Metro optical networking revolution: architecture and enabling technology wish list

摘要

The last several years have seen much focus and deployment of DWDM technology in the long-haul space. This market was prime for this technology, given the immediate capacity constraints of legacy SONET/SDH architectures and extensive regeneration requirements. Undoubtedly, DWDM has yielded revolutionary advances in long-haul network capabilities, both in terms of increased capacity and dramatically-reduced regeneration costs. As long-haul network builds complete, many carriers are now focusing on metropolitan area networks to increase their revenue-generation base. Again, it is expected that DWDM technology will yield another revolution within this arena. Several years ago, the application of DWDM technology in the metropolitan space would have been cost-prohibitive, but continually decreasing optical component costs have largely mitigated these concerns. Nevertheless, the role of DWDM technology in the MAN will likely be very different as opposed to the long-haul space. One of the key differences between long haul and metropolitan networks is that the former are more transport-oriented, largely comprising point-to-point transport systems that handle relatively fixed high-speed tributary types (e.g., SONET/SDH circuits or OCh digital wrapper in the near future). Here, the key challenges pertain to transport quality and system capacity (number of wavelength, transmission distance, etc). Conversely, metropolitan networks are mostly ring-based and must evolve to support a much broader range of client protocols, with diverse bit-rates and encoding formats. Given their closer proximity to a continually-varying customer based, metropolitan networks must provide flexibility over differing topologies (rings, interconnection of rings) and efficiently handle multiple types of low-speed protocols over a common optical transport layer (e.g., SONET/SDH or OCh-based). In addition, cost sensitivities are a big concern, as the price per-bit-per-kilometer in the metropolitan area is much higher than that of long haul.