HFC Technology
HFC technology is based on existing cable television(cable TV or CATV)technology.Originally,cable TV systems were based on coaxial cable facilities from an MSO to a customer premises and used a tree topology,most of these systems have been upgraded to HFC,by which the signal is brought to a fiber node via a pair of optical fibers and then distributed via coaxial cable to customers.At the head end,signals from various sources,such traditional satellite services,analog and digital services using WAN,and Internet service provider(ISP)services using private backbone network,are multiplexed and converted up from an electrical(radio frequency)signal to an optical signal.Communication si one way on the opticalfiber:each of a pair of optical fibers from the head end to the fiber node carries one-way traffic in opposite directions.The optical signal is conberted down to RF at the fiber node and travel over the coaxial cable in a duplex mode.The signal going from the head end to the customer premises if called a downstream signal or a forward path signal.The signal going from the customer premises to the head en di called an upstream signal or a reverse path signal.
译文：
因特网基础
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