40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  ATF eLog  Not logged in ELOG logo
Entry  Sat Mar 12 05:32:40 2011, Zach, Laser, GYRO, current gyro noise gyro_noise_with_contribs_3_11_11.pngoutput_box.pnginput_box.png
    Reply  Sat Mar 12 16:11:35 2011, Koji, Laser, GYRO, current gyro noise 
       Reply  Sat Mar 12 16:22:53 2011, Zach, Laser, GYRO, current gyro noise 
          Reply  Sat Mar 12 19:20:19 2011, Koji, Laser, GYRO, current gyro noise 
             Reply  Sat Mar 12 21:24:14 2011, Zach, Laser, GYRO, current gyro noise OLTFs_3_11_11.png
                Reply  Sun Mar 13 00:27:29 2011, Koji, Laser, GYRO, current gyro noise 
Message ID: 1349     Entry time: Sat Mar 12 19:20:19 2011     In reply to: 1348     Reply to this: 1350
Author: Koji 
Type: Laser 
Category: GYRO 
Subject: current gyro noise 

I understand your explanations. Now I feel these points.

- This AOM feedback should agree with the calibrated error signal of the secondary cavity.  This is not confirmed.

- This noise is suppressed by the loop gain of the secondary cavity. (The spillover noise of the secondary.) This is not shown. Also the OLTF of the secondary is not shown.

- The AOM feedback at around 100Hz shows the same level as the primary spillover. Does this suggest that the loop gain of the secondary is higher than 1k???

- Of course we like to see the OLTF of the PLL.

Are you working with the measurements, Zach?

Quote:

This is the answer I would give:

  • The magnitude is lower because the differential noise of the input optics is suppressed by the secondary (CW) loop gain in the PLL readout (but not in the AOM readout). This was the main advantage to this readout scheme in the first place (see this post)
  • The shape above ~100 Hz is different either because the residual primary loop noise ("spillover noise") is also suppressed in the PLL readout OR because the PLL bandwidth is lower than this. We don't have an OLTF of the PLL yet, but we can see which one it is by carefully reviewing the diagram in the above post to see if the spillover noise should indeed be suppressed (we didn't think it would).

 

ELOG V3.1.3-