beckman@iuvax.cs.indiana.edu (Peter Beckman) (05/31/90)
Can a fiber optic cable be "tapped" into without disturbing the data being transmitted? I would like to run some fiber optic cable through some expensive equipment to prevent theft. Loss of the signal would mean the cable has been cut, and an alarm would sound. A simple copper wire threaded through equipment could be easily spliced around. Could a fiber optic cable be similarly bypassed? How easily? -Pete beckman@iuvax.cs.indiana.edu
dt@yenta.alb.nm.us (David B. Thomas) (05/31/90)
beckman@iuvax.cs.indiana.edu (Peter Beckman) writes: >Can a fiber optic cable be "tapped" into without disturbing the data Yes, and a guy I know had his patent stolen on that one. I don't have the patent number, but it exists, so try your local patent repository. What?? you don't have a local patent repository? Well, I knew there was something I liked about albuquerque! David dt@yenta.alb.nm.us
henry@utzoo.uucp (Henry Spencer) (05/31/90)
In article <46249@iuvax.cs.indiana.edu> beckman@iuvax.cs.indiana.edu (Peter Beckman) writes: >Can a fiber optic cable be "tapped" into without disturbing the data >being transmitted? I would like to run some fiber optic cable through >some expensive equipment to prevent theft. Loss of the signal would >mean the cable has been cut... Bypassing fiber would be possible in theory, I think, but if people with that sort of resources want your equipment, better just give it to them. :-) Not impossible but not easy.
dannie@coplex.UUCP (Dannie Gregoire) (05/31/90)
beckman@iuvax.cs.indiana.edu (Peter Beckman) writes: >Can a fiber optic cable be "tapped" into without disturbing the data >being transmitted? I would like to run some fiber optic cable through If I recall correctly, it can be tapped without distubing transmitted data. I remeber reading an article in Info World about a year ago about just such a method. It seems that if you bend a FO cable at more than 90 degrees that about 20% of the signal will "bleed" out of the cable at the bend. An opto-receiver can be installed there with an amplifier to read the signal without disturbing any data. \\-------------------\\ \\ Dannie Gregoire \\ \\ (dannie@coplex) \\ \\-------------------\\
grege@gold.GVG.TEK.COM (Gregory Ebert) (05/31/90)
In article <46249@iuvax.cs.indiana.edu> beckman@iuvax.cs.indiana.edu (Peter Beckman) writes: >Can a fiber optic cable be "tapped" into without disturbing the data >being transmitted? Yes, and no. Any 'tapping' will reduce the amount of energy sent to the receiver, unless you install a 'repeater'. The loss in energy may or may not be an important issue. Regarding security, there will be a period of time which the cable is 'broken', thus a break-in will be detected. Even if you tap-in without initial detection, there is equipment available (OTDR- Optical Time Domain Reflectometry) which will detect even _minute_ variances in line impedance, and their exact location. This technique is commonly used in the electrical realm to find flaws in coax cable; it's so sensitive that you can squeeze or bend the cable and get a detectable reflection. Ask any cable TV technician about how they detect and bust bootleggers. All this aside, I've heard that someone manufactures fiberoptic cable which can be pressurized with some gas; cut/poke/tap/etc the cable, and the pressure drop signals an alarm. Bizarre.
gene@cooper.cooper.EDU (Gene (the Spook) ) (06/01/90)
in article <46249@iuvax.cs.indiana.edu>, beckman@iuvax.cs.indiana.edu (Peter Beckman) says: > Can a fiber optic cable be "tapped" into without disturbing the data > being transmitted? I would like to run some fiber optic cable through > some expensive equipment to prevent theft. Loss of the signal would > mean the cable has been cut, and an alarm would sound. A simple > copper wire threaded through equipment could be easily spliced around. > Could a fiber optic cable be similarly bypassed? How easily? -Pete I remember a blurb in a recent issue of ECN about a "fiber tap", which bends the fiber just enough to let a small amount of light leak through and be picked up with (probably) a phototransistor. Sorry I can't be of more help, but I trashed the magazine as soon as I finished reading it. Spookfully yours, Gene
rpw3@rigden.wpd.sgi.com (Rob Warnock) (06/01/90)
In article <151@coplex.UUCP> dannie@coplex.UUCP (Dannie Gregoire) writes: +--------------- | >Can a fiber optic cable be "tapped" into without disturbing the data... | I remeber reading an article in Info World about a year ago about just such | a method. It seems that if you bend a FO cable at more than 90 degrees | that about 20% of the signal will "bleed" out of the cable at the bend. | An opto-receiver can be installed there with an amplifier to read the signal | without disturbing any data. +--------------- In fact, there are companies [not mine] out there working on using this phenomenon to build practical fiber-optic "quick-connects". The idea is that instead of the current labor-intensive cut, epoxy, cure, polish, examine, polish, examine... sequence to terminate fibers to "ST" connectors, one would simply strip off the outer jacket, stick the bare fiber into a hole, and twist down on a knob which would bend the fiber up against the receiver or LED (yes, you can *send* this way, too). Look for such commercial products in a year or so. Look for it to eventually make fiber installation a *lot* cheaper than RS-232. -Rob ----- Rob Warnock, MS-9U/510 rpw3@sgi.com rpw3@pei.com Silicon Graphics, Inc. (415)335-1673 Protocol Engines, Inc. 2011 N. Shoreline Blvd. Mountain View, CA 94039-7311
tell@rudolph.cs.unc.edu (Stephen Tell) (06/01/90)
In article <151@coplex.UUCP> dannie@coplex.UUCP (Dannie Gregoire) writes: >beckman@iuvax.cs.indiana.edu (Peter Beckman) writes: >>Can a fiber optic cable be "tapped" into without disturbing the data >>being transmitted? I would like to run some fiber optic cable through >If I recall correctly, it can be tapped without distubing transmitted data. >I remeber reading an article in Info World about a year ago about just such >a method. It seems that if you bend a FO cable at more than 90 degrees >that about 20% of the signal will "bleed" out of the cable at the bend. >An opto-receiver can be installed there with an amplifier to read the signal >without disturbing any data. >\\ Dannie Gregoire \\\\ (dannie@coplex) \\ some minor items of information: "tapping" this way is detectable in two ways: The ammount of light recieved at the other end will be reduced; although most recievers will be designed & selected to have some tolerance of reduced levels before failing to recieve reliably. This is to account for the reduction in output level of LEDs and laser diodes as they age. It can also be detected with a time-domain reflectometer, as noted by someone else in this forum. I believe that this tapping technique is sometimes used to verify the quality of a splice or connector without having to go down to the other end of the cable. Even if that was convenient, you might not be able to tell which end you had to re-terminate. I'm not sure how common this practice is, or if the equipment used could be adapted for tapping of active lines, but it is concievable that the necessary equipment to tap a data fiber could be more common than you would like. -------------------------------------------------------------------- Steve Tell tell@wsmail.cs.unc.edu CS Grad Student, UNC Chapel Hill.
davet@tsdiag.ccur.com (Dave Tiller N2KAU) (06/01/90)
In article <151@coplex.UUCP> dannie@coplex.UUCP (Dannie Gregoire) writes: -beckman@iuvax.cs.indiana.edu (Peter Beckman) writes: - ->Can a fiber optic cable be "tapped" into without disturbing the data ->being transmitted? I would like to run some fiber optic cable through - -If I recall correctly, it can be tapped without distubing transmitted data. - -I remeber reading an article in Info World about a year ago about just such -a method. It seems that if you bend a FO cable at more than 90 degrees -that about 20% of the signal will "bleed" out of the cable at the bend. But since this is to be used for a security system, wouldn't this 20% loss of signal be noticed? I think this is an excellent idea! I just happen to have some low-grade plastic fiber laying around - I think I'll use it! -- David E. Tiller davet@tsdiag.ccur.com | Concurrent Computer Corp. FAX: 201-870-5952 Ph: (201) 870-4119 (w) | 2 Crescent Place, M/S 117 UUCP: ucbvax!rutgers!petsd!tsdiag!davet | Oceanport NJ, 07757 ICBM: 40 16' 52" N 73 59' 00" W | N2KAU @ NN2Z
svoboda@motcid.UUCP (David Svoboda) (06/01/90)
From article <61338@sgi.sgi.com>, by rpw3@rigden.wpd.sgi.com (Rob Warnock): > In fact, there are companies [not mine] out there working on using this > phenomenon to build practical fiber-optic "quick-connects". The idea is > that instead of the current labor-intensive cut, epoxy, cure, polish, > examine, polish, examine... sequence to terminate fibers to "ST" connectors, > one would simply strip off the outer jacket, stick the bare fiber into a hole, > and twist down on a knob which would bend the fiber up against the receiver > or LED (yes, you can *send* this way, too). > > Look for such commercial products in a year or so. Look in your handy-dandy Inmac catalog. A year and a half ago I installed a fiber optic "parallel cable" on an unruly laser printer. The setup consisted of an optic xcvr at either end (a black box the size of a null modem) and a two "conductor" plastic optic cable. Just strip, stuff, and twist, as you said. About 130 bucks for two xcvrs and a cable. Extends a parallel connection a LONG way, with no EM noise whatsoever (of course). Dave Svoboda, Motorola CID, RTSG, Arlington Heights, IL uucp => {uunet|mcdchg|gatech|att}!motcid!svoboda internet => motcid!svoboda@chg.mcd.mot.com I don't waste my money; I invest it in ventures with high negative returns.
rpw3@rigden.wpd.sgi.com (Rob Warnock) (06/02/90)
In article <3332@ash31.UUCP> svoboda@motcid.UUCP (David Svoboda) writes: +--------------- | From article <61338@sgi.sgi.com>, by rpw3@rigden.wpd.sgi.com (Rob Warnock): | > In fact, there are companies [not mine] out there working on using this | > phenomenon to build practical fiber-optic "quick-connects"... | Look in your handy-dandy Inmac catalog. A year and a half ago I installed a | fiber optic "parallel cable" on an unruly laser printer. The setup consisted | of an optic xcvr at either end (a black box the size of a null modem) and a | two "conductor" plastic optic cable. Just strip, stuff, and twist, as you | said. About 130 bucks for two xcvrs and a cable... +--------------- You are talking about *plastic* fiber, at *low* speeds. That plastic stuff, usually 1mm diameter, has enormous loss, typically .3-.5 dB/meter, and bad dispersion, usually .5-1 ns/meter. That means at 10 Mb/s data rates ypu can go at most 30-50 meters. (Yes, I have pushed Ethernet packets down el cheapo Hewlitt-Packard plastic fiber.) This plastic stuff is nice, but it's the "RS232" of fiber. And it's not "bent-fiber", but "easy termination" (with an eXacto knife) of a more-or-less standard (but plastic and thus low-cost) butt-connect (straight end-on). It's the large 1000 micron aperture, over 50 times the area of even the largest glass fibers, that lets this work in the presence of sloppy alignement. And the 2-4 dB of the resulting crude termination gets lost in the high loss of the fiber itself. So it's a win, at very low speeds and very short distances. But I was talking about being able to quick-connect, say, low-loss 62.5 micron glass, the 500 MHz-km stuff you use for FDDI that carries the 100 Mb/s data rate (125 Mbaud) for up to 2 km per hop. "Bent-fiber" connectors for such glass don't exist on the open market yet. But when they do, they'll start to give "10baseT" twisted-pair Ethernet some real competition... -Rob ----- Rob Warnock, MS-9U/510 rpw3@sgi.com rpw3@pei.com Silicon Graphics, Inc. (415)335-1673 Protocol Engines, Inc. 2011 N. Shoreline Blvd. Mountain View, CA 94039-7311
fmgst@unix.cis.pitt.edu (Filip M Gieszczykiewicz) (06/04/90)
Greetings. About 20% loss if bent... What you people don't realize is that one can very easily protect against someone bending the cable.. Simply have 2 pots (or a more complex circuit) and preset the INTENSITY of "1" and the intensity of "0"... That is, don't make "1" be FULL ON and "0" FULL OFF. What you want is a loop with a serial word "looping" in the cable. If someone bends the cable, either the "1" or the "0" will not have the same level... partity error is detected and "all hell breakes loose" :-) If the serial reciever/transmitter is fast enough, you don't even need a partity checker, just a plain comparator will do just fine. Take care. P.S. Whay the whole mess of the serial I/O controller?? Well, what is the potential "fiber bender" (like "fender bender" ;-) prepared for? a simple on/off pulser and/or pressure jacket or for a complex sequence of high speed bits running along? I rest my case :-) -- _______________________________________________________________________________ "The Force will be with you, always." It _is_ with me and has been for 10 years Filip Gieszczykiewicz "..of future fame...." "Ok! So I have a dream..." FMGST@PITTVMS or fmgst@unix.cis.pitt.edu "My ideas. ALL MINE!!"