ATLANTA, Ga. -- Gigabit Cities Live! 2015 -- When Verizon introduced FiOS in 2005, the company's fiber network expansion was immediately visible to the world. But Comcast has been pushing fiber deeper into its network for years, and while the company hasn't widely advertised the fact, that investment is now making it possible for Comcast to push out multi-gigabit services with a goal of making its Gigabit Pro service available to 18 million homes by the end of the year. (See Comcast Preps 2-Gig Service… Over Fiber.)

Here in Atlanta Wednesday morning, Comcast Vice President of Network Architecture Rob Howald was cautious about quantifying the operator's fiber reach. He did acknowledge, however, that in select gigabit markets, the company is driving fiber deep enough into its network that each node ends up serving only about 100 subscribers. That's significantly smaller than a typical serving group size for cable operators, which can range anywhere from 250 subscribers to 500 or more.

Howald also noted that Comcast is looking at additional markets where it can follow the same strategy, which includes deploying a node-plus-zero (N+0) architecture. N+0 means there are no amplifiers required between a node and a subscriber household -- a calculation that indicates just how close fiber is getting to each subscriber's front door.

In addition to pushing fiber deeper into the network, Comcast is also deploying 1GHz nodes in its gigabit markets and it's evaluating the case for 1.2GHz nodes. Howald said Comcast doesn't need access to that additional spectrum today, but that as a future-proofing step, 1.2GHz could make sense.

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As for other bandwidth expansion techniques, Howald believes Comcast will pull the trigger on MPEG-4 deployments in more markets going forward. The company is currently running an MPEG-4 trial in Augusta, but has said very little about what that could mean for the rest of its footprint. Howald noted that moving to MPEG-4 is relatively easy to do and is a cost-effective way to regain bandwidth. Many of the set-tops that Comcast has in the field already support MPEG-4, and have so for years. (See Prepping for D3.1, Cox Expands All-Digital .)

While offering gigabit services wasn't even on the agenda a short while ago, Comcast has nevertheless been laying the groundwork for massive speed upgrades for years. Deeper fiber is a big part of that equation and Comcast will determine market by market just what it needs to bridge the rest of the gap.

— Mari Silbey, Senior Editor, Cable/Video, Light Reading