Practical considerations in the European market for building
and future-proofing robust, flexible FTTN infrastructures
The European market presents service providers with some unique challenges
in pushing fiber closer to the end user. With virtually no overhead distribution
and very little buried fiber cable, a new physical plant is unlikely. Rather, service
providers are seeking the best way to use existing ducted infrastructure—and
network planners must be willing to consider what architectures will best serve
their needs today and in the foreseeable future.
ADC has taken the lead in successfully developing equipment and systems that
meet the needs of service providers worldwide—each with their own unique
set of challenges. Although, from a practical standpoint, FTTN architectures in
Europe differ substantially from other parts of the world, there are some issues
that planners need to consider in the early stages of planning how best to get
fiber closer to the subscriber.
Ducts are here to stay
Most areas of Europe have copper cabling that runs through an intricate system
of buried ducts between nodes. Historically, the network planners have only run
fiber—a straight cable and a straight splice—from one building they own to
another building they also happen to own. A distributed architecture that feeds
multiple nodes and offers redundant routes has not really been a viable option
for them.
Building fiber rings where there has never been fiber is an expensive and
disruptive operation. To deploy the ducts necessary to build any ring architecture
would require tearing up both public and private property to link the trees and
branches of the network. Even running fiber down existing copper-filled duct
lines presents challenges and offers little in terms of flexibility or easy fiber access
for reconfigurations or troubleshooting.
Still, like elsewhere in the world, service providers in Europe are facing the
task of building next-generation networks to increase available bandwidth by
getting active equipment closer to the customer. New services are demanding
a conversion from copper to fiber which, in turn, is placing the burden on

A typical copper distribution duct system begins at
the CO with multiple ducts running out a specified
distance before some of the ducts branch out into other
directions. Therefore, it’s not one cable running in one
duct to one group of cabinets. Rather, it is multiple ducts
containing multiple cables that share the infrastructure
for part of the length and then branch in different
directions.
These radial feeds from the CO provide coverage to a
nominal circular area of between four and eight cabinets
per main cable. The reach from the CO is approximately
4-5 km, dictated by the cable gauge. Two or more main
cables might feed in the same direction, varying only in
overall length or reach. One main cable would feed the
closer cabinets while the other feeds the more distant
cabinets. For example, there might be 35,000 copper
pairs leaving a CO on 20 main cables of various sizes.
With those 20 cables, providers are able to feed 80 to
100 cabinets.
Converting to fiber
When converting the service area to FTTN, the same rule
applies in Europe as with other geographical areas—
loops have to be cut back to below 5000 feet.
For ADSL or VDSL services, distances must be within
1.5 km from the equipment to the customer. Since
existing CO areas are typically about 5 km, fiber feeds
would have to be built to service the outer two-thirds
of the customers. Basically, the CO would feed the closer
third of the customers, but the other two-thirds would
require conversion to active cabinets.

also provide an easier means to achieve redundancy, as
we’ll discover later in this paper.
400-2,400 Pair x “n”
Central Office
PCP
PCP
PCP
PCP
PCP
PCP
2,400 Pair
1,200 Pair
800 Pair
400 Pair
400 Pair
800 Pair
400 Pair
Practical considerations in the European market for building and future-proofing robust, flexible FTTN infrastructures
Page 3
Patch or splice?
Finally, there is the age-old consideration of whether to
splice or patch (connect) cables. Again, many service
providers have their own rules and standards. In a patch,
the cable is brought above ground into a patch cabinet.
The alternative is to splice it in an underground splice
closure. Since the mindset in Europe has always been
a simple building to building connection, every fiber
would be typically spliced to the exact same fiber in the
next section. But when the requirement is to provide
services to small groups of houses in a tree and branch

the physical infrastructure. A secondary fiber cross-
connect point (SFCC) is also shown in Figure 2 where the
second cable branches in several different directions.
Possible second fiber
cross-connect point
Central Office > 2 km
PCP
PCP
PCP
PCP
PCP
PCP
PCP
PCP
PCP
PCP
PCP
Create fiber
cross-connect point
Typical multiple
way duct route
Figure 2: Establishing fiber cross-connect points increases network flexibility and utilization, and reduces operational costs.
Achieving redundancy
Achieving redundancy in a tree and branch network systems can be done by first giving consideration
to cable size—for example, using two 144-count cables instead of a single 288-count cable. By bringing
the two 144-count cables above ground into a fiber cabinet, the tubes in each cable can be split out.
By putting 72 fibers of the first cable onto the second cable and vice versa, a second functional route is
formed downstream. Should a break occur in either feeder cable, a redundant path is now available.
Further redundancy can also occur farther downstream. In Figure 2, the one main feeder cable passing
through the MFFC continues to the SFCC. At this junction, the fiber tubes can be split once again to