We have a customer who wants us to generate some fast pulse-type timing signals and run them around a big machine. The longest run will be around 150 feet, and he wants sub 1 ns resolution on pulse timings and widths, and below 100 ps RMS jitter.
So we measured some CAT6A and coax cables.
ftp://jjlarkin.lmi.net/DDG_cables.zip
Note the characteristic "drool" step responses one gets from a lossy transmission line. As expected, the 10/90 rise time goes as the square of the cable length. Good coax is much better than CAT6.
None of this looks promising. Coax is faster, but is still slow and will have ground loop problems. We want DC coupling, so transformers are out.
Anybody who gets 10Gbit ethernet through CAT6 must be doing some very serious adaptive equalizing. We could equalize CAT6, but that would be a nasty mess.
Looks like we should go fiber. We'll probably need to run 16 signals
150 feet, so we'll need 16 laser/pin diode sets and 16 fibers, or maybe look into the MPO or MTP fiber ribbon cable things, if we can find the driver/receiver things for the ends.Another nuisance is that most tosa/rosa gadgets assume telecom type apps, with AC coupled laser drivers and agc/AC coupled receivers, which don't work with baseband timing pulses.
John