Number of fibres in a fibre optic cable

[Lc85]

I have seen that there are various amounts of fibres 8,12,24 etc in fibre optic cables. Is this just one signal per fibre. So for instance an 8 fibre cable could take 8 separate signals?

Thanks

 

[davidbeach]

Fibers are used in pairs, except for the occasional unidirectional application. But there are many means for multiplexing multiple signals onto a single pair of fibers.

 

[VEBill]

"...just one signal per fibre [?]"

You must first define 'signal', then you can count them.

If you mean optical wavelength, most are single wavelength. But higher value cables (e.g. oceanic) might have multiple wavelengths.

Once you past that, it's multiple signals all the way down. Look up the ISO 7-Layer Model to grasp the typical layering concept.

The fiber that reaches my house is single wavelength. Each fiber is passively connected to as many as 16 houses. They use TDMA to share.

The cable itself along the road seems to contain 12 fibers, but this would vary. So a tiny one-quarter inch diameter cable can feed 192 houses.

 

[VEBill]

Correction or clarification: FibreOP uses two wavelengths, one for each direction.

 

[Lc85]

Thanks for the replies. So if we were to use fibre for CCTV it would be a pair of fibres for camera one, a pair of fibres for camera 2 etc?

Thanks

 

[waross]

Google multiplexing. A co-axial cable may carry hundreds of TV channels, or signals from individual cameras. A single fibre can carry many more signals than co-ax.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[VEBill]

You do whatever is cheapest and easiest. And that depends on the details.

One cannot completely avoid copper wire. Cameras obviously need power. Thus the rising popularity of Ethernet with POE.

 

[ScottyUK]

Typically most standard domestic / commercial / industrial networking applications based around Ethernet use two fibres, one in each direction. Specialised stuff as used by the telcos may use multiple wavelengths on one fibre and bi-drectional transmission on one fibre, but these are niche applications rather than mass-market.