Marty, This piece made me wonder if WDM will decrease the need for encoding? Just a little or a lot?
multichannel.com
Translation Please: Dense-Wave-Division What?
Amid the blur of announcements coinciding with last month's Western Show
was a flurry of news about advancements in a terrific example of the
techno-gibberish name game: dense-wave-division multiplexing, or DWDM.
We all just have to accept the fact that lightwave technology almost
always comes with a daunting moniker. History supports the premise: A
few years ago, it was "erbium-doped fiber amplifiers," because whoever
named the technology thought that it was important to include the name
of the rare earth ion that worked to send light signals further.
Then, there was that pesky "polarization modal dispersion" problem,
which basically meant that the actual piece of fiber was a bit more oval
than it was round, which created problems.
This is my long way of saying: Fear not. Despite its intimidating name,
DWDM is not all that hard to grasp.
In short form (and, as always, with apologies to the purists), DWDM is a
way to send more signals much further over the same single strand of
fiber.
It's not a new concept, either. Long-distance carriers have been using
WDM gear for years to send phone signals over their optical networks;
two years ago, BellSouth Corp. bought WDM equipment from Pirelli so that
it could jam some 130,000 simultaneous voice channels onto a strand of
fiber and send it about 310 miles.
The more recent news is from Scientific-Atlanta Inc. and Synchronous
Communications, both of which trotted out new DWDM gear last month.
From a technology standpoint, Synchronous' news was perhaps the most
startling, because it crams signals into 32 wavelengths (loose
translation: 32 different colors of light) that travel on the same,
1550-nanometer strand of fiber.
S-A's solution crams signals into eight wavelengths (or eight different
colors of light), which can go a distance of about 100 miles on a single
piece of 1550-nm fiber.
At the moment, these DWDM moves mostly apply to the regional backbone,
and they will be particularly useful in cases where operators are short
on fiber, but where they had the foresight a few years ago to put in at
least one strand of 1550-nm fiber.
The vendors are saying that generally speaking, DWDM usage can shave
about 50 percent off the cost of the alternative, which is to install
multiple fibers to carry signals.
But despite its clunky name (S-A's press materials recommend the use of
yttrium/erbium-doped fiber amplifiers with its DWDM gear: Yikes!), this
looks like one of those technologies that is finally coming down the
cost curve enough to be of real benefit --especially for headend
elimination and regional interconnects.
Diversion: For avid Gilder readers; His most recent newsletter is co-authored with a guy named David Isenberg, and has a lot of qoutes from his "concussive essay",(Nothing to do with CUBE), but if you want
to read it I found a copy at;
people.qualcomm.com
Yes, CUBE is still on his ascendant technology list. |
