Does "maximum value" in your opinion mean a positive (+) voltage, specifically, with respect to neutral, or ground? Or does it mean the highest absolute voltage irrespective of polarity? I would tend to think that neither is true where determining the logical one (1) state is concerned, if judged purely on their face values.
You seem to imply that logical ones should be of a positive polarity or maximum value. In most electrical coding conventions of the types we've been discussing, it's usually the negativemost voltage that represents the logical one (1). Unless we get into bipolar return to zero with 50% duty cycle schemes, or those which are transition-dependent, or use Manchester (-like) coding. But hey! You are right: What do these issues and arcane electrical principles have to do with solitons?
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re: Solitons, I'm still waiting for some enlightenment from you and others here, since I'm no soliton expert. In the meantime, here's an article about a startup in France which purports to deliver DWDM hardware using soliton technology, soon. Here, reference is made to shaping solitons for use on DWDM, which was something I meant to ask you about. You stated that RZ would be the only scheme used for soliton transmission. Can you go a little deeper, there? Why is that? There are papers circulating in the IEEE now concerning the pluses and minuses of RZ vs NRZ in DWDMs. Although, they don't address soliton technology, I should add.
========from Lightwave:
October, 1999
Startup poised to bring soliton DWDM
systems to market by mid-2000
By Robert Pease
For more than six years, a team of engineers from Cnet, the
research and development arm of France Telecom, have
been working on soliton technologies for long-haul
communications. One product of the team's labors is the
formation a new company called Algety Telecom (Lannion,
France), which plans to bring soliton dense
wavelength-division multiplexing (DWDM) systems, a new
breed of optical transmission equipment, to market by
mid-2000.
Cnet is responsible for numerous pioneering developments in
soliton technology, including the current record for
terrestrial soliton transmission of 1 Tbit/sec over a distance
of 1000 km. Algety, incorporated in France during the
second quarter of 1999, negotiated with Cnet to gain the
technology, patents, and know-how necessary to continue
the advancement of soliton communications.
Algety is developing a new generation of solitons for DWDM
and Synchronous Optical Network/Synchronous Digital
Hierarchy (SONET/SDH) long-haul transmission. The
company's objective is to enable carriers to increase the
distance between regeneration and amplification sites and
improve the overall spectral efficiency of their networks.
According to Algety, carriers could eliminate millions of
dollars in equipment from every link, decreasing long-haul
costs typically by a factor of two or even three.
"With traditional techniques, you have to regenerate the
signal every 300 to 400 km," says Jerome Faul, managing
director at Algety. "With solitons, you only have to
regenerate every 1000 to 2000 km. So you can increase
the distance between two regenerators and save a lot of
money. It's perfectly suited for large countries such as the
United States, where you have miles and miles between
cities. It's a technology designed for long-haul--the longer,
the better."
A soliton is a natural phenomenon dating back to 1834,
when Scotland's John Scott Russel made an observation
while riding horseback along a canal. Russel noticed that
after a barge had come to a sudden halt, a big solitary
wave continued to travel without any apparent shape
deformation or speed variation. He followed the wave more
than 6 mi and reported his observation in 1844. Some 60
years later, mathematicians were able to unravel much of
the mystery behind the phenomenon.
By 1973, Bell Laboratories (Murray Hill, NJ) discovered that
solitons could be produced in optical fiber by sufficiently
intense pulses of light and that the phenomenon could
overcome the problem of dispersion (or the spreading of a
light pulse). This discovery led to a renewed interest in
solitons as a means to increase transmission distances and
bandwidth capacity--until DWDM reared its head in the
telecommunications realm.
Since the mid-'80s, the development of DWDM technology
has relegated soliton transmission research to a lower
profile. But as limitations in DWDM transmission have
appeared, researchers--particularly in Europe--have
continued to work on perfecting soliton technology.
Algety has embraced DWDM technology to combine the
best of both worlds. The company plans to introduce
products incorporating advanced DWDM technology to
maximize available fiber bandwidth and soliton technology
to increase the speed per channel.
"Our products will include high-speed multiplexers," says
Faul. "Each input is shaped like a soliton and multiplexed
with all the different inputs to send on a single fiber. This is
where we can achieve the high capacities. DWDM
technology is new in the soliton arena, and up to now,
nobody else has successfully mixed soliton technology and
DWDM technology."
According to Faul, carriers can keep their existing
fiber-network infrastructure and merely change equipment
at the ends of the fiber. Moving to higher capacities with
traditional methods has meant that carriers had to reduce
transmission distances between regenerators.
"[Soliton transmission] allows them to keep their existing
infrastructure and replace their old equipment with ours,"
says Faul. "So in the same step, they can upgrade the
network in terms of capacity and keep the infrastructure in
terms of transmission distance. There are also physical
problems, such as dispersion, in some existing fibers that
occur when increasing capacities. A key feature of the new
soliton products will be the ability to manage those
problems very well."
Algety plans to have prototype products available for
testing in the laboratories by year-end.
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