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New Fiber Development
Maaaac writes "Just read this on GMSV: 'British researchers are developing a new kind of optical fiber that could surpass the known data transmission limitations of fiber. Augmented with a pattern of microscopic air holes that runs their entire length, these aptly-named holey fibers have a variety of surprising optical properties, not the least of which is single mode operation at all wavelengths and the ability to withstand the transmission of huge amounts of energy or data. To produce the fibers, researchers aligned an array of thin glass tubes, melted them together, and then stretched them to make a single fiber several kilometers long and about 125 microns across. While it's previously been suggested that such fibers would be predominantly used to transmit power -- or even matter -- their data transmission capabilities could be instrumental to the development of optical computers.' Now if only they would run this to my curb..."
It allows multiple frequencies to pass as if they were going down a mono-modal fibre.
It changes the refractive index without requiring strange doping of the glass.
More energy can be pumped down as the waves spread out. This means that fewer repeaters are required.
New Scientist had a good article on these fibres a year or so ago, and I talked to some of the researchers at the Royal Society.
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Well, I'm not the telco, so I can't give an offical confermation, but my understanding is there are miles of unused dark fiber.
The reason we don't use it is it doesn't go anywhere we need more capacity. The most expensive part of running fiber is the labor. So when they hire someone to run a fiber line between two offices they don't put in four pieces of fiber (Assuming they need 4), they put in a hundred. If the workers accidently break on fibre line (or there is a defect) there are still 99 potentially good lines to choose from. This leaves a lot of fiber that isn't in use because it is unneeded. If tommorow the telco decides they need more capacity it is very simple for them to add it, just use anouther line.
In theory it is possibal to lease one of these lines and have your own equipment on each end. Problem is they run from telco office to telco office, not to your neighborhood.
Basicly there is a lot of dark fiber because it doesn't cost much to put it in dark fiber so they add redundant capacity. they don't use it because they have no data to put down those lines.
I have read something similar. The idea is that companies are laying fiber, but not lighting it up until bandwidth demands necessitate it. They are merely planning on having the infrastructure in place for when they do need it. I remember reading about it in Canadian Business Magazine, the same issue I first read about FutureWay. I think it was in this article. I particularly love the Gates reference at the end:)
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Pilchie
If it is a L3 backup then it is connected to an IP router and some sort of routing info is going over it. If it is a L2 backup it is connected to an ATM or Frame Relay switch and some sort of L2 protocall is running over it exchanging whatever it exchanges. If it is a L1 backup it is dark until it is needed.
However not all backup circuits are dedicated. People will pay for a circuit that isn't there all the time. They don't pay nearly as much as they pay for one that is there (almost) all the time.
Lastly not all that dark fibre is in use. It is very very expensave to dig up ground and run cable (or fibre), copper is cheep, and fibre is way more expensave then copper, but a lot cheeper then putting it in the ground. So when you get the right to lay fibre and the equiptmenr lined up, and the folks there digging (or running the flow mole) you put way way more fibre then you need.
Sometimes that way more then you need is more then anyone needs. A fibre from DC to NY is going to have a lot of demand. One from Ohio to, well, some other part of Ohio may not get nearly enough demand to fill it. Since it only costs (say) 20% more to get 5000% bandwidth, it is worth it on the off chance that those two remote parts of Ohio become boom towns sometime.
Other fibre may be held back to keep prices up, but I expect that is rare (I have no evidence one way or another). Some there may even be demand for, but nobody realises it is cheep enough, or they can't find the right part of the right compony to buy it from. Big busness may have effencies of scale, but they also have ineffencies of scale.
Talk to someone from UUNET. They'll tell you about trying to double capacity every 6 months in order to keep up with the demand. It won't be long before today's "fat honkin' pipes" are tomorrow's "2400 baud modem line".
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Imagine if you had some way (think nanotech or fast STM) to arrange the atoms at the other end into molecules, and from there up. Matter transporter/3d Fax/replicator/world's best RPD station? If you could deconstruct the other end, perhaps wired teleportation. All of this is blue sky stuff, but remember you heard it here first, and these ideas are public and prior art (ok, I am sure someone else has thought of them in relation to this fiber, perhaps)...
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Along Railroad rights of way. The RRs run between cities, they own the land, and many of them laid fiber when they laid wires for the control signals for the signals. Sprint got its name because it was started by the Southern Pacific railroad. Lots of fiber next to their tracks. These days lots of fiber is laid next interstate highways.
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Will someone explain where the holes are and their affects on light in a clearer manner?
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Actually, you are right. The important thing to remember is that typically different modes in an optical fiber have different optical path lengths and this can limit the speed you can transit information.
... The typical 1.55 um wavelength of operation for a fiber was not picked out of a hat.
There are graded index optical fibers such that the optical path length of modes launched in an arbitrary (confined) direction is equal within in the limits of ray-tracing theory (which may or may not be appropriate for a given fiber). In fact, calculating the grading profile to equalize the optical path length is a standard textbook problem (at least in graduate courses).
As to the earlier comment stating you can not do much about other sources of dispersion in a fiber:
That is not quite correct. Carefully picking the wavelength, modulation scheme, fiber materials, fiber grading and what not can be used to play tradeoff games between attenuation, dispersion, bandwidth
Also, non-linear crystals can be used to play games with the spectral characteristics of a signal in an optical fiber to invert the dispersion. (By the way, similar spectral tricks are played in the new-fangled 10^18 W/cm^2 intensity desktop pulsed lasers.)
The reason all that "dark" fiber is not being used is because, as the other replier mentioned, the cost to run extra, unneeded fiber is minimal. The cost to "light it up", however, is NOT inconsequential.
What this means to you and me is that there's a whole lot of capacity available for future expansion, as soon as someone or some organization/business/etc. is willing to pay for the bandwidth.
Supply and demand. Easy-peasy.
I've heard that there are miles and miles of "dark fiber" in the US, fiber that hasn't been used yet.
If this is true, why aren't we using it? Can anyone confirm or deny this?
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Anybody seconds my proposal?Now, I'm not a person with hands-on experience, and really the only reason I'm posting is to get someone like that to reply. I'm genuinely curious about this. Anyway, my opinion:
We have some pretty fat honkin' pipes.... relative to the end users. They're "holding up" network speeds in more ways than one. When someone gets broadband, trust me, they're going to end up using all of it.
I don't think pipes today are capable of handling a faster last mile. Fiber to the home nothing, let's just go with 30% of internet users getting cable instead of what is it now, 5% I think? Companies today are loathe to go the last mile because the last mile is costly, and the current networks would need a big-ass overhaul. That's a lot of money. They would end up having to eat it or pass the cost on to consumers. Both situations don't really look good.
So to anyone reading who perhaps could answer on the basis of more than an opinion, how ready is the internet for a faster last mile? And then anyone else, how do you suppose we get that to happen? I'm not but so sure 10 years from now modems will still be prominent.
And what would you do with all this bandwidth? Download ISO images at 30 K/sec because the mirrors are swamped? Read Slashdot, slowly, because its all in Perl? Try and pull up pages on TomsHardware, and lag because the web bugs and banner ads come from a dozen over-subscribed servers? 3MBit cable access isn't even that fast sometimes. Speeding up the last mile will only swamp the NAPs more than they are now. It's all a chain, as strong as its weakest link.
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Theoretically, yes, but the path length for each mode doesn't vary much, only by roughly 0.01% - 0.2% between successive modes. On the other hand, a difference of 0.015 between the indices of refraction of the core and cladding creates speed differences of around 2000km/sec between the two materials, or about 1% for standard glass. Higher modes have a longer path difference, but they also penetrate further into the cladding and get sped up more. The effect of the speedup in the cladding is more pronounced than the effect of path length, so higher modes reach the end faster.
In an optical fiber, light rays traveling through the core can bounce off of the outer boundary between the cladding (lower index of refraction) and the core via total internal reflection. However, interference only allows rays at certain angles with respect to the fiber propagate. Each of these valid ray directions represents a mode.
Single mode operation means only the axial mode, where the ray travels straight down the core, is valid. The reason single mode operation is desired is because the higher modes do penetrate into the lower-index cladding where the speed of light is higher when they reflect off of it, which causes the higher-index modes to propagate faster than lower modes. Basically, if you fire a very sharp pulse of light of all modes into an optical fiber, the modes will all reach the other end of the fiber at different times. Since your sharp impulse has been spread over time, there is a limit to how many different pulses can be resolved over a certain period of time. Single mode operation means that there are no higher modes and hence less spread and higher bandwidth. (There are other causes of spread, but not much can be done about most of them).
Because, that would require forethought, planning, and a willingness to spend more money now to save money later.
It would be like the Gas company asking the Water company if they would like access to the hole they are currently digging up in the middle of a main road to save the effort of them digging it up for their own needs later *sigh*
They were meant to try this in the UK within the last 5 years or so, but it's never happened. This is why ever road and pavement is in such a mess.
Actually, they have been in much more of a mess since we allowed cable companies to dig the entire country up for Cable TV & phones. At least BT never left the place in such a state.
Experiments also indicate that microstructured fibres like holey fibres could be used to guide atoms. A fibre is made with four holes in a square and a central hole. A wire is inserted in each of the four outer holes and a current passed through it. This creates a magnetic field that can guide atoms through the central channel. Proof of principle experiments have shown that this is possible, but research here is only just beginning.
Even though this isn't about moving huge amounts of stuff around, moving individual atoms is 'matter transmission'. This could be interesting if some of the quantum state of the atom is preserved - maybe use it for information storage?
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There is more fiber put down at the backbone level than anyone needs or is willing to use at this point. Why? Light the fiber, create more supply, LOWER THE PRICE. That, along with increasingly strategic peering agreements, are measures in place to keep the price of transmitting a bit from falling to zero, which they certainly would if the fiber was lit up at once. While zero is a nice sounding number to the consumer, it stinks if you are Qwest or UUNet.
Pricing is vicious right now. None of the vendors are going to free up extra supply in a tight economy, it would drive the price down even lower and they would collapse. Add on the peering agreements which control the competition, and Yes Virginia, the internet backbone is a cartel operation.
Content distributors no longer need to clog the NAP to get you want you want, many are using caching to deposit the information near or at your ISP. Sure for dynamic sites this can't be done completely, but you can sure as hell cache almost all of the images, and more of the content than you might think. How much of the bits on this page are really dynamic? I bet the images represent a larger chunk of bits.
Because, that would require forethought, planning, and a willingness to spend more money now to save money later.
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Because the size and positioning of the holes can be specified, the fibre can be designed to confine the light it is sending to a small central region of, say, a micron square, or a "big" region of several thousand square microns. If this central region is small, it is possible to operate an optical switch using very low light intensities, which is important for the future development of optical computers. (Indeed, optical switching has recently been demonstrated in a holey fibre by researchers at Southampton University.) In a "large mode" holey fibre, the cable can send lots of power, which makes these fibres useful for applications such as laser welding and machining, as well as the development of high-power fibre lasers. Being able to tailor the way light is guided by a holey fibre could revolutionise the way data is transmitted and there are likely to be many other exciting applications which have yet to be discovered
The optical computing aspects are exciting, however.
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Big whoop. We already have some pretty fat honkin' pipes. The real hold up and cost is not the fiber or the fiber's capabilities, it's the machines at the ends of the fiber. Certainly, when laying fiber you want to lay the best fiber you can for future needs. But even now most fiber is enormously underutilized. Most high speed connections (faster than oh about OC-3) currently requires multiple computers to handle the bandwidth. And it takes even more equipment to bridge between the fiber and all the other networks (most of which use different protocols). That is where the major setup and operations costs are. The nature of the situation has resulted in the fastest connections (OC-128 or OC-256) being limited to only a smattering of locations. We would be far better off if the equipment to use these connections was much streamlined and lower cost. That would result in many more high speed connections and a much faster and much more robust internet.
Anybody remember Homer poking holes in the hood of his car with a pick? "Speed holes."
Cars/fibre optics - no big difference...
(Going out to put speed holes in his bike tires... D'oh!)
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Could these be produced by Si areogels as well?