Installation guide

Fiber Solutions

FTTH Application Guide

underlying technology. This section attempts to define some general items to

take into consideration, not to be a definitive resource. We also add an

appendix to discuss these topics in greater detail to broach the subject and

help locate reference resources with quickly evolving technologies.

GPON and Active Ethernet networks and terminology

There is a set of terminology for components in optical deployment network

(ODN).

Components of optical deployment networks.

Optical networks are comprised of a number of components between the

subscriber CPE devices. GPON networks have additional components for

splitting signals (splitters).

• OLT

Optical Line Terminator. This device is considered the head end of the

ODN.

• Optical fiber

The optical fiber is the physical cable.

• Splitters (GPON only)

Optical splitters split a single optical signal to multiple optical signals.

• Couplers

Couplers are connectorized means for splicing cables. Because couplers

are connectors there is a an optical signal cost for connectors

• ONT or ONU

Optical Network Terminator (ONT) and Optical Network Unit (ONU) are

reasonably similar terms which are both defined in the ITU-T G.984

GPON standards. They both provide an end for the ODN and conversion

to some electrical media; However, ONTs usually have multiple

subscriber-side services and interfaces, like Ethernet LAN, POTS or

coaxial cable for TV services. ONUs would have a GPON interface

upstream (just like the ONT), but would connect to some other last mile

copper access device, such as a VDSL2 DSLAM or MSAP.

• Attenuators

Attenuation is the term for the loss of optical power on the ODN. Some

devices may actually receive too high a signal power strength for the

receiving device. This situation most commonly occurs in lab settings,

such as we are building for the scenarios in this guide. An attenuator is

actually a device that can adjust the power strength of the optical signal.

All the fiber components named above are important in planning and

installing GPON networks.