Powering The Plant: HFC Versus FTTH - ISE Magazine

Choosing the most energy efficient network architecture

As subscribers continue to demand more and more network bandwidth, operators of hybrid-fiber-coax (HFC) networks have some big decisions to make. Should they upgrade their plant to a next-generation HFC architecture, or deploy a Fiber to-the-Home (FTTH) architecture leveraging passive optical networks (PONs)?

Over the last 12-18 months, adoption of 10G XGS-PON has grown at a 4x-5x rate year over year as operators are increasingly choosing to deploy fiber-based PON networks. We see operators deploying 10G PON in a greenfield mode for new markets/coverage areas, or as an overlay in an existing market to address near-term network needs while future proofing the network and facilitating their migration from HFC over time.

With this explosive level of adoption taking place, operators are clearly making the decision to place big bets on FTTH & PON as the access technology of choice for the coming decades.

But pulling the trigger and making these investments require solid business cases and ROI justification. Beyond the technology benefits driven by FTTH PON, there must be compelling economic factors motivating aggressive moves by large numbers of operators.

While much has been written about the comparative capital costs of constructing these upgrades and new networks, less has been discussed documenting the ongoing operating costs, which over the life of the investment make up the bulk of the overall network expense. We all know, intuitively, that fiber should cost far less than metallic networks in terms of maintenance. However, the largest difference in operating expense is in an area which may surprise you: powering the plant.

HFC networks, old and new, require power to run the nodes and the amplifiers. Because these elements are located in the outside plant, a distributed power solution is required. Power supplies are distributed throughout the plant, with each serving a cluster of nodes and/or amplifiers. In most cases, back-up batteries protect against outages in the commercial power source. These batteries have a finite life and require periodic replacement.

In contrast, PONs are, by definition, "passive". An Optical Line Terminal (OLT) located in a central office or headend feeds the fiber plant. There are no amplifiers or other electronics in the plant, so there is nothing to power.

When adding PON as an overlay network to eventually replace an existing HFC network, it is desirable to make as much use of the installed fiber as possible. Installed spare fiber counts are probably far short of what is required for a PON. A remote OLT (ROLT) solution can serve to multiply these fibers to provide PON service without large-count extensions. In this case, power in the field will be required. How does that power requirement impact the savings of PON versus HFC?

Let us quantify the power used for HFC networks and see what could be saved if the same plant geography was instead served by a fiber-based PON network.

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