Cable Forum - View Single Post - 200M How does the Virgin Media network work?

Onramp · 17-01-2017, 18:44

It's difficult to tell but...

If the floor covers are metal with rounded corners it will be HFC. If it's been there for a while but has green or gray boxes then it's probably HFC.

If it has grey cabinets that are new-ish looking and there is no chamber cover on the floor in front of the smaller grey boxes then it is probably FTTP, otherwise it is probably HFC.

The TV works by sending the whole downstream band via an intensity modulated laser at 1550nm and there is a return path (which I think is 1610nm). The channels are QAM-16 (256?) modulated. The nodal cabinets use the intensity of the laser beam to generate an electrical signal which falls within the normal RF band for transmitting the channels. That is then sent down / received from the coaxial cables. There are a few amplifiers chained from each node which has several taps on it. Depending on the port used on the amplifier, some taps may have a higher db output than others and are for longer cable runs or otherwise require attenuation at the customer premises.

The network connection runs over bonded DOCSIS channels which are delivered via the QAM modulators. In the headend (or maybe even the nodes) they are split back into a cable modem termination system.

That's more or less all I know (or can remember from the 90s) really. Someone who actually works for the company could probably tell you more than that I'm sure.

You wouldn't be able to find out how oversubscribed the area is without trying it, I think.

17-01-2017, 18:44	#5
Onramp Inactive Join Date: Sep 2016 Posts: 210	Re: How does the Virgin Media network work? It's difficult to tell but... If the floor covers are metal with rounded corners it will be HFC. If it's been there for a while but has green or gray boxes then it's probably HFC. If it has grey cabinets that are new-ish looking and there is no chamber cover on the floor in front of the smaller grey boxes then it is probably FTTP, otherwise it is probably HFC. The TV works by sending the whole downstream band via an intensity modulated laser at 1550nm and there is a return path (which I think is 1610nm). The channels are QAM-16 (256?) modulated. The nodal cabinets use the intensity of the laser beam to generate an electrical signal which falls within the normal RF band for transmitting the channels. That is then sent down / received from the coaxial cables. There are a few amplifiers chained from each node which has several taps on it. Depending on the port used on the amplifier, some taps may have a higher db output than others and are for longer cable runs or otherwise require attenuation at the customer premises. The network connection runs over bonded DOCSIS channels which are delivered via the QAM modulators. In the headend (or maybe even the nodes) they are split back into a cable modem termination system. That's more or less all I know (or can remember from the 90s) really. Someone who actually works for the company could probably tell you more than that I'm sure. You wouldn't be able to find out how oversubscribed the area is without trying it, I think. Last edited by Onramp; 17-01-2017 at 18:52.