Fibre Broadband

Fibre broadband delivers superfast Internet and TV services to the home...

A small Huawei fibre broadband street cabinet in Southend © LSA November 2012.

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From here to Infinity

From the appearance of home computers in the 1980s which used 'dial-up' modems to 'bulletin boards', the available line speeds (over copper) gradually increased from (typically) 9.6 kb/s up to a surprising 8 Mb/s (max), as fast access to the Internet became a necessity.

The speed of broadband drops off very quickly as the line distance from the telephone exchange increases. To improve line speeds, fibre optic cables are laid from the telephone exchange to a new cabinet which is situated close to the subscribers premises. Thus, 'Fibre To The Cabinet' (FTTP) can deliver speeds of up to 40 Mb/s under ideal conditions. This product was marketed by BT as Infinity. A later upgrade to the technology allowed speeds of up to 80 Mb/s (Infinity 2).

How it works

A normal broadband connection via an ADSL superimposes the broadband signal over the entire PSTN line and uses filters at each end to separate the broadband signal from the telephone speech and signalling. With FTTC, the broadband signal is added to the subscriber's line (via filters) at the local street cabinet (Primary Connection Point). A filter in the home Linebox separates the telephone part of the circuit.

	The subscriber's line (A & B pair) terminates on the NTE5 which contains the bell capacitor. The service specific face plate (ssfp) contains the broadband filter. The final part is the telephone socket with idc connectors for extension telephone sockets (if required). A typical Openreach NTE5 for use with fibre broadband © LSA October 2014.

ADSL is an Aysmmetric Digital Subscriber Line. PSTN is the Public Switched Telephone Network.

	PCP on left and large Huawei DSLAM cabinet on right. PCP and Huawei DSLAM cabinets © LSA November 2012.

The Infinity subscriber's line is jumpered from the PCP through to the Huawei DSLAM (Digital Subscriber Line Analogue Multiplexer) to superimpose the broadband signal onto the line. The DSLAM cabinet is connected to the Broadband backhaul (at the telephone exchange) via a new dedicated fibre optic cable network.

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