Sub-comms Cabinet - Components

There are a few ways this might  be done. There will be at least a pair of fibres  in optic cable, uplink and downlink, but quite likely more pairs will be run in parallel to create a 'wider'  bandwidth pipe and also to avoid single point failure. Compared to the cost of downtime, the effort of running a spare fibre and leaving it 'dark' as a fall-back is common,


The pairs of fibre  will probably terminate in a hub that has a socket for one or more  fibre optic transceivers.Nowadays these are replaceable modules, each contains a small laser for the transmitting side and a photo-diode for the receiver the smallest of these  transceivers are  commonly in 10gigabit units. For those with a bit more data to shift 16 and 32gig units exist, and  for those with very deep pockets, up to 400gig, though these are really 4 lasers and 4 receivers of different wavelengths (like colours of light)  and interface in effect much like 4 fibres in parallel, and can indeed be set up as independent or combined networks.


Then there are several variations depending on the laser wavelengths and the type of fibre that is used (single mode fibres have less dispersion over long distances but they are pricier and so are the transceivers, multi-mode fibres are more tolerant of alignment errors and so on, and the transceivers are a bit cheaper, but the range is hundreds of metres rather than km.)


The hub will take in the fibre optic interface or interfaces and redistribute data to a number of wired Ethernet ports, which will go either directly or via further hubs to split the signals further  to the outbound lines or groups of lines.

The hubs are quite likely to be programmable so they are more like 'data switches' and  can use routing rules that improve security and efficient use of the system - for example a common requirement is to  avoid data that is intended to pass between machines on the same floor to be sent and down to other floors when it does not need to be.


Mike,

mapj1‍  thanks ever so much.

So taking your answer I am going to ask a further question.

As I understand the FO will likely terminate in a hub. I will leave it there. Simple thing.

Generally speaking, from my little knowledge, in a hard wired patch panel, the patch panel racks have RJ45 sockets in the front and hard wired terminals at the back.

These hard wired terminals at the back are then connected with patch leads to the active equipment i.e. a telephone or an ethernet switch in order to provide the respective functionality of the RJ45 sockets in the front.

In a FO situation like this however what connects at the back of the patch panel in order to give the functionality on the RJ45 sockets in the front??? It may sound very silly questions. Sorry

Well each cable will go to an ethernet  hub, switch, or router  (*) in the ordinary way for building up a wired network, except that one of the bits of kit on that network will have the fibre transceivers in as well as RJ45 sockets.

M.


(*) The subtle differences are explained here 


Actually even the less sophisticated units are not really simple repeating hubs any more, and are more like switches, sorting on MAC address

the fibre optic is terminated onto a patch panel that could be SC or LC. then you use a fibre patch cord to go from the patch panel to your network switch, the switch would have a special fibre optic port for this.


your copper RJ45 cables then connect to the switch, and then to the patch panels which correspond with the sockets on the wall


terminating fibre is a specialist job


typically, you would install 8 core multimode fibre between cabinets in a situation like you describe.


you have network switches in each location, connected to each other with an RJ45 or using the cascade connection. 


you might also need to consider running copper with the fibre for other things like standard telephone lines, intercoms etc

i tried to DM you but it wouldn't work, so, in response to your DM:


almost


you have switches in the main cabinet and switches in the sub cabinet.


The fibre links the switches together 


if you have 150 sockets on the wall, typically they wont all be in use, generally, you install double the number of wall sockets than you require.


you install enough switch ports to support the equipment you are going to end up with, so if you have 50 PCs, then you would fit 3 24 port switches


not every wall socket would normally be patched in. 


dont forget that the maximum length you can run copper ethernet cable is 100m including patch leads at each end

I'd second Johno 12345s reply. 


You also get single mode (Shown as OS when you buy it) and multi mode (Shown as OM when you buy it) Fibre (One way and two way fibre)


OM4 is probably a good one for your application LC/LC.......its what we typically install in high rise offices. 


The switches etc for multi mode (OM) fibre I believe are cheaper and easier to do (Program?)  than the single mode (OS).


We don't do the IT side of it, but can do the rest of it if in London or west,  south West of London a fair way. Data and fibre.

the thing that makes a fibre single or multi-mode is the core size, the core is the region of denser glass in the centre that traps the light by internal reflection (much in the way that at the correct angles you get a reflection going from under water to air - next time you seem to have a drink in a glass, hold it up and look out through the top surface, note that from some trick angles it looks like a mirror. Cheers. ? Optic fibre is that effect rolled up into a tube so the light is trapped.


In a multimode fibre the core is larger, and the light spreads into many paths ('modes') of slightly different lengths, giving a spread in group velocity and smearing the signal timing, this really only matters over longer distances.

typically the core is 50 to 80  microns wide in a fibre that is 120um overall.


In a single mode fibre the light is more restrained,  (core between perhaps 1/10th diameter at 5 to 8 microns diameter) but the penalty is that the mechanical tolerances the fibre and its connector have to be made to are much tighter or the light misses the target altogether..

So single mode optical parts are harder to manufacture, and so cost  more. But for ultimate fast edged speed and distance it is what you need. Multi mode is slightly more tolerant of dust and alignment errors.

Thanks a lot guys

So, I had a small chat yesterday with someone who definitely has seen more than me and what he gave me as a layout for the sub comms cabinet was this (going from bottom to top of the cabinet):

The incoming FO cable will plug into a Fiber Patch Panel

From there with fiber patch leads we go into a Fiber Converter

From there with RJ45 patch leads we will daisy chain 4 x 48 ports Ethernet Switches stacked one on top of the other

From the ethernet switches with RJ45 patch leads we shall go into 7 x 24 ports Patch Panels stacked one on top of the other

From the patch panels we shall wire out to the 150 RJ45 sockets around the floors

Of course there are lots of 1U spaces left between all the above for ventilation and cable management.

All in all we are probably gonna use a 42U floor standing cabinet however THIS WAS the architecture that I was given yesterday...

So at least I have an idea

that makes perfect sense, but I always think using fibre converters instead of having a switch with a module in it is a bit amateur on a new installation. 


as with everything, there are countless ways to do it, and countless opinions.


what you suggest should be fine, assuming someone has worked out the traffic loading on the network