NBN Overview

The Mandate

The National Broadband Network (NBN) is a national wholesale-only, open-access data network that was under development in Australia until the election in September 2013.  This meant that the company created to build and run the network (NBN Co) will not provide retail services to individuals, businesses or other institutions.  They will only provide services to so called RSPs (Retail Service providers, similar to the current ISPs) who will then provide the retail services.

The NBN Co was  instructed by the previous  Government to make a fibre connection available to 93% of Australian premises. The remaining 7% premises must get connections provided by  fixed-wireless or satellite.  In this web site we  will only discuss the fibre portion of the NBN.

NBN Footprint

The NBN fibre primarily consist of what in communications jargon is described as “the last mile”.  This means the links from the nearest  “Exchange” to individual premises served by that exchange.  In NBN terminology, an exchange is called a “FAN’, or Fibre Access Node.  These FANs will mostly be located within existing Telstra Exchanges (ESAs) but there will be fewer FANs than ESAs. The approximate numbers are about 980 planned FANs against more than 5000 Exchanges.  This is driven both by technology differences (greater fibre length for NBN network) and the fact that NBN Co’s fibre network will cover 93 percent of premises, which overlays approximately 1,900 of today’s ESAs.

Some FANs will also serve as Points of Interconnect (POIs). There will be 121 POIs.   This is where NBN Co hands over traffic from its network to service providers.   NBN Co is constructing a Transit Network with connections from the Fibre Access Nodes to the Points of Interconnect incorporating transmission rings. In addition, the POIs themselves are interconnected in a ring right around Australia.  These rings provide greater resiliency, ensuring that if a single link in a loop is cut then services remain in operation.

The December 2010 NBN Co  Corporate plan  estimates are that the “last mile” fibre network will require 181,00km of fibre and the Transit Network 57,000km.

The Distribution Fibre Network (DFN)


Fibre Serving Area Module (typically one suburb)

Fibre Serving Area Module (typically one suburb)

Typically, each suburb is connected  to the FAN (Exchange)  by a ring of up to 16 Fibre Distribution Hubs (FDH).  Such a configuration is called a Fiber Serving Area Module (FSAM).

The  ring consists of up to 16 HUBs which are all connected to fibre that originates and ends at the FAN as illustrated in the picture above. This ring allocation provides an alternate pathway for end-user connectivity and allows for temporary service restoration when required. In the event of a serious service impacting event (e.g. Cable cut etc.,) the services that are connected to the affected side can be manually re-patched at the FDH and FAN site.

Fibre Distribution Hub (FDH)

A FDH cabinet - H 111cm, W 54cm D 34cm

A FDH cabinet – H 111cm, W 54cm D 34cm

The FDH is an environmentally secure passive device installed on  street frontages and serves as a centralized splitter location.  Being passive means that the device requires no electrical power. In fact, the only power needed in the Distributed Network is at the FAN and at the user premises.

The splitter modules housed within the FDH provide a one-to-many relationship between the in-coming DFN and the out-going  fibres.  In the current NBN design, the splitter modules in the FDH splits one incoming fibre into 32 separate fibres, each of which serves one premise. One FDH will serve about 200 premises.


Local Fibre Network (LFN)

Inside of FDH

Inside of FDH

The LFN consists of the part of the network from the Fibre Distribution Hub (FDH) down each street, typically serving between 50 and 200 premises each. The Local Fibre Network (LFN) is installed from the FDH to the end-user premises in a star topology. LFN cables are typically smaller fibre count cables, ranging between 72 and 288 fibre counts, and are installed in the aerial corridor and underground pathways typically alongside property boundary street frontages. The LFN cables are presented at the FDH on a connector array to facilitate connection to the upstream DFN either via a splitter or direct connection. Inside the FDH each of the colored strands represents one connection to a premise.

Cable in pit

Cable in pit

Inside the thick cable in the pit shown on the right there are many individual fibre-optic strands. The black box attached to the cable splits them out, allowing individual premises to be connected.




PCD on outside of premise

PCD on outside of premise

A Premises Connection Device (PCD) will be installed on the outside of the premises and the cable left coiled within it to be connected to a Network Termination Device (NTD) at a later date. Or, if the NTD is installed at the same time, the drop cable will be connected immediately. Where there is a PCD and an NTD, there will be a fibre cable installed between the NTD location and the PCD.


Inside PCD
Inside PCD


The fibre optic cable is coiled up inside the Premises Connection Device (PCD) and connected to a “fibre patch lead” which runs through to the inside of the house.




TCU mounted inside house
NTD mounted inside house


The NBN box (NTD) is mounted on a wall plate inside the house at a location of your choice (with some limits).  This is the fibre equivalent of a modem. The patch fibre from the PCD is connected to the NTD.




Back of TCU (aka NTD)

Back of NTD


This is the rear of the NBN Box. On the left hand side, the two “UNI-V” ports are voice telephony ports, into which you can plug any standard telephone. The four “UNI-D” ports to the right provide Internet data. Each of the four ports can be used for a separate internet service. The fibre-optic cable is installed in the hole at the right denoted by the laser warning symbol.



  1. There will be no charge to the user for the PCD or NTD.  If you require installion of the NTD in a location that is more difficult than normal, you may be charged for this. The assessment of what constitutes a “more difficult” installation will be done by the installer.  You may also be charged for the NTD installation depending on your selected ISP.
  2. This site is not sponsered or approved by the NBN Co in any way. For the exact details about the terms of your installation, you should contact the NBN Co.