Xref: utzoo comp.arch:17485 sci.electronics:13300 sci.physics:13872 comp.lsi:1120 Path: utzoo!attcan!uunet!zephyr.ens.tek.com!tekcrl!tekgvs!arnief From: arnief@tekgvs.LABS.TEK.COM (Arnie Frisch) Newsgroups: comp.arch,sci.electronics,sci.physics,comp.lsi Subject: Re: Electro-optic bus Message-ID: <7914@tekgvs.LABS.TEK.COM> Date: 2 Aug 90 15:00:44 GMT References: <1965@trlluna.trl.oz> Reply-To: arnief@tekgvs.LABS.TEK.COM (Arnie Frisch) Followup-To: comp.arch Distribution: comp Organization: Tektronix, Inc., Beaverton, OR. Lines: 25 In article aglew@oberon.crhc.uiuc.edu (Andy Glew) writes: >>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. Wrong! LEDs exhibit generally poor bandwidth or rise-time of the optical output. In addition, because of their broad linewidth, they are highly subject to dispersion when transmitting fast pulses over moderate distances. > > >So, what is the ballpark delay? Laser and/or LED? >Tens or hundreds of ns? > > Laser delay is a function of several factors, type of laser, modulator rise time, even output load, but 100 to 200psec is probably typical. I haven't measured any LEDS because I never considered them suitable for the reason cited above. Arnie Frisch Tektronix Laboratories