Post by thread:[OT]: About smart dust and more

The whole MAV thing combined with this, though it seems to be for applications like weather stations, makes me paranoid. I fear for the well being of privacy. They noted that 1Mbps is plenty for transferring real-time video with modest compression that can be done in hardware. It looks to me like James Bond's newest surveillance toy. Aside from that, très cool. Check out fsona for something similar, though a different applicaion and higher data rates. http://www.fsona.com/ They're designing golden mile comm applications golden mile for those who don't know is the last mile distance between the fibre-optic backbone of a network and the businesses wanting connections. Typically, this is the most expensive portion of the entire connection (if you have to rip up a street to put in your fibre connection, you know that you'll be paying through the nose for it) Fsona's tech is based on laser comm similar but much more powerful than that depicted in the article listed by Peter (though as I said before, it is for a different purpose) and it provides quite reliable (can be interrupted by the occasional bird for a few ms) connections. I think it's a great idea. Cheap installation (in $/Gbps terms). Cheap maitainance compared to other techs of similar BW. Looks good to me. {Original Message removed}

Of course the golden mile is important, especially if you can DIY and if you can skip the backbone altogether ;-). Look for a DIY point to point 10MBps optical link from Czechia called metropolis. URL: http://atrey.karlin.mff.cuni.cz/~clock/twibright/ronja/ Peter PS: I'd like to hear of places where students/techies/geeks formed point-to-point networks like this, not unlike UUCP nets used to be. Know any ? On Mon, 8 Jul 2002, Brendan Moran wrote: {Quote hidden}>The whole MAV thing combined with this, though it seems to be for >applications like weather stations, makes me paranoid. I fear for the well >being of privacy. They noted that 1Mbps is plenty for transferring >real-time video with modest compression that can be done in hardware. > >It looks to me like James Bond's newest surveillance toy. > >Aside from that, très cool. Check out fsona for something similar, though a >different applicaion and higher data rates. > >http://www.fsona.com/ > >They're designing golden mile comm applications > >golden mile for those who don't know is the last mile distance between the >fibre-optic backbone of a network and the businesses wanting connections. >Typically, this is the most expensive portion of the entire connection (if >you have to rip up a street to put in your fibre connection, you know that >you'll be paying through the nose for it) > >Fsona's tech is based on laser comm similar but much more powerful than that >depicted in the article listed by Peter (though as I said before, it is for >a different purpose) and it provides quite reliable (can be interrupted by >the occasional bird for a few ms) connections. > >I think it's a great idea. Cheap installation (in $/Gbps terms). Cheap >maitainance compared to other techs of similar BW. Looks good to me. > >{Original Message removed}

> Of course the golden mile is important, especially if you can DIY and if > you can skip the backbone altogether ;-). Look for a DIY point to point > 10MBps optical link from Czechia called metropolis. URL: > err... I had thought that several GBps was in a little bit of a different class. Anyways, anyone know how high a datarate you can get out of the LED in a laser pointer? -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spam_OUTlistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

On Tue, 9 Jul 2002, Brendan Moran wrote: >> Of course the golden mile is important, especially if you can DIY and if >> you can skip the backbone altogether ;-). Look for a DIY point to point >> 10MBps optical link from Czechia called metropolis. URL: >> > >err... I had thought that several GBps was in a little bit of a different >class. Anyways, anyone know how high a datarate you can get out of the LED >in a laser pointer? In theory, about c/(2*lambda) Hz (== Bauds in this case). In practice, as much as you can drive the device to. Diodes for high data rates have special design (like controlled impedance feeds and such). I once had a book that showed how to interface a laser diode to a ham RF transmitter for 432MHz. It consisted of an impedance matching network and a fast diode or two, plus a very simple bias network that used a D cell I think. The Tx ran 10-20W into the air cooled diode. Peter -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam@spam@mitvma.mit.edu with SET PICList DIGEST in the body

On Tue, 9 Jul 2002, Peter L. Peres wrote: > >In theory, about c/(2*lambda) Hz (== Bauds in this case). In practice, as >much as you can drive the device to. Diodes for high data rates have >special design (like controlled impedance feeds and such). I once had a >book that showed how to interface a laser diode to a ham RF transmitter >for 432MHz. It consisted of an impedance matching network and a fast diode >or two, plus a very simple bias network that used a D cell I think. The Tx >ran 10-20W into the air cooled diode. The actual limit is lower than I implied, the modulation is deteriorated by the decay time of the intermediary laser levels (the non-lasing transitions). However frequency-modulated lasers apparently do not have this limit ? Peter -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

On Tue, 9 Jul 2002, Peter L. Peres wrote: > In theory, about c/(2*lambda) Hz (== Bauds in this case). In practice, as > much as you can drive the device to. Diodes for high data rates have > special design (like controlled impedance feeds and such). I once had a > book that showed how to interface a laser diode to a ham RF transmitter > for 432MHz. It consisted of an impedance matching network and a fast diode > or two, plus a very simple bias network that used a D cell I think. The Tx > ran 10-20W into the air cooled diode. and later added: > The actual limit is lower than I implied, the modulation is deteriorated > by the decay time of the intermediary laser levels (the non-lasing > transitions). However frequency-modulated lasers apparently do not have > this limit ? I thought really high data rates used external (electro-acoustic?) modulators. -- Dave Tweed -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam.....mitvma.mit.edu with SET PICList DIGEST in the body

{Quote hidden}> -----Original Message----- > From: Dave Tweed [SMTP:EraseMEpicspam_OUTTakeThisOuTDTWEED.COM] > Sent: Wednesday, July 10, 2002 1:12 AM > To: PICLISTspam_OUTMITVMA.MIT.EDU > Subject: Re: [OT]: About smart dust and more > > On Tue, 9 Jul 2002, Peter L. Peres wrote: > > In theory, about c/(2*lambda) Hz (== Bauds in this case). In practice, > as > > much as you can drive the device to. Diodes for high data rates have > > special design (like controlled impedance feeds and such). I once had a > > book that showed how to interface a laser diode to a ham RF transmitter > > for 432MHz. It consisted of an impedance matching network and a fast > diode > > or two, plus a very simple bias network that used a D cell I think. The > Tx > > ran 10-20W into the air cooled diode. > > and later added: > > The actual limit is lower than I implied, the modulation is deteriorated > > by the decay time of the intermediary laser levels (the non-lasing > > transitions). However frequency-modulated lasers apparently do not have > > this limit ? > > I thought really high data rates used external (electro-acoustic?) > modulators. > They do mostly. You can achive 10Gbps through a direct modulated laser, but chirp really limits your link length due to dispersion. For lower dispersion, EA (Electro-Absorbtion) and MZ (Mach-Zender) modulators are used with a CW laser source. At 40Gbps it's pretty much mandatory have have an external modulator. Interestingly both of these external modulators can be configured to give negative chirp, so that performance over a long length of fibre can actualy be better than a short length. Frequency modulated lasers have been under a good deal of research. There are several benefits, but one big negative which is the increased complexity of the receiver. Regards Mike -- http://www.piclist.com hint: To leave the PICList @spam@piclist-unsubscribe-requestKILLspammitvma.mit.edu