Dr. AHhaha,
Thanks to a friend 'of ours' who walks the Last Mile Thread with us from time to time, and who for some reason has elected to remain anonymous on this topic, there is some interesting SR coverage in the April CED Magazine at:
cedmagazine.com
The above link is the second page of the article that contains the SR material. The article actually starts at:
cedmagazine.com
An excerpt is offered here for discussion.
Note that the carrier I was alluding to in the past is now mentioned in this article, although they don't offer any meaningful comments, yet.
All comments are welcome.
Regards, Frank Coluccio
----------excerpt begins:
SilkRoad's system is being tested by a number of long distance and competitive local exchange carriers, von Braun notes. He says he has talked with officials at Sprint, one of the carriers testing the system, about their experiences with the technology. "They were very impressed," he says.
So, too, are engineers at the IP-based broadband carrier Level 3 Communi-cations, according to Dataquest analyst Ken Kelly, who recently completed a report on the SilkRoad technology. While several other carriers expressed great interest in the technology, only Level 3 would allow its name to be used in Kelly's writeup, he says.
"Level 3 seems to be really high on it," Kelly adds. "I saw the system demonstrated with TV signals, and it lives up to its claims."
While the underlying physics and math are extremely difficult, the actual implementation of the technology is simple and low cost, involving use of off-the-shelf lasers and external modulators in combination with an overlay of intelligence applied to the electronic feed into the modulator. "The main drawback is it hasn't been operated in the field long enough to assure carriers they can meet (the) 'five 9s' requirements for telecommunications applications," Kelly says, in reference to the 99.999 percent reliability factor used in telephony. "So the technology will probably migrate into commercial operations for other types of applications, like data and television, to give people time to see how it performs over time."
A spokesman for Level 3 declines to comment on his firm's reported interest in the SilkRoad system, saying only, "We don't talk about our vendors, even when we actually deploy their products. So we're not going to speculate about anything we're evaluating."
As described by Rob Gorman, vice president of marketing and sales at SilkRoad, the SilkRoad technique represents a variation on coherent system technology which, in the late '80s, was seen as the means by which fiber's ultimate potential could be realized. Coherent systems, which use the frequency range and other dynamics of the optical signal itself to transmit information, proved to be too unstable to put into commercial operation and were superseded by DWDM as the next step to high capacity over fiber.
SilkRoad says it has overcome the coherent system problems through the patented ideas of its Chairman and CTO James Palmer. These concepts have to do with narrowing of laser linewidths to minimize dispersion using what is known as the "Palmer Transform" to stabilize the laser onto its optimal frequency. Equally important, the system employs new ways to modulate RF signals onto the optical stream using very high clock speeds in the 60-100 GHz range to rapidly change the light-passing characteristics of an external modulator.
In the modulation process, the system takes in all the various types of RF signals in their native formats without transposing them to a uniform format, shaving away the upper sideband and assigning a clock sampling frequency value in the lower sideband to each carrier, Gorman says. "Every (RF) signal has its own spectral output, which allows us to coherently mix them onto the beam," Gorman notes. The clock values are assigned to the beam via refractive changes in the light-transmitting properties of the external modulator, so that all the dimensional values of the photons, including space and time as well as frequency and polarity, are put to use in carrying the message, Gorman adds.
To get to this multidimensional information-carrying capability over the optical stream, Palmer reworked the original field equations of James Maxwell, which describe how electric and magnetic fields interact to impart electromagnetic energy. As explained in a paper Palmer is preparing to give at a conference in May, the resulting algorithmic solutions provide exact time dilations for each of the photonic properties within each few nanoseconds of time, allowing more signal information to be added to a given point of light than is possible with conventional two-dimensional multiplexing.
By reading the photons at the receive end in sync with the assigned sampling frequencies, the original RF signal destined for a given end device can be readily extracted from the optical signal stream, which is why signals can be "switched" by simply splitting the beam, Gorman notes.
Because the signal input is not altered from its native format in the SilkRoad system, the technology is ideally suited for the AM signaling requirements in cable, Gorman adds. Moreover, he says, the low attenuation and high linearity of the narrow linewidth beam combine to allow the system to deliver AM signals at very high carrier-to-noise levels over long distances.
"We realize this technology would be of great use to the cable industry," Gorman says. "We want to open a dialogue with cable companies as soon as possible." The company is also talking with potential manufacturing partners with the intention of maintaining full control over the design and manufacturing process, he adds.
While declining to discuss specific pricing, Gorman asserts that the SilkRoad system cost is so low in comparison to DWDM systems that its availability will "cause a serious change in the whole capital cost structure" of carriers who deploy it. "People are excited about the design implications where they don't have to replace installedinfrastructure or add a whole lot of equipment to achieve this level of performance," Gorman says. The system is indifferent to the type of fiber used, he adds. |
