Greetings ...

My basic understanding of coaxial cable - for the purposes of transmitting analog or digital channels - is that it has a capacity of at least 900 mhz (if not more). That would equate to 150 analog channels, or to 150 to 600 (if not more, and depending on conditions) digital channels.

Now, with regards to Fiber-Optic Cable, are we truely talking about capacity in the GHZ range? If so, how many GHZ are we dealing with? It is a personal assumption that if in fiber-optic the capacity is at least 10 GHZ (10,000 mhz), then this would equate to 1,600+ analog channels, or to 1,600 to 6,400 digital channels.

Please enlighten me - brief explanation will do.

Thanx-A-Lot, Frank-0-Video

Most coax goes up to at least 2.2GHz, with some good to 3GHz.

With an NTSC channel being 6MHz wide, that's 500 channels in a 3GHz bandwidth. If the compression scheme has 10 digital channels in one NTSC channel space, that's 5000 digital channels in that 3GHz bandwidth.

That's alot of TV to watch! ;)

Most coax goes up to at least 2.2GHz, with some good to 3GHz....;)

Yeah, but most cable systems are only built to 750 or 870 MHz...

Yeah, but most cable systems are only built to 750 or 870 MHz...

That limitation is the electronics, not the wire. :)

Yeah, but most cable systems are only built to 750 or 870 MHz...
The question was about coaxial cable, not cable TV systems.

That limitation is the electronics, not the wire. :)

I agree, but the electronics are limited by the higher loss at higher frequencies that coax exhibits. You could probably push a 20 GHz (or higher) signal through coax but the loss would be pretty high. For example see: http://www.therfc.com/attenrat.htm ...Sorry I was briefly dealing with a 'real world' application...

I agree, but the electronics are limited by the higher loss at higher frequencies that coax exhibits. You could probably push a 20 GHz (or higher) signal through coax but the loss would be pretty high. For example see: http://www.therfc.com/attenrat.htm ...Sorry I was briefly dealing with a 'real world' application...

Yes and No, with analog signal the electronic's are fine, but with a Digital 256 QAM and the haystack pattern of a digital signal it over loads with compression. Also Most of the Electronic gear would be fine with correct unity gain levels. Meaning that the hybrids in the amplifiers need to be hit the correct input levels and not too little or too much, too little would give C/N issue's and too much would affect the CSO/CTB .

All in all the best thing to happen would be to have a HFC system with Node plus one. this way you can push the frequency levels above 1ghz and also not worry about cascades of amps, cable size, connector issue's etc.

The weakest link would also be the customer's home wiring, where 90% of the problems are connector and or a cable replacement.

Sorry for the rant, But you can't really beat fiber going back to the topic of discussion.

I totally agree that fiber has a higher capacity. My mention of the electronics limitation and attenuation bears that up. The main limitations of a Coax distribution system is the cable attenuation and the inherent slope of that attenuation. CATV is only built out to 870 MHz because of the spacing of the amplifiers and the cascade depth. Modern cable design has a maximum cascade depth of 4 amplifiers and to try to push over 870 through it would require increasing that cascade, resulting in more distortion products. Node plus one is good, but requires a lot more nodes hence a lot more fiber so that really is just a 'last mile' solution and probably should be considered a Fiber system, and not truly a Coax system. FWIW Coax is commonly used to carry 2 GHz satellite signals, but in that app it typically carries a narrower band around 2 GHz and not the full 5 to 2500 MHz load.

I totally agree that fiber has a higher capacity. My mention of the electronics limitation and attenuation bears that up. The main limitations of a Coax distribution system is the cable attenuation and the inherent slope of that attenuation. CATV is only built out to 870 MHz because of the spacing of the amplifiers and the cascade depth. Modern cable design has a maximum cascade depth of 4 amplifiers and to try to push over 870 through it would require increasing that cascade, resulting in more distortion products. Node plus one is good, but requires a lot more nodes hence a lot more fiber so that really is just a 'last mile' solution and probably should be considered a Fiber system, and not truly a Coax system. FWIW Coax is commonly used to carry 2 GHz satellite signals, but in that app it typically carries a narrower band around 2 GHz and not the full 5 to 2500 MHz load.

I agree, the little secret now for everyone needing more nodes and having less fiber is CWDM, Run multiple wavelength's with MUX's in the hub and the fiber case's and it help's to double and triple the amount of node's you can have with a pair of fiber....:)

Back when I was a Fiber Hanger we used to TDR the fiber at two different wavelengths for just such a future multiplexing.