Fiber Deep Architectures and the Optical Node

Written by Tim Brophy, Product Manager Cable Access Business Unit

In a recent blog, we discussed Fiber Deep (FD) architectures and their place in the end-to-end network. We emphasized there that the physical topology is geared toward balancing the number of subscribers per service group, and that the capacity of each service group increases by the reduced number of subscribers served. Today, we want to explore the benefits of FD that illustrate the importance of the centrally located FD Node.

As we said, the physical location of the FD node creates RF node ports that serve approximately the same number of subscribers, but it also links the past and the future of the architectures. By this we mean that it leverages the existing HFC plant topology (the past) and prepares it for many more years of profitable service deployments (future). Operators and subscribers alike get multiple benefits from the centrally located smaller serving area of the FD node. The particular value depends on the details of deployments and service offerings, but all benefit from a reduction in failure group size and the reliability improvements associated with fewer active elements in the plant. The reduction in users sharing a common node does imply smaller statistical multiplexing gains, but this is more than offset by the increased cumulative capacity to which each user has access. The net result is an improved customer experience, reduced churn and improved competitive offerings.

We detail here some additional specific benefits:

In legacy plants, the FD node provides a logical location for separation of QAM and linear downstream signals and the combination of upstream signals for port and digital return efficiencies
In an R-PHY scenario (to be discussed in detail in a future post), FD nodes are ideally located for the digital-to-analog conversion function. They continue to derive value from the coax plant, while preparing the way for the future benefits of digital transport
The locations of FD nodes are close enough to each other that service groups can be combined at CMTS ports until market demands require complete segmentation; this will save cost for initial deployments. The proximity also means that operators can take advantage of digital multiplexing and provide path redundancy between nodes, thereby improving system reliability.
Flexibility of capacity is enhanced: once end-to-end connectivity is established, total capacity is controlled at the EDGES of the system (operators need ONLY touch the end points of their networks); if subscriber gear is self-installed, then only core access is required.
System administration is unified: control and management become a part of, and an extension to, the layer 2 control at the data center; packet optical protocols are now available end-to-end in both transport AND distribution networks.
Provisioning is simplified: the “touchless” addition of services, applications, and content provides rapid configuration to capture dynamic changes in demand and localization (e.g., local events, interest, or advertising domains)
- Simplified provisioning provides an opportunity to establish capacity-based billing, or
- Can be used to create separation among classes of service: incremental deployments for security-sensitive businesses or for “rogue” high-data volume consumers.
Smaller and common service group sizes ease the barriers to combining traditional CATV access plant with the Metro-E services, allowing for flexibility in physical plant, content-oriented provisioning, or connection-oriented links
Defines a logical and physical aggregation/furcation point for residential subscribers when franchise or demand-pull dictates a FTTH solution.
Establishes the launching point for future fiber to the curb, home, or business services.

The above benefits show the importance of the fiber deep node not only as hardware element itself, but also as an architectural element with topological significance. The well-chosen architectural location optimizes connectivity, powering, and anticipates future growth. The advantages are extended even further when the tie between fiber deep architectures and remote PHY is established. We’ll detail that in future blog, but in the meantime, consider the powerful combination of the above benefits with the watershed event defined by a move to an R-PHY node. This node is not just the end of a digital fiber link, but is established as a Network Element, replete with IP stack, signal grooming and new, intelligent methods of control, monitoring, and signal processing. As always, your Cisco account rep stands ready to help find the solution that works best for your network.

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