device or communications closet or shed. Typically any system terminating fiber within 1,000 ft (300 m) of the customer premises equipment would be described as FTTC.
FTTC allows delivery of broadband services such as highspeed internet. Usually existing wire is used with communications protocols such as broadband cable access (typically DOCSIS) or some form of DSL connecting the curb/cabinet and the customers. In these protocols, the data rates vary according to the exact protocol used and according to how close the customer is to the cabinet.
Where it is feasible to run new cable, both fiber and copper ethernet are capable of connecting the "curb" with a full 100Mbit/s or 1Gbit/s connection. Even using relatively cheap outdoor category 5 copper over thousands of feet, all ethernet protocols including power over ethernet (PoE) are supported. Most fixed wireless technologies rely on PoE, including Motorola Canopy, which has low-power radios capable of running on a 12VDC power supply fed over several hundred feet of cable.
Power line networking deployments also rely on FTTC. Using the IEEE P1901 protocol (or its predecessor HomePlug AV) existing electric service cables move up to 1Gbit/s from the curb/pole/cabinet into every AC electrical outlet in the home - coverage equivalent to a robust Wi-Fi implementation, with the added advantage of a single cable for power and data.
FTTC is subtly distinct from FTTN or FTTP (all are versions of fiber in the loop). The main difference is the placement of the cabinet. FTTC will be placed near the "curb", which differs from FTTN placed far from the customer, and FTTP placed directly at the serving location.
Unlike FTTP, FTTC can use the existing coaxial, twisted-pair or AC power line infrastructure to provide last-mile service. The G.hn and IEEE P1905 efforts were attempts to unify these existing cables under one management protocol.
By avoiding new cable and its cost and liabilities, FTTC costs less to deploy. However, it also has historically had lower bandwidth potential than FTTP. In practice, the relative advantage of fiber depends on the bandwidth available for backhaul, usage-based billing restrictions that prevent full use of last-mile capabilities, and customer premises equipment and maintenance restrictions, and the cost of running fiber that can vary widely with geography and building type.
In the United States of America and Canada, the largest deployment of FTTC was carried out by BellSouth Telecommunications. With the acquisition of BellSouth by AT&T, deployment of FTTC will end. Future deployments will be based on either FTTN or FTTP. Existing FTTC plant may be removed and replaced with FTTP. Verizon, meanwhile, announced in March 2010 they were winding down Verizon FiOS expansion, concentrating on completing their network in areas that already had FiOS franchises but were not deploying to new areas, suggesting that FTTH was uneconomic beyond these areas.
Verizon also announced (at CES 2010) its entry into the smart home and power utility data management arenas, indicating it was considering using P1901-based FTTC or some other existing-wire approach to reach into homes, and access additional revenues from the secure AES-128 bandwidth required for advanced metering infrastructure. However, the largest 1Gbit/s deployment in the United States, in Chattanooga, Tennessee, despite being conducted by power utility EPB, was FTTH rather than FTTC, reaching every subscriber in a 600-square-mile area. Monthly pricing of $350 reflected this generally high cost of deployment.
Historically, both telephone and cable companies avoided hybrid networks using several different transports from their point of presence into customer premises. The increased competitive cost pressure, availability of three different existing wire solutions, smart grid deployment requirements (as in Chattanooga), and better hybrid networking tools (with major vendors like Alcatel-Lucent and Qualcomm Atheros, and Wi-Fi solutions for edge networks, IEEE 1905 and IEEE 802.21 protocol efforts and SNMP improvements) all make FTTC deployments more likely in areas uneconomic to serve with FTTP/FTTH. In effect FTTC serves as a halfway measure between fixed wireless and FTTH, with special advantages for smart appliances and electric vehicles that rely on PLC use already.
Fiber to the premises 
Fiber to the premises (FTTP) is a form of fiber-optic communication delivery, in which an optical fiber is run in an optical distribution network from the central office all the way to the premises occupied by the subscriber. The term "FTTP" has become ambiguous and may also refer to FTTC where the fiber terminates at a utility pole without reaching the premises.
FTTH vs. FTTB 
Fiber to the premises can be categorized according to where the optical fiber ends:
- FTTH (fiber to the home) is a form of fiber-optic communication delivery that reaches one living or working space. The fiber extends from the central office to the subscriber's living or working space. Once at the subscriber's living or working space, the signal may be conveyed throughout the space using any means, including twisted-pair, coaxial cable, wireless, power line communication, or optical fiber.
- FTTB (fiber to the building or basement) is a form of fiber-optic communication delivery that necessarily applies only to those properties that contain multiple living or working spaces. The optical fiber terminates before actually reaching the subscribers living or working space itself, but does extend to the property containing that living or working space. The signal is conveyed the final distance using any non-optical means, including twisted-pair, coaxial cable, wireless, or power line communication.
An apartment building may provide an example of the distinction between FTTH and FTTB. If a fiber is run to a panel at each subscriber's apartment unit, it is FTTH. If instead the fiber goes only as far as the apartment building's shared electrical room, it is FTTB.
- Fastweb: Italian operator Fastweb launched the first commercial FTTH service in 2001. Using PPPoE architecture, the service delivered voice, video and data services to thousands of subscribers' homes in Italy over a 100 Mbit/s fiber connection. Fastweb used one of the first residential gateways for both multi-dwelling units as well as residential homes that provided embedded fiber termination, designed and built by Advanced Digital Broadcast, to enable consumers to share services with a range of consumer electronics devices around the home. The deployment of an FTTH network meant Fastweb was the first telecom operator to deliver true triple-play services to its subscribers. This contributed to its ARPU [Average Revenue Per User] being amongst the highest in the industry for a number of years during the early 2000s. Its FTTH network also puts it at the forefront of advanced connected home services. On September 13, 2012 the company announced a national ultra-broadband FTTS/FTTH initiative with the stated goal of offering 100 Mbit/s connections to 5.5 million Italian subscribers by .
- Fiber for Italy: The Fiber for Italy Initiative has the stated goal of offering 100 Mbit/s symmetrical connections to 10 million Italian subscribers across 15 cities by  and up to 1Gbit/s for business customers. It involves operators Wind, Tele2, Vodafone and Fastweb. An ongoing pilot project in the Italian capital Rome delivers symmetrical speeds of up to 100 Mbit/s to small businesses. Italian state operator Telecom Italia is not a participant in the Fiber for Italy program, but has independently committed to provide ultra-highspeed broadband up to 100 Mbit/s symmetrical connections to 50 percent of the country's population (138 cities) by 2018. Both Fiber for Italy participants and Telecom Italia are working with Advanced Digital Broadcast to provide residential gateway technology with embedded fiber termination. Since 2006, Television Sierre SA deploys a FTTH network in most municipalities in the district of Sierre in Switzerland. Triple Play services are offered to the public under the brand Vario.
- Slovakia: Orange in 2007 decided to build FTTH in the country. In the 2010 was coverage up to 310,000 households, almost 19% of the country. In the end of 2011 the major operators (Orange, Deutsche Telekom AG) cover up to 350,000 households. The prices start at 14.99€ for 100/10 Mbit/s (new customers only 100/4Mbit/s). Some smaller ISPs offer up to 1Gbit/s on a symmetric line for 30€.
- In October 2011, British operator Hyperoptic launched a 1Gbit/s FTTH service in London.
- In 2011, Mexican operator Telmex launched the FTTH service for its costumers in Mexico City, and in other major cities in Mexico.
- Bell Canada uses the Alcatel-Lucent 7330 ISAM video-ready access device, and provides Internet service via FTTH to 175 Mbit/s.
- AT&T provides FTTP and FFTN service through its U-verse service in 22 U.S. states.
- In October 2012, British operator Gigler UK launched a 1Gbit/sec down and 500Mbit/sec up service in Bournemouth using the CityFibre network.
FTTN or FTTC 
FTTN is currently used by a number of multiple-service operators to deliver advanced triple-play services to consumers, including AT&T in the United States for its U-Verse service, Deutsche Telekom in Germany, Swisscom, and Canadian operators Telus and Bell Canada. It is seen as an interim step towards full FTTH and in many cases triple-play services delivered using this approach have been proven to grow subscriber numbers and ARPU considerably.
Optical distribution networks 
Direct fiber 
The simplest optical distribution network architecture is direct fiber: each fiber leaving the central office goes to exactly one customer. Such networks can provide excellent bandwidth but are about 10% more costly due to the fiber and central office machinery.
Direct fiber is generally favored by new entrants and competitive operators. A benefit is that no layer 2 networking technologies are excluded, whether passive optical network (PON), active optical network (AON), or other. Any form of regulatory remedy is possible using this topology.
More commonly, each fiber leaving the central office is actually shared by many customers. It is not until such a fiber gets relatively close to the customers that it is split into individual customer-specific fibers. AONs and PONs both achieve this split.
Active optical network 
AONs rely on electrically powered network equipment to distribute the signal, such as a switch or router. Normally, signals need optical-electrical-optical transformation in the AON. Each signal leaving the central office is directed only to the customer for whom it is intended.
Incoming signals from the customers avoid colliding at the intersection because the powered equipment there provides buffering. Active ethernet (a type of ethernet in the first mile) is a common AON, which uses optical ethernet switches to distribute the signal, incorporating the customers' premises and the central office into a large switched ethernet network.
Such networks are identical to ethernet computer networks used in businesses and academic institutions, except that their purpose is to connect homes and buildings to a central office rather than to connect computers and printers within a location. Each switching cabinet can handle up to 1,000 customers, although 400-500 is more typical.
This neighborhood equipment performs layer 2 switching or layer 3 switching and routing, offloading full layer 3 routing to the carrier's central office. The IEEE 802.3ah standard enables service providers to deliver up to 100Mbit/s, full-duplex, over one single-mode optical fiber FTTP, depending on the provider. Speeds of 1Gbit/s are becoming commercially available.
Passive optical network 
A passive optical network (PON) is a point-to-multipoint FTTP network architecture in which unpowered optical splitters are used to enable a single optical fiber to serve up to 128 customers. A PON reduces the fiber and central office equipment required compared with point-to-point architecture.
Downstream signal coming from the central office is broadcast to each customer premises sharing a fiber. Encryption is used to prevent eavesdropping.
Upstream signals are combined using a multiple-access protocol, usually time division multiple access (TDMA).
Electrical network 
Once on private property, the signal typically travels the final distance to the end-user's equipment using an electrical format.
The optical network terminal (ONT, an ITU-T term) or unit (ONU, an identical IEEE term) converts the optical signal into an electrical signal using thin film filter technology. These units require electrical power for their operation, so some providers connect them to backup batteries in case of power outages to ensure emergency access to telecommunications. The optical line terminations "range" the optical network terminals or units in order to provide TDMA timeslot assignments for upstream communication.
For FTTH and for some forms of FTTB, it is common for the building's existing phone systems, local area networks, and cable TV systems to connect directly to the optical network terminal or unit.
If all three systems cannot directly reach the unit, it is possible to combine signals and transport them over a common medium. Once closer to the end-user, equipment such as a router, modem, or network interface controller can separate the signals and convert them into the appropriate protocol.
With VDSL, for example, the combined signal travels through the building over existing telephone wiring until it reaches the end-user's living space, where a VDSL modem converts data and video signals into ethernet protocol, which is sent over the end-user's category 5 cable. A network interface module converts video signal into radio frequency that is sent over the end-user's coaxial cable.
The combined signal can travel over the phone wiring through DSL splitters to separate the video and data signals from the voice signal; over coaxial cable; or to VOIP phones that can plug directly into the local area network.
See also 
- FTTH networking: Active Ethernet versus Passive Optical Networking and point-to-point vs. point-to-multipoint - Telecompaper
- Active Ethernet grows in PON's shadow
- "FTTH Council - Definition of Terms". FTTH Council. August 11, 2006. Retrieved September 1, 2011.
- "FTTH Council - Definition of Terms". FTTH Council. January 9, 2009. Retrieved September 1, 2011.
- All multimode fiber is not created equal
- da Silva, Henrique (March, 2005), Optical Access Networks, Instituto de Telecomunicações, p. 10. Retrieved on 2007-03-25.
- McCullough, Don (August, 2005), "Flexibility is key to successful fiber to the premises deployments", Lightwave 22 (8). Retrieved on 2010-01-27.
- Analyst: AT&T may replace some FTTC with FTTP
- Pirelli Broadband Solutions è il partner tecnologico di Fastweb per la nuova rete a banda larga >> Scienze e Tecnologie - Tecnologie informatiche - Telecomunicazioni :: Nannim...
- Italy gets fiber back on track | TelecomsEMEA.net
- Pirelli Broadband Solutions, the technology partner of fastweb network Ngan | Free VoIP International Phone Calls by VoIP Service Providers
- 1Gbit/sec broadband lands in London
- Bell Internet Packages
- Facts and Figures 2010
- http://2010.swisscom-report.ch/en/financial-year-2010 [page 22]
- Best-Ever Mobile Broadband Sales and Strong Cash Flows Highlight AT&T's Fourth-Quarter Results; Stock Buyback Begins on Previous 300 Million Share Authorization
- The Economics of Next Generation Access
- Developments in Fiber Technologies and Investment
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