RE: High Density Multimode Runs BCP?

From: Thor Lancelot Simon []
Sent: Wednesday, January 26, 2005 3:17 PM
To: Hannigan, Martin;
Subject: Re: High Density Multimode Runs BCP?

> > >
> > > When running say 24-pairs of multi-mode across a
datacenter, I have
> > > considered a few solutions, but am not sure what is
> > common/best practice.
> >
> > I assume multiplexing up to 10Gb (possibly two links
thereof) and then
> > back down is cost-prohibitive? That's probably the
"best" practice.
> I think he's talking physical plant. 200m should be fine. Consult
> your equipment for power levels and support distance.

Sure -- but given the cost of the new physical plant installation he's
talking about, the fact that he seems to know the present maximum data
rate for each physical link, and so forth, I think it does
make sense to
ask the question "is the right solution to simply be more economical
with physical plant by multiplexing to a higher data rate"?

I've never used fibre ribbon, as advocated by someone else in
this thread,
and that does sound like a very clever space- and possibly cost-saving
solution to the puzzle. But even so, spending tens of thousands of
dollars to carry 24 discrete physical links hundreds of
meters across a

Tens of thousands? 24 strand x 100' @ $5 = $500. Fusion splice
is $25 per splice per strand including termination. The 100m
patch chords are $100.00. It's cheaper to bundle and splice.

How much does the mux cost?

datacenter, each at what is, these days, not a particularly high data
rate, may not be the best choice. There may well be some
question about
at which layer it makes sense to aggregate the links -- but to me, the
question "is it really the best choice of design constraints to take
aggregation/multiplexing off the table" is a very substantial one here
and not profitably avoided.

Fiber ribbon doesn't "fit" in any long distance (+7') distribution
system, rich or poor, that I'm aware of. Racks, cabinets, et. al.
are not very conducive to it. The only application I've seen was
IBM fiber channel.

Datacenters are sometimes permanent facilities and it's better,
IMHO, to make things more permanent with cross connect than
aggregation. It enables you to make your cabinet cabling and
your termination area cabling almost permanent and maintenance
free - as well as giving you test,add, move, and drop. It's more
cable, but less equipment to maintain, support, and reduces
failure points. It enhances security as well. You can't open
the cabinet and just jack something in. You have to provision
behind the locked term area.

I'd love to hear about a positive experience using ribbon cable
inside a datacenter.

Hi, Thor

We used it to create zone distribution points throughout our datacenter's
which ran back to a central distribution point. This solution has been
in place for almost 4 years. We have 10Gb SM ethernet links traversing
the datacenter which link to the campus distribution center.

The only downsides we have experienced are

1 - Lead time in getting the component parts

2 - easiliy damaged by careless contractors

3 - somewhat higher than normal back reflection
    on poor terminations

                            Scott C. McGrath