How deep is fiber deep?

By Rajesh Abbi

March 29, 2017

The ever-increasing bandwidth demand in the broadband access networks is pushing the need for more and more fiber.

The ultimate goal for all operators is undoubtedly fiber-to-the-home (FTTH) – but, unfortunately, reality gets in the way. The high cost of building an all-fiber network is making everyone rethink the value proposition.

The cost of building access networks is a complex mix of many factors that vary by operator and by market.  Each operator has to carefully analyze their networks and market conditions to see where it makes sense to build fiber-to-the-home.

Given the fact that actual subscriber demand for most subscribers does not really require an all-fiber network – at least not yet, and the fact that enhancements in legacy network technologies are helping extend the performance of the legacy networks – most operators are taking an intermediate step of simply driving the fiber deeper in the network to meet the bandwidth requirements.

Telco operators have already been building fiber-to-the-node  (FTTN) and using VDSL (Very High Speed Digital Subscriber Line) technology to serve up to 100 Mbps at distances up to 500 meters.  The next step is to use the newly minted G.fast technology to drive data rates up to 1 Gbps – but that requires fiber to be driven all the way to the distribution point (FTTdp) within 100 meters of the home.

MSO operators have also been building FTTN HFC (Hybrid Fiber Coax) networks with fiber serving an optical node typically serving a node area with 500 – 1000 HHP (households passed).  The coax network from the optical node typically requires 5-6 HFC amplifiers along the path to the furthest home.  This is referred to as an N+5 or N+6 architecture, and can typically support a few hundred Mbps.  In order to serve Gigabit data rates, the fiber has to be driven deeper so that HFC amplifiers are no longer needed.  This is known as an N+0 architecture.  The new N+0 nodes will typically only serve node areas up to 64 HHP.

So, fiber is on the march.  Ultimately, how deep you drive fiber depends on the overall business case and the capabilities of the existing technologies which are constantly evolving.