Special Report: Next Generation Internet Applications
4.2.2 Residential Access Networks Prospects for FITL services are growing within the United States. Several local exchange carriers are adopting ATM PONs for extending services to small businesses and residences. For example, BellSouth began a trial of PONs installed to 400 residential customers during 1999.[3] In December 1999, BellSouth increased its commitment to ATM PONs by awarding Marconi with a $1.0 billion contract for fiber-to-the-curb equipment.[40] Marconi's ATM PONs equipment delivers FITL voice, video, and data services to within 500 feet of the subscriber. The Marconi contract award brings the total number of FITL subscriber lines installed within the BellSouth service area to 780,000 lines. BellSouth will offer POTS and asymmetric digital subscriber line (ADSL) services over their FITL systems. The RBOC forecasts that it will deploy between 50,000 and 100,000 FITL access lines per year.[34] If fiber optic costs fall below the cost of new copper installation in 2002 as expected, then the remainder of the decade will see growing emphasis on FITL systems.
5.0 FUTURE OPTICAL NETWORK ARCHITECTURES Multiplexing is a method widely used within communications networks to combine many low bandwidth channels onto a higher bandwidth transmission medium. The process of combining many communications channels onto a higher capacity transmission medium is often called "capacity grooming." During the 1950s, the global communications infrastructure consisted largely of copper cable and analog microwave transmission systems primarily used for carrying Telex and telephone traffic. Bandwidth requirements per communications channel ranged from less than 100 bps for Telex to 3200 Hz for analog voice channels. Grooming during the 1950s and 1960s relied largely on frequency division multiplexing applied to coaxial cables and analog microwave systems.
Market forces drove the deployment of digital multiplexing within the global communications infrastructure. Introduction of digital microwave, digital switching systems, and the increasing popularity of telephone communications during the 1960s and the 1970s created the need for higher capacity, digital multiplexing methods. Widespread introduction of facsimile in the early 1980s compounded telephony growth and made the need for multiplexed transmission capacity through multiplexing more urgent.
Development of plesiochronous digital hierarchy (PDH) multiplexing systems in North America and Europe gave rise to new digital transmission channel formats. North America developed its PDH systems around the 1.544 Mbps, T1 format. The rest of the world adopted the International Telephone and Telegraph Consultative Committee (CCITT) standards (now known as the ITU-T standards) and deployed multiplex systems based upon the 2.048 Mbps E1 format. Both PDH formats were well suited to carrying voice, facsimile, and point-to-point dedicated data lines at 64 kbps or lower speeds. However, their usefulness declined after 64 kbps dedicated lines became too slow to meet market demands.
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