On Fri, 29 Mar 2013 17:20:35 -0700 ed breya <[email protected]> wrote:
> I don't think that you can effectively directly mix two laser > wavelengths in a semiconductor light detector and get a useable IF - > it's hard enough just to get the tens of GHz modulation signals out > above the noise floor, let alone a tiny difference signal between > hundreds of THz. Well, i'd like to stay at 7GHz. That should be doable. At least i have read at least a dozen papers who claim to have done that. Some even from the 80s. > My knowledge of this stuff isn't up to date - maybe nowadays there > are detector devices and methods that take care of this directly, but > I don't think so. According to some papers i've read, just pointing two lasers at a photodiode will do that. Most of those around 800nm do offsets of a couple 10MHz to a few 100MHz at most. The ones with the larger offsets are usually in the 1-1.5um region and talk about applications for long haul highspeed communication. > Most really high speed diodes are optimized for the 1550 nm region > where EDFAs work, but maybe they have usable response at other > ranges. It depends on your particular application and wavelength. I > think detectors are usually specified over the entire IR region, so > datasheets may tell enough. Wavelenght is 780-800nm which is outside of the detection range of those communcation photodiodes. > > Here's link to some good info, but not current state of the art: > > http://e-collection.library.ethz.ch/eserv/eth:28429/eth-28429-02.pdf Thanks. I have read this already. I thought about trying to contact the author, and ask him a few questions about this project. > There are various methods that use lower frequency modulation > techniques so that regular detectors can be used directly. If you > study up on related patents, you may find some ideas and leads to > appropriate actual devices. I have not come accross any that seemed simpler. Can you give me some pointers? Attila inali -- The people on 4chan are like brilliant psychologists who also happen to be insane and gross. -- unknown _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
