By Chris Bonang, Harmonic, Inc.
As consumer demand for services such as high-speed internet access, multiple voice lines, and video on demand continues to grow, HFC networks are increasingly being recognized worldwide as the only single, proven, residential access network that can deliver the enormous bandwidth necessary to supply these services. Any network built today must be future proof , capable of scaling to whatever amount of bandwidth that will be necessary to support any future services and applications that may appear in the next 10-15 years. Even in existing HFC systems with extensive legacy equipment, it is possible to apply solutions developed for new builds when planning system upgrades. In this paper, optimal HFC designs for such greenfield builds are reviewed. The expected growth in bandwidth demand from cable subscribers over the next several years is first reviewed. Deep fiber optical node segmentation schemes which will allow highly scalable bandwidth delivery, and at the same time minimize or eliminate RF actives from the coax plant are then discussed. It is then shown how DWDM can provide significant cost savings and deployment convenience by reducing costly hub real estate and minimizing or eliminating expensive SONET transmission systems. Cost-effective implementation of a combination of digital transmission and DWDM in the return path of such deep fiber architectures is examined. Finally, the discussion of digital return is extended to include the possibility of demodulation, and even reduced CMTS functionality, in the node.