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Tony Li
Tony Li
12/5/2012 | 2:18:15 AM
re: Hollow Fiber: No Pipe Dream

Low loss is a fine thing, but what about its dispersion properties?

Tony
arch_1
arch_1
12/5/2012 | 2:18:14 AM
re: Hollow Fiber: No Pipe Dream
What is the propagation speed in hollow fiber? the propagation speed is usually the speed of light in the medium.

In a vacuum. signals propagate at the speed of light C, which is 300Mm/sec.

In any other medium, signals propagate at the speed of light in that medium. This is C/I, where I is the index of refraction of the medium. For traditional fiber, I=1.5 or thereabouts, so signals propagate at 200Mm/sec in a standard fiber.

New York to L.A. is roughly 5Mm direct, or 6Mm fiber distance. This 30Ms for solid-core fiber, and 20ms in a vaccum. Air has an index of refraction that is close to 1.

If hollow fiber has an effective index of refraction near 1, then the signals are roughly half again as fast as in standard fiber.

Does anyone care? Well, current core routers impose a switching delay of <1ms, and (apparently) customers are concerned about differences in switching delay measured in the microseconds. From this I conclude that an improvement in the propagaton delay of ten milliseconds is a very big deal.
Tony Li
Tony Li
12/5/2012 | 2:18:11 AM
re: Hollow Fiber: No Pipe Dream

Actually, you should conclude that the customers have been speaking to switch salespeople. ;-)

Tony
ehwhatsupdoc
ehwhatsupdoc
12/5/2012 | 2:18:10 AM
re: Hollow Fiber: No Pipe Dream
Tony, are you leaving Procket? If so, when's your last day?

thanks...
Tony Li
Tony Li
12/5/2012 | 2:18:09 AM
re: Hollow Fiber: No Pipe Dream

Sorry, you're stuck with me. Until you hit 'ignore author' at least... ;-)

Tony
Larry, Monkey
Larry, Monkey
12/5/2012 | 2:18:07 AM
re: Hollow Fiber: No Pipe Dream
Probably, those messages are still on the board attached to the story where it originally appeared, here:

http://www.lightreading.com/do...

Sorry for the confusion.

Probably Copy Chief
probably
probably
12/5/2012 | 2:18:07 AM
re: Hollow Fiber: No Pipe Dream
What happened to the other messages posted over a week ago about this topic? They have strangely disappeared (I haven't ignored the authors: I was one!).
whyiswhy
whyiswhy
12/5/2012 | 2:18:05 AM
re: Hollow Fiber: No Pipe Dream
Hollow fiber was originally touted as the savior to fiber...as it was generally thought that removing the core would remove the loss-inducing element.

BUZZZZ!

Removing the core not only increased the loss by (was two, is now one) order of magnitude, it induced very high non-linearities.

This technology needs to go back onto the lab curiosity shelf until they get the loss down to conventional fiber. Then the other "features" might be of use in telecommunication. Until then, it might find application in fiber doublers, if that small issue of mode diameter-differences can be worked out. There it has to compete with and PPxx in both bulk and thin film-form.

-Why
dwdm2
dwdm2
12/5/2012 | 2:18:03 AM
re: Hollow Fiber: No Pipe Dream
arch_1, your technical analysis is perhaps OK for the propagation speed; 10 ms improvement between NY and L.A. is appreciable...only if there is no adverse side effect.

Does anyone know how does the loss curve of the hollow fiber compare to that for single-mode fiber? Any data will be appreciated.

What about the cost factor? Any thoughts?

Thanks
beowulf888
beowulf888
12/5/2012 | 2:17:59 AM
re: Hollow Fiber: No Pipe Dream
Pauline, I'm confused. You state...

"After decades of development, the loss of optical fiber has settled at a figure of around 0.2 dB per kilometer (dB/km). The very best commercially available fiber is from Sumitomo Electric Industries Ltd., with a loss of just 0.151 dB/km."

Then 3 paragraphs later, you state...

"Naturally, BlazePhotonics believes that ultra-low-loss hollow fiber is a viable proposition and says its latest results point the way. The new results it's reported are losses of 1.7 dB/km, which is a significant improvement over the previous best of 13 dB/km, which was set by Corning..."

Sounds like you're off an order magnitude in one of those paragraphs.

--Beo
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