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Originally Posted by ianathuth
NTL cable provides both TV and broadband. This is carried over fibre and coax. Where does the changeover from fibre to caox take place and what hardware is used to make this transition? What is the maximum length of coax that can be used and is this maximum the same for TV and broadband?
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A simple answer to your question is the fibre ends at the Nodal cabinet, the nodal cabinet usually feeds an area passing an average of 500 Homes. The Nodal cabinet then uses coax in both direction (forward and return path) to feed Distribution Amplifier cabinets and Distribution points.
The nodal amplifier contains an optical receiver that converts the optical signal back to an RF electrical signal that is the same as the one leaving the headend, it also contains an optical transmitter to take the return path RF from your set-top or cable modem and convert it into an optical signal to send back to the ubr.
One area thats probably not realised by many is between the headend and the node, is a hubsite. This is a building containing racks of equipment, and the optical forward signal in the case of TV is converted from optical to RF, and then back to optical to feed the nodes. The return path signals are also converted back to RF at the hubsite and split to various equipment for processing. (ubr, intersect etc) some frequencies/services are fed to another optical transmitter to be yet again converted and sent back to the headend.
So to put it into context the RF Television signals, both analogue and digital leaving the headend modulators undergo the following before they reach to customer.
RF fed to headend optical transmitter, down a bibre to the hubsite. Fed to an optical receiver for conversion back to RF, this signal is then fed to an optical transmitter and fed via splitters to individual nodes. The node then converts this optical signal back to RF to be distributed via DA/DP cabinets.
The return path/US is just the reverse process..................
