Segmentation - xWDM Solutions for Every Community

Node segmentation is the first step for many cable operators in their quest to expand network capacity; it requires minimum network disruption yet has the potential to quadruple targeted services bandwidth (both down and upstream) with no construction costs. Node segmentation is enabled by WDM technologies — CWDM, DWDM, and the latest WDM technology, LcWDM^® — together with our scalable node platform.

Most CATV optical networks in use today today utilize 1310 nm links to connect the hub/headend and nodes. Traditionally, if the operator had wanted to increase the bandwidth of this network, it was necessary to put into operation a second fiber from the hub/headend to the node so that a second 1310 nm transmitter could be deployed in the downstream. With Aurora's LcWDM technology, the second fiber is no longer required. Now the cable operator simply has to replace the original 1310 nm transmitter with two LcWDM transmitters, and add the appropriate mux (no new fibers needed) to effectively double the downstream narrowcast capacity. (At the node, a second receiver and demux are needed.) Not only is this a very cost-effective solution since no fiber construction is required, it is also quickly implemented — typically completed within a maintenance window. By further adding LcWDM transmitters and node receivers, the node can be efficiently segmented into four in the downstream, quadrupling downstream bandwidth. Indeed, this technology has resulted in fibers being reclaimed and re-deployed to drive additional revenue (i.e., from businesses).

The upstream is even simpler; Aurora's industry-leading digital return technology is already optimized for segmentation. For initial network deployments, typically a "1-fer" will be deployed to save cost by using a cascade over fiber. Here, each of the four node returns is processed by the digital return transmitter and fed via one CWDM wavelength over a fiber to the headend. Replacing this transmitter with a "2-fer" will double the upstream bandwidth because a "2-fer" is effectively the functional equivalent of two "1-fers" but with their outputs TDM'd so that the signal can be fed back to the headend over just one CWDM wavelength. Quadrupling upstream bandwidth is made possible with the addition of a second "2-fer" transmitter with a different output wavelength. By multiplexing these two wavelengths together, only one upstream fiber is needed. Indeed, with the high cost associated with using fibers, Aurora has gone one step further; with our customized fiber tray and unique integrated passives, an MSO need only dedicate one fiber to each node yet still achieve full 4x4 node segmentation with downstream and upstream signals on one fiber.

Figure 1. 4x4 node segmentation on one fiber

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While the above scenario is the most popular for node segmentation, Aurora has pioneered DWDM architectures for those situations where fiber is very limited and hence additional wavelengths are needed (noting that up to 40 DWDM wavelengths can be carried on one fiber) and/or the reach exceeds the limits of both LcWDM and CWDM. Figure 2 highlights the traditional use of DWDM technology, a star topology, while Figure 3 details a special application of DWDM, "distributed DWDM" (or D²WDM). D²WDM is optimized for long reach neighborhoods with all the nodes being fed via just two fibers.

Figure 2. Single fiber capacity: 20 forward and 40 reverse segments

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Figure 3. D²WDM for special applications

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