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Bent Fibers Put Networks At Risk
opticsorg writes "The combination of moderate optical powers and tight bends can prove catastrophic for optical fibers, according to research carried out by BT Exact in the UK. Although the effect is unlikely to cause problems in current networks, it means that designers may need to think carefully before scaling up the power in their systems or deploying Raman amplifiers with pump powers of several hundred milliwatts or more. In the July 10th issue of Electronics Letters, Ed Sikora and his colleagues report that powers as low as 500 mW can induce permanent damage in singlemode fiber that is bent (13 mm bend diameter or less). 'These bends could be found in exchange racks or splice trays, for example, especially if a fiber is tugged or pulled,' Sikora told Optics.org. The BT researchers carried out tests on four types of fiber subjected to a range of bend diameters (5 to 15 mm) and optical powers of up to a few watts. In all cases the fibers fail within 53 hours. 'What was unexpected was that the catastrophic failure can occur in 90 bends at fairly low powers of less than 1 W or so,' said Sikora. 'It's important to understand that we're not saying that networks are going to fall over tomorrow, but as powers go up you have to aware this effect could occur under certain circumstances.'"
Similarly, the bends can prove catastrophic for nautical divers.
You should see the physics my network defies!
Don't bend your fiber. I could of swore not bending optial equipment was a given.....
...if you abuse copper conductors, they'll fail too.
I'm having a hard time saying this is surprising; minimum bend radius for fiber is nothing that hasn't been obvious to anyone working with the stuff. As long as you're treating it well, you'll be fine. If you or your upstream is stupid about how to handle it, well, it's like any other poor infrastructure, it's gonna bite you. No surprises there.
Im' no expert in this technology, but is it possible that somebody could remotely set up the power of the transmitter in such a way to produce this kind of damage on purpose.???
I always thought this was a given?
Whats new here that everyone whos so much as read a magazine article about fibre optic tech doesnt know?
You cant bend fibres, or light will just come shooting out.
I don't need no instructions to know how to rock!!!!
The zero's can turn corners easily enough, but those ones get hung up in the corners.
You would not believe how many mice cords this effects yearly.
Life moves pretty fast; if you don't stop and look around once in a while, you could miss it. -FB
Being a network engineer I deal with fibers in a 19" rack. You simply have to bend the fibers in order to keep a clean tidy rack which does not look like a spaghetti. But as long as it's just a simple patchcable which is broken and not a fiber burried somewhere deep, It's just a simple case of shit happens. Just make sure you have your cabletester nearby :)
I'm not a complete idiot... Some parts are missing.
Light still can't travel around corners.
/syle
Those little packets are deceptive. If you've ever been tempted to steal a packet from another set of noodles to double up on the flavor, I can tell you don't do it! Way too strong and salty to enjoy. Stick to one packet only and never try snorting the contents. Big mistake.
I don't know how the average fibre installer works today, but I know the few times I played with it, we always installed with corners were gentle enough that a full loop would be about 30 cm. This included ensuring no significant load on the fibre at the attachment points, so no 90 degree bends at the switch or server.
I'm only talking about the last few feet, not the 'last mile' of course, but if I upped the power and had a fibre failure, I'd be saying very rude things to the rep of the company that did the installation (if they survived the .bomb, of course).
Does it take to discover bending cables are bad?
Scientists today showed that electrical conducting wires can fail when run through a bathtub and that your car won't run after going over a cliff.
The researchers were said to be "disappointed".
42 - So long and thanks for all the fish.
They should put some Pantene Pro-V on them fibers.
/me pulls fire alarm.
It works for me!
No, wait . . . ok, well, at least that stuff isn't flammable.
No, wait . . . shit.
No kidding? Tight bends in fiber are a problem? You mean all those equations for theta max that we learned the first day in FO engineering class are correct? You gotta be kidding me! What a revolution! Next you'll be telling me that the sky is blue!
"Let's do this again, only using a method we like to call, 'the right way'"
In related news, cutting the CatV cable at random points through your building can be destructive to your network.
DeviantArt Page
NSFWAccording to the article the cause of failure is an increase in temperature in the fibers when bent.
"the damage is caused by an increase in temperature that occurs when the power leaks out of the fiber at a bend and is absorbed by its coating. This either causes the fiber coating to burn off leaving the silica beneath exposed or if the temperature is high enough (around 1100C) the fiber itself deforms giving rise to a large permanent optical loss."
It would seem that research needs to be done in the optical fiber coatings and their heat transfer properties as the fibers can handle the increased temperature, but the coatings can't. Either that or we are seeing the limits of fiber systems and the amount of load they can carry. Anyone know what the current coatings are made of, or any alternatives to these coatings that would alleviate these problems?
Perhaps this is a good stock tip... When you hear of a company that has created a new fiber optic coating that increases the amount of heat trasnferred away from fibers, jump on their stock.
MMORPG fan-boy? Prove your worth
I don't understand how anyone working with fiber would consider this new news.
MMORPG Master? Prove Your Worth
Folks, a 5mm bend is darned tight. 5mm is almost 1/5th of an inch. Even a 15mm bend is pretty tight - just over half an inch.
I'd take this "study" with a large block of saly, personally. I never bent myheliax abtebba cable this tight, and I doubt that any sane technician would try to bend glass optical cable this tight, either.
Lemon curry?
Dont bend the fiber wires??
I'd think that along with any type of high speed data carrying wire, you really dont want to bend that stuff.
Into MMORPG's? Check it out!
According to the BT researchers, the damage is caused by an increase in temperature that occurs when the power leaks out of the fiber at a bend and is absorbed by its coating. This either causes the fiber coating to burn off leaving the silica beneath exposed or if the temperature is high enough (around 1100C) the fiber itself deforms giving rise to a large permanent optical loss. The failure occurs more rapidly as the power level rises and the fiber diameter shrinks.
"A fairly small percentage of the power is absorbed but as it is absorbed it changes the structure of the coating causing some more absorption until there is a run away effect," said Sikora. "Depending on the input power the temperature can easily go up to 1000C or more."
Yes folks, that's all there was in the story that didn't get posted on the front page of slashdot. 2 more paragraphs and we wouldn't have even needed the link...
I recently performed some similar testing of my own. I was horrified to find that if my fibre had a bend radius of less than 5cm and I upped my laser power output to 2.34 gigawatts, the fibre cable would suffer catastophic failure. This failure usually also resulted in a small hole through my wall, my neighbour's wall, his neighbour's wall and so on.
We must be dilligent in our routing of fibre!
And don't pull hard on fibre cables, that tends to pull the heads away from the rubber coating, making the cables even more exposed to damage. Or to cause a kink that violates the bending contraints.
While this isn't a life or death situation, even in a production environment ( which should have redundant paths and whatnot built in ), it's probably a big pain in the ass for long runs.
Having said that, how is this anything new?
PC moderators can suck my White pierced, tattooed dick. If you think pride == hate, s/dick/Aryan meat mallet/g.
It said in the article that this stuff happens because the light leaks out the sides of the fiber and messes up the coating...would reflective coating destroy the usefulness of fiber? It seems like it would solve this problem...unless of course it ended up just heating up the fiber and melting it...does anyone know if I'm a complete idiot for suggesting this?
At the car parts store is ugly tubing in a closed "C" profile called wire loom. It is somewhat inflexible. It works. But that gets too much important stuff accomplished without enough consultancy firms and PHB's employed. Sheesh. The next thing you know people will be selling bottled water and canned air! (Shaking head.)
This would make a nice Sci Fi catastrophic scenario. Actually if it doesnt work, it still can be used in a fictitious technological context.
Improper handeling and installation of fiber can effect performance and even the operation of the fiber? The hell you say?
That must be in the book right after "An end-user that constantly runs over their cat5 cable with an office chair might eventually experience connectivity issues." and "Why does my server spontainiously re-boot when it's plugged in a power strip with five HP5000 laser printers?"
This brought to you by the Ministry for the Preservation of Stating the Obvious.
Using teleportation technology a malicious individual could remotely install a new high-output DWDM device on the fibre and turn it on. The resulting high-power outpu would surely cause such failures and the authorities would be powerless to trace down who did the teleportation.
"I bent my Wookie."
...when I'll hopefully be building my own house in a few years. Better allow enough space for optical cabling, adding it afterwards would be a pain if bend radius has to be that big.
When I was a student worker I was "volunteered" to pull cable. We were running fiber from the Science Center to the Health Professions building. At the time I had no idea what fiber was even made of, I just knew to take it from point A to point B. It was a pretty fun day though, I still remember swinging on the fiber like it was vine. Good times.
"The Internet is a fad." - WB
A clever person solves a problem. A wise person avoids it. -- Einstein
... the "new" thing being reported is the microbends fail by going opaque when higher optical powers are being transmitted in the fibers. For modern systems in most inter-city networks, the number of channels (40, 80, ...) is going up, as is the power per channel. This is a combination not seen earlier in installations where most fibers (bent or not) carried fairly low power signals.
Interestingly enough, microscopic dust particles are equally hazardous to the system's health at these high power levels. Dust particles caught in unclean connectors has been known to scatter enough power to fuse/weld (its those friggin laser beams) together the connector parts together.
yawn.
yes, 42.
Dang. I guess now I can't kink the fiber up and hold it till the IT guy looks down the end and gets packets sprayed all over his face as I drop it and run...
Optical fibres can be used as couplers between two lasers (the second laser amplifies the signal from the first). We use such a system in our lab, where average powers of 40-100W can be sent down a single fibre (multimode in our case). If the surface of the end of the fibre gets scratched, or if dust lands on it, the tip can explode. With each pulse (it's a 25kHz pulsed laser) another piece of fibre is destoyed, and it acts like a fuse. If you don't turn the laser off quickly you can soon lose kilometres of fibre. All that's left is a ringing in your ears and a few bits of scorched plastic.
'It's important to understand that we're not saying that networks are going to fall over tomorrow, but as powers go up you have to aware this effect could occur under certain circumstances.'
I'm not saying a meteor is going to hit Earth tomorrow, but I just want you to be aware that it MIGHT happen in the future under certian circumstances.
-Valiss
Does anyone know of supplemental cladding (preferably something more sophisticated than a thick layer of duct tape) that can be added to the cable at critical points to prevent excessive bending while still allowing a reasonable degree of flexibility?
Please donate your spare CPU cycles to help fight cancer and other diseases
Heh. Setec Astronomy..
"I can't give you a brain, so I'll give you a diploma" - The Great Oz (blatently stolen sig)
This is a good reason to keep your optical fiber cables hidden when it is outside the server room.
I've been to more then one place where a major fiber is laying there in the open. I could easily see a disgruntled worker bending the cable a little bit. The fiber in these installations is usually for some mission-critical app, a bend fiber can cause a big financial loss.
With cut copper cable, it's easy to spot the two broken strands of cable. With fiber, it's harder to spot. Someone could easily bend the cable, and then straighten it out. All that's left is a minor kink in the wire and the plastic sheathing that is discolored from being stretched.
"Can of worms? The can is open... the worms are everywhere."
No crap, 5mm or 15mm, you're basically creasing the fiber. Imagine a 90 degree bend, with light coming in. Duh, it's going to hit that corner a lot. Duh it'll heat up. Duh, insulation goes bad from heat.
Slashdot should have an "obvious" topic or tag... or are they catering to the complete idoits who have been showing up more and more?
"Bent Fiber Put Networks at Risk"
No shit?
In other new, magnet endanger floppy disk and metal shrapnel is bad for your eyes
Maybe we should all be considerate and send data with less 1's and more 0's. When sending emails, don't use uppercase letters, try to use websites that use no graphics, and for gods sake, don't compress or encrypt anything!
_______
2B1ASK1
I design and build fiber-coupled semiconductor lasers as a day job, and some of the stuff in our R&D lab has a significantly higher power than what is currently used in most systems out there. A fiber bend radius that leaks/absobs x% of the power at 10mW with no difficulty becomes dangerous when you put a 5W laser in the system - the amount of leaked power becomes enough to fry fiber claddings (especially if the fiber was metalized for soldering to a package) and make a crunchy black line where a perfectly good bit of cable had been moments before.
The take-home message of all of this is that as optical powers go up to increase bandwidth, some existing fiber installation methods may need to be re-thought. That said, I'd doubt that this will have much of an impact on many systems outside of long-haul lines since local systems don't need to have powers of this type to get the bits across town or around an office building.
Is it still has tedious to put the connectors on the ends?
When I was doing it, IIRC, the process ran something like this:
Is this related to "Bent Bishop puts Episcopalian Church at Risk?"
Are networks prejudiced to "straight" fibers? Will there be protests?
Reading Slashdot is ruining my spelling and grammar.
Judging by some of the content of the Internet, I'd say all the fibers are seriously bent.
--- Ban humanity.
In grad student (chemistry) days I ran an apparatus for stimulated, mass-selective Raman spectroscopy of molecular clusters. The Raman pump beam was two colors, generally tuned for power (a watt or two each, depending on tuning). The molecular clusters were formed in a vacuum chamber and we had a quartz window to let the laser light in. If there was a speck of dust on the window at the point the beam entered, the absorption was sufficient to start drilling a hole in the window. The noise was our cue to cut the laser beam before the window was breached (there were dedicated electronic circuits to protect the vacuum chamber's diffusion pumps, but we didn't want to take the risk of failure).
Of course, we spent a lot of time cleaning that window, and for that matter all the optics.
The clearance system sounds logical. It is not. It is completely arbitrary. -- John Bolton
It's perfectly possible for multimode fiber to be glass and single-mode to be plastic. The difference is the diameter of the waveguide itself. Single-mode fibers (At least the waveguide portion, the total fiber is usually similar in thickness for structural reasons) are much thinner than multi-mode fibers, only allowing one waveguide "mode" to exist. (Hence single-mode). Each mode in a waveguide travels at slightly different velocities (Actually, in reality the light travels in the same speed, but certain modes travel longer distances due to the way they bounce within the waveguide), so multimode fiber suffers from pulse spreading since not all of the light travels the same distance.
Glass vs. plastic - Glass is always more transparent. As a result, singlemode fibers ARE usually made from glass since there's not much point in reducing pulse spreading if your attenuation is not reduced.
retrorocket.o not found, launch anyway?
DOn't use fiber to tie up your girlfriend to the bed posts while downloading pr0n.
It's so fun that my network crashed and bursts into flames! Somebody put that server out! ;)
This space is not for rent.
Wouldn't that be AITHER from Greek Mythology?
Optical Powers.. Light God... God of Light...
I crack myself up!
Get Bent.
I'm suprised I'm the first to post this.
Aside from the obvious, DUH!, the biggest problem I've found is right at the equipment where the plug is. Most equipment have the plug hole perpendicular to the front face (insert sexual pun here). Consequently, the LEDs and labels and everything else is on the face as well, so most engineers/technicians try to keep it clean. Keeping it clean is why the bending happens. I've only seen a few equipment vendors make plug holes that were at an offset angle more lateral to the face. Smart design. More equipment vendors need to follow.
Cisco are you listening? Ya dumb clod.
"Last one in is a rotten goblin!" - Kepp
Simply save all your viagra spam and transmit it down the bent cable, that'll straighten it out!
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
This should be modded funny, not off-topic.
Are you affraid of what might put your network at risk? Then let me help you be affraid:
If you know nothing about networks your network could be at risk of:
bent fiber
bent copper
bent pins
unseated memory
old equipment
unlocked network closets
lazy admins
stupid users
uneducated management
sun spots
anything
everything
Get the point?
And I'm not kidding. Using dBm = 10 log10[ P / 1 mW], you get 27 dBm.
Most lasers in the telecommunications world run between -10 dBm and 5 dBm. Over a good fiber link, you can reach over 100km with a couple dBm.
EDFAs and Raman amplifiers may be up in the 20 or 30 dBm range, but they are not widely used, nor will they ever be. You only need that much power for very long runs - like between remote cities in the mid-West US.
-- PGP keyID: 0x4C95994D
When people do fiber audits on carrier networks on large cables, they macrobend fiber and watch an OTDR to see where it's bent. This is nothing new, but I will say that I've seen fiber bent worse than this that has been carrying carrier-grade equipment light for years.
"Depending on the input power the temperature can easily go up to 1000C or more."
Network failure is bad, but isn't the fire risk an even greater danger?
How small a thought it takes to fill a whole life
Raise your hand if you didn't know bending fiber optic at sharp angles was bad
Just a solar eclipse...
It's better to be the foot on the boot than the face on the pavement. ~~ tkx Kadin2048
I was recently called in to investigate network trouble at an office. The network laser printer frequently went offline and lost jobs, and no one could figure out why. I traced the cable and found that it went through a door hinge before plugging into the ether switch. The door couldn't close completely due to the cat-5 cable, and there was about 6" of "bite marks" along the cable where it had been pinched between the door and the frame. Changing the cable and rerouting away from any doors (the office had a drop ceiling, so that was easy) fixed the problems.
I was most surprised by this because the office was in support of an adjacent colocation facility which had beautifully structured fiber and copper running from rack to rack. But I've seen frat houses with better wiring than the office!
Today, normal enterprise/campus networks don't work with any amount of power, quite honestly. Horizontal building cable is almost exclusively copper or multi-mode fiber, and riser/inter-building cable is single-mode, but relatively cheap stuff. Where this kind of thing comes into play is in the long-haul networks of companies like AT&T, Level 3, Sprint, etc., where you have 100Km+ between OA (Optical Amplifier) sites.
:-)
Many people are working to extend the OA interval to 600Km through doped and Raman amplifiers, which are giving you launch powers in the 30db+ range, and are starting to approach the powers that can do this. However, as someone pointed out, none of this happens with normal correct fiber installation. I know my company, which runs a large (tens of thousands of miles) network has reams of paper describing exact splice tray designs, stress on cables, bend angles. It goes down to how you support things going in and out of a OA, etc., and addresses the radius, which I believe we try and keep around 15-20cm minimum.
If you follow smart rules, these don't matter. If you don't, well, it probably won't affect anyone who is working outside the large telco space. The cost of an EDFA (Erbium doped fiber amplifier) is tens of thousands of dollars.
No story, move along.
Having worked at JDS Uniphase (world's biggest fiber component manufacturer) for several years, the minimum bend radius is not a suggestion, it is a requirement, especially when you crank the laser power. READ THE LABELS AND FOLLOW THEM!!!
:)
But, when you try make something idiot-proof, the world will make a better idiot.
Long-term, I think the only solution is change the plastic cladding, so that it can't be bent beyond the minimum radius of the fiber.
(and no, I don't work at JDS anymore. But it was fun and I made a pile on the stock
Obviously I meant the minimum radius of curvature, not the maximum.
When we did our first (thickwire) Ethernet installation, we were impressed with all the warnings about the importance of maintaining, IIRC, a six inch bend radius. Just for fun, we took a scrap piece with the idea of bending it too sharply just to see what would happen. What we found was that the cable was very, very hard to bend. It seemed that you'd need tools--or a very muscular person trying very deliberately to bend it--to violate the spec.
So, what's the situation with optical fiber? A 13 mm bend diameter sounds likea pretty sharp bend to me. Is it something that you could easily do unintentionally? Or only something that happens when you know you're in a tight spot and are deliberately forcing it?
"How to Do Nothing," kids activities, back in print!
You've never played Twister, have you?
Compression and tension are not the issues. The failure is not a result of material properties. Optical fibers leak energy at bends becasue the electromagnetic field is not completely contained within a fiber.
The parent of this comment is greatly overrated.
bite my shiny metal ass!
my sig
The article states that 4 different types of fiber were tested, but doesn't state what those types are, or related too. There are different materials fiber optic cabling can be made out of, as well as different diameters. Were they talking about different diameters, or the materials?
This was obviously written for a somewhat technical audience, given the subject matter and source that published it. By omitting the facts of which 4 types they tested, it really doesn't do justice to the subject. For all we know, they tested low end cabling made from plastics.
A slip of the foot you may soon recover, but a slip of the tongue you may never get over. -Benjamin Franklin
We repulled all our fiber when we moved our data center. The old fiber was lame plastic jacketed single strands.
The new stuff has 8 strands and is inside what I can only describe as being like Liquidtight Metallic Conduit -- a heavy plastic jacket over a coiled metal jacket. Where it's pulled and "publicly" accessable (common closets), it'd be impossible to bend it without a hacksaw.
AAAAAA! Blast it! I'm all out of mod points!
Standing at the very edge of my imagination, I peered into the inky void and realised -- I couldn't think up a new sig.
I spent many years working in fiber optics. Bending-induced failure modes have been well known for decades.
Is 802.11(a,b,g) not fast enough for you? Wherever you put the wire/fiber/whatever, it'll be in the wrong place and obsolete in 5 years. If your feed isn't faster than, say, 11Mb/second, why bother with anything other than wireless?
Manufacturers should build them stiffer or add a structure that doesnt allow the fibers to be bent that much. It will be really hard for network admins to lay their cables *very carefully* only to trip on it and break it.
"Give orange me give eat orange me eat orange give me eat orange give me you." -Nim Chimpsky
"A fairly small percentage of the power is absorbed but as it is absorbed it changes the structure of the coating causing some more absorption until there is a run away effect," said Sikora. "Depending on the input power the temperature can easily go up to 1000C or more." I read this too, not sure how much power is required but it seems like a good heating element.
Damn, slow down Timmy. Quality not quantity. How is this even interesting? Who cares, there are plenty of potential problems when you design networks. Are we going to have a story about each of them?
3) Don't click on TubaGirl or Goatse.cx links.
Everybody who uses single mode fibers know not to bend them, because bending induces mode mixing. Bend the fiber and it's not single mode anymore.
Chromatic dispersion (Different wavelengths traveling at different speeds) and modal dispersion (Different modes traveling at different speeds.) are two different mechanisms.
While eliminating modal dispersion won't eliminate chromatic dispersion, IIRC, modal dispersion is a MUCH larger effect than chromatic dispersion. (From what I recall from three years ago, it was an order of magnitude more - I'd have to dig up my old notebooks from my optics class.)
Also, there's no way to reverse modal dispersion, while chromatic dispersion can be reversed by using fiber of two different materials - One that causes longer wavelengths to travel faster, and a second one that causes longer wavelengths to travel slower, reversing the effects of dispersion in the first section of fiber.
retrorocket.o not found, launch anyway?