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In telecommunications, radio frequency over glass (RFoG) is a deep-fiber network design in which the coax portion of the hybrid fiber coax (HFC) network is replaced by a single-fiber passive optical network (PON). Downstream and return-path transmission use different wavelengths to share the same fiber (typically 1,550 nm downstream, and 1,310 nm or 1,590/1,610 nm upstream). The return-path wavelength standard is expected to be 1,610 nm, but early deployments have used 1,590 nm. Using 1,590/1,610 nm for the return path allows the fiber infrastructure to support both RFoG and a standards-based PON simultaneously, operating with 1,490 nm downstream and 1,310 nm return-path wavelengths. ==Advantages== RFoG delivers the same services as an RF/DOCSIS/HFC network, with the added benefit of improved noise performance and increased usable RF spectrum in both the downstream and return-path directions. Both RFoG and HFC systems can concurrently operate out of the same headend/hub, making RFoG a good solution for node-splitting and capacity increases on an existing network. RFoG allows service providers to continue to leverage traditional HFC equipment and back-office applications with the new FTTP deployments. Cable operators can continue to rely on the existing provision and billing systems, Cable modem termination system (CMTS) platforms, headend equipment, set-top boxes, conditional access technology and cable modems while gaining benefits inherent with RFoG and FTTx. RFoG provides several benefits over traditional network architecture: * More downstream spectrum; RFoG systems support 1 GHz and beyond, directly correlating to increased video and/or downstream data service support * More upstream bandwidth; RFoG's improved noise characteristics allow for the use of the full 5–42 MHz return-path spectrum. Additionally, higher-performance RFoG systems not only support DOCSIS 3.0 with bonding, but also enable 64 quadrature amplitude modulation (QAM) upstream transmission in a DOCSIS 3.0 bonded channel, dramatically increasing return-path bandwidth. * Improved operational expenses; RFoG brings the benefits of a passive fiber topology. Removing active devices in the access network reduces overall power requirements, as well as ongoing maintenance costs that would normally be needed for active elements (such as nodes and amplifiers). Both cost savings and increased capacity for new services (revenue generating and/or competitive positioning) are driving the acceptance of RFoG as a cost-effective step on the path towards a 100-percent PON-based access network. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「radio frequency over glass」の詳細全文を読む スポンサード リンク
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