Xref: utzoo comp.arch:17394 sci.electronics:13153 sci.physics:13799 comp.lsi:1105 Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uwm.edu!bionet!ames!uhccux!virtue!comp.vuw.ac.nz!munnari.oz.au!bruce!trlluna!rhea.trl.oz.au!aduncan From: aduncan@rhea.trl.oz.au (Allan Duncan) Newsgroups: comp.arch,sci.electronics,sci.physics,comp.lsi Subject: Re: Electro-optic bus Message-ID: <1965@trlluna.trl.oz> Date: 27 Jul 90 06:32:12 GMT References: Sender: root@trlluna.trl.oz Distribution: comp Lines: 30 From article , by aglew@oberon.crhc.uiuc.edu (Andy Glew): ... > We know that optics can achive high bandwidth, ie. throughput. > > But what is the latency of an electro-optic system? > Eg. what would be the time to covert from a > - GaAs electronic (voltage) signal, > - to optics (typically via a laser diode, hopefully on the GaAs chip) ^^^^^ > and then to receive ... A laser might not be the best - they have a delay from zero curent while a population inversion is created. Normally they are used with _varying_ intensity rather than off/on, so there is added complexity, as well as the (current) need to edge couple to the fibre. LEDs are better unless you want coherence. What you end up with is a pipeline, rather than a bus, maybe this will better match the current crop of pipelined CPUs :-) Overall, there is little, if any, advantage in electro-optic busses. If it was all optic, then that might be different, but even then you are only talking pipes, as the trip time to an adjacent slot is significant. Allan Duncan ACSnet a.duncan@trl.oz (03) 541 6708 ARPA a.duncan%trl.oz.au@uunet.uu.net UUCP {uunet,hplabs,ukc}!munnari!trl.oz.au!a.duncan Telecom Research Labs, PO Box 249, Clayton, Victoria, 3168, Australia.