Path: utzoo!attcan!uunet!mailrus!ames!sgi!rpw3@rigden.wpd.sgi.com From: rpw3@rigden.wpd.sgi.com (Rob Warnock) Newsgroups: sci.electronics Subject: Re: tapping into a fiber optic cable Message-ID: <61464@sgi.sgi.com> Date: 2 Jun 90 05:25:43 GMT References: <61338@sgi.sgi.com> <3332@ash31.UUCP> Sender: rpw3@rigden.wpd.sgi.com Reply-To: rpw3@sgi.com (Rob Warnock) Organization: Silicon Graphics, Inc., Mountain View, CA Lines: 39 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