DVD laser and photodiode

[Rene Tschaggelar]

Winfield Hill wrote:

Not my next step - one of our scientists will be using it to evaluate
nanowire FETs.

The circuit I posted (and you wrote up) doesn't look much like a
typical laser driver or optical receiver circuit, certainly not like
most of the ones I design. The primary goal throughout, which you
didn't show or analyze on your little writeup, it to maintain a very
clean 50-ohm impedance at all points for the drive signal and for the
received signal, and double terminated as well. As I mentioned, when
one of us attempted to translate the lashup to a PCB, the performance
dropped from 1200MHz to 600MHz despite being very careful, indicating
the important of avoiding any impedance discontinuities.

There are laserdiode drivers at Analog Devices doing 1.25 to 10GBit.
Yes, at some point, impedance drops towards the laser.

Rene