Is An All-Fiber LAN
Really Cheaper Than
Copper?
The answer, surprisingly, may be "yes" for new construction and major
renovations. I know, "everybody knows fiber is too expensive," but that
turns out to be a generalization that is out of date and comes from a
"apples-to-oranges" comparison that favors the traditional copper architecture.
This copper LAN layout as described in the EIA/TIA 568 standard
(shown on the left of the drawing), follows traditional telephone system
designs from decades ago. It divides the LAN into "horizontal" cabling no longer
than 90 meters connecting the desktop and a hub in a wiring closet. The
horizontal distance limitation is the performance of the UTP cables. Every
closet has a hub, which requires space, power, UPS and installation. Maybe even
AC! Most closets have punchdowns, patchpanels and other passive hardware too.
The "horizontal" cabling connects to a "backbone," which by virtue of
bandwidth and distance requirements, is mostly fiber optics already. The
backbone connects all the hubs to a central communications facility, usually
called a main telecom closet, where the complete LAN is managed.
When the "copperheads" (I refuse to divulge the source of that term!) compare
fiber-to-the-desk (FTTD) to copper, they show that a horizontal fiber cable
plant may only be a few dollars more than Cat 5 UTP, but the network electronics
for horizontal fiber cost a lot more, making fiber uneconomical.
That is a totally erroneous comparison, because with fiber you aren't limited
to 90 meters. With fiber, you don't need horizontal and backbone links, you
don't even need a telecom closet! You just need one link, a pair of fibers
straight from the desktop to the main telecom closet (shown on the right of our
drawing) You don't need a hub, power and backup power for the hub, racks and
space for all that or installation and maintenance labor. At most, with fiber
you have an intermediate passive patch panel to connect desktop cables to the
backbone cable and some extra (cheap!) fibers in the backbone cables.
So how much extra does the copper network cost? Different
installations will yield different numbers, but in realistic comparisons, an
all-fiber network usually comes out equal or cheaper!
Sound too good to be true? One of the most sophisticated LAN installations
anywhere, the Getty Museum in Los Angeles, saved almost $4,000,000 by going to
an all-fiber network. That's correct - FOUR MILLION DOLLARS! According to a
Corning presentation at a recent 3M seminar, with UTP, they would have had to
build 55 telecom closets in the museum, with hubs, power, etc. at a cost of
$73,000 per closet. With an all-fiber network, they needed only one closet,
saving an incredible amount of money (not to mention floor space for artwork,
researchers, etc.)
Another big issue in LANs is reliability. We all know about fiber's immunity
to electrical noise. But with an all-fiber network, you have only half as many
electronic parts to worry about, because you get rid of all the hubs. That means
there are only half as many pieces of equipment to fail, so the all-fiber
network should be twice as reliable. And since all the master electronics is in
one space, it's much easier to manage and troubleshoot.
Now we have established fiber's economic superiority, we don't even have to
point out how fiber gives you a big advantage in upgrading too, instead of the
relentless push to upgrade UTP installations every couple of years(but we did
anyway!)
For all the 568 standards "wonks", the EIA/TIA 568 committee has recently
issued TSB-72 which recognizes a centralized fiber optic network solution. It
offers a simple, reasonable solution for an all-fiber network if you ignore the
fact that they just don't seem to understand that fiber doesn't need the
"horizontal" and "backbone" nomenclature. But you can tell you customers that an
all-fiber network meets the "568" standard. And it may save them lots of
money!
PS: Another advantage of fiber will be the new generation fiber optic
connectors. They are smaller than the current ST and SC connectors and
several of these connectors offer the potential to greatly reduce the cost of
fiber optic installations. They are so small, hardly bigger than the cable
itself, it may prove feasible to install pre-terminated cables rather than field
terminate. And that may be even more cost effective. We'll visit that option in
a future column.
© 1999, fotec, inc.
information courtesy of Fotec
Inc and Cable U
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