Triple-Play Service Deployment

38
Deploying and Troubleshooting Fiber Networks
Understanding FTTx networks and associated optical testing
The challenge of providing the increased bandwidth needed to
support triple-play service delivery is on-going and can be
daunting. Running optical fiber much deeper into the access
network, in some cases all the way to the customer premises, is an
important part of the strategy of nearly every service provider.The
appeal is that a fiber optic infrastructure offers the potential for
practically unlimited bandwidth and also facilitates greater
control over the operation, administration, and provisioning of the
access system.
FTTx Architectures
The general penetration of fiber into the access network is often
referred to as Fiber-to-the-X (FTTx). The actual architecture can
vary depending on the depth of penetration (see Figure 3.1). In an
FTTx architecture, the optical line terminal (OLT) houses the laser
transmitters which are dedicated to individual users in a point-topoint
(P2P) network or shared in a passive optical network (PON).
The optical fiber running to the users includes several
components: the feeder cable which terminates at the OLT, the
distribution cable which comprises the majority of the access
network, and the drop cable which connects users or remote
distribution points. In FTTH, the optical network terminal (ONT)
receives the signal from the OLT and converts it into usable
electronic signals for voice, video, and data at the customer
premises. If the last mile is provided by a copper access network,
the fiber is terminated at an optical network unit (ONU), often
consisting of a digital subscriber line access multiplexer (DSLAM),
which services the copper network and is located at a remote
central office (RCO).