Zjs log: Difference between revisions

:It consists of two sections. There is a filter on the main laser driver line: two 820uH inductors as well as a 10uF cap and 3ohm resistor to ground. This is to prevent fast feedback from going back into the laser driver. Also, the low pass may clean up the laser driver output. The second section is the fast feedback branch. There are low pass and high pass branches, so the gain is actually less in the middle of the frequency range. From Larry: apparently you want to suppress the gain a tad in the middle as that's where the laser will naturally respond. The high frequency gain is to fix phase response, so that there is not too much phase accumulation at high freq. Also, he recommended the whole circuit being preceded by 10dB attenuator. I ended up putting in 16dB as that seemed to work well. It's interesting how you really don't need any gain in the fast feedback branch.

:The lock was much better when utilizing this fast feedback branch, the transmitted IR was very flat in output intensity, fluctuating less than 10%. Lock is a little more finicky, i.e. photodiodes seem to get unbalanced more frequently, this probably due in part to the 50inputs. Hopefully we're finally getting a handle on these issues.