HYBRID FIBER COAX: IS IT FUTURE PROOF?

摘要

As networks expand, hybrid fiber/coax (HFC) networks will be called upon to support a growingrange and volume of services. As demand increases for telephone, interactive digital, and datageneratingwork-at-home services, HFC networks will have to provide additional bandwidth.Today’s HFC networks are being designed with plenty of expansion capacity, allowing them to becost-effectively installed today, and economically augmented when necessary.The basic design of HFC networks maximizes utilization of the installed bandwidth. For example,modulation techniques can allow up to 240 DSOs per 6 Mhz, and up to eight digital, 4.0 megabitchannels per 6 Mhz of spectrum. As service requirements grow, the first amplifier on each of thefour legs of an optical node can, itself, become an optical node, carrying the full 750 MHz bandwidthto the subscribers it serves. By reducing the service area of the optical node, the availablebandwidth for subscribers is effectively quadrupled.Another often-cited concern is that of upstream capacity. This can be increased by a factor of upto four through the use of frequency block shifting. Using these and other techniques, the carryingcapacity of HFC networks can be easily expanded to support new services and growing demand.By deferring the expenditure until justified by demand, network providers can control capitalexpenditure without limiting performance.