steves@tektools.UUCP (01/23/87)
A consortium of countries is laying a fiber optic cable under
the Atlantic from the US to France and England. Before beginning
this, they beta-tested a piece of the cable off the Canary Islands.
According to Time magazine, this test gave the following results:
[This is not an exact quote, but is what I remember]
"A certain kind of radiation, escaping from the cable, attracted
alligator sharks which chomped through the cable. The solution
was to use heavier armour."
My question: what kind of radiation escapes from a *fiber optic*
cable? After thinking about it for a while, I suppose that there
could be repeaters inside the cable that are powered by plain
old copper wires, and the current could generate an electro-magnetic
field. But wouldn't the armor act as a shield?
Anyone have any information? Just curious.
Steve Shellans
Tektronix, Beaverton OR
{decvax, wyvax, ihnp4, ucbvax} !tektronix!tektools!steveshenry@utzoo.UUCP (Henry Spencer) (01/25/87)
> "A certain kind of radiation, escaping from the cable, attracted > alligator sharks which chomped through the cable. The solution > was to use heavier armour." > > My question: what kind of radiation escapes from a *fiber optic* > cable? After thinking about it for a while, I suppose that there > could be repeaters inside the cable that are powered by plain > old copper wires, and the current could generate an electro-magnetic > field. But wouldn't the armor act as a shield? Yup, you got it, there are repeaters in there, powered by plain old high-voltage DC as I recall. The "armor" they are speaking of may not be metallic, and even so I'd wonder about incomplete shielding. A lot of the comsat people were kind of happy about this -- fiber looks like nasty competition for them. But one observer commented something like "if this is the best argument against fiber, I'd say 'boy, the satellite people are getting desperate'". -- Legalize Henry Spencer @ U of Toronto Zoology freedom! {allegra,ihnp4,decvax,pyramid}!utzoo!henry
witters@fluke.UUCP (01/27/87)
> According to Time magazine, this test gave the following results: > [This is not an exact quote, but is what I remember] > > "A certain kind of radiation, escaping from the cable, attracted > alligator sharks which chomped through the cable. The solution > was to use heavier armour." > > My question: what kind of radiation escapes from a *fiber optic* > cable? Here again, we see an example of the technical illiteracy of most journalists. I think it is much more likely that some kind of gas was escaping from the plastic used to make the cable, and the gas odor was what attracted the sharks. Sharks have a very good sense of smell. I bet the journalist who reported the story was told this, but mis-interpreted what (s)he was told, and reported that radiation was attracting sharks rather than the smell of the cable. Also, the spelling of 'armour' leads me to suspect that the original story may have come from some British tabloid :-) (just joking, folks). -- I'm not a lumberjack John Witters and I'm not O.K. John Fluke Mfg. Co. Inc. P.O.B. C9090 M/S 245F Everett, Washington 98206 (206) 356-5274
edhall@randvax.UUCP (01/31/87)
In article <1763@vax1.tc.fluke.COM> witters@tc.fluke.COM (John Witters) writes: >> According to Time magazine, this test gave the following results: >> [This is not an exact quote, but is what I remember] >> >> "A certain kind of radiation, escaping from the cable, attracted >> alligator sharks which chomped through the cable. The solution >> was to use heavier armour." >> >> My question: what kind of radiation escapes from a *fiber optic* >> cable? > >Here again, we see an example of the technical illiteracy of most journalists. >I think it is much more likely that some kind of gas was escaping from the >plastic used to make the cable, and the gas odor was what attracted the sharks. >Sharks have a very good sense of smell. ``Radiation'' might be a little inaccurate, but it is entirely possible that a DC electic field from the cable (which, as Henry Spencer pointed out, contains wires carrying DC for repeaters) is what attracted the sharks. According to Science News of several months back, certain sharks have been found to be extremely sensitive to small electric fields, and may well use them as aids in locating certain prey. This is just another in a set of unusual biological senses that have been discovered in recent years (like magnetic senses in birds, infrared vision in reptiles, or ultraviolet vision in insects). Of course, in this case a chemical cause makes just as much sense. A point to ponder--technical people are often just as illiterate outside of their own specialty as you accuse journalists of being. True polymaths are rare in this day and age. -Ed Hall decvax!randvax!edhall
chrise@ihlpl.UUCP (02/02/87)
> > > > My question: what kind of radiation escapes from a *fiber optic* > > cable? > > I think it is much more likely that some kind of gas was escaping from the WRONG! The EMR was/is not coming from the fiber, its coming from the power cables wrapped around the fiber core used to transmit power to the under-sea repeaters. AT&T was aware that a problem might exist due to previous instances with "copper" cable. What they did not anticipate was the frequency of occurence which has apparantly increased due to the increased power levels for the FO repeaters. Chris Edmonds @ AT&T Something-or-Other, Naperville, IL ...!ihnp4!ihlpl!chrise ********************************************************** "...Earth, named for its finely crushed rock containing organic matter capable of supporting such advanced lifeforms as Catholics and Lutherans." Garrison Keilor