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Entry  Mon Mar 22 15:01:24 2010, Dmass, Laser, ISS, ISS Spectra ISSILandOL.pdfGreenPDsBudget.pngIRPDsBudget.pngPDSubtracAll.pdf
    Reply  Tue Mar 23 15:01:29 2010, Dmass, Laser, ISS, ISS Spectra SubtractTestCoh.pdfSubtractTest.pdf
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                Reply  Wed Mar 24 22:12:49 2010, Mott, Laser, ISS, fb0 error 
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    Reply  Thu Mar 25 02:06:53 2010, Dmass, Laser, ISS, ISS Spectra 
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             Reply  Thu Mar 25 14:16:32 2010, Dmass, Laser, ISS, MZ Spectra! rawdata.zipLockedPhaseNoise.pdf
Message ID: 690     Entry time: Mon Mar 22 15:01:24 2010     Reply to this: 698   705
Author: Dmass 
Type: Laser 
Category: ISS 
Subject: ISS Spectra 

Hartmut is trapped down here in the ATF. I took some Spectra showing how my ISS is sensitive to air currents.

MY ISS IL PD is a pickoff of the transmission through the back of the PMC

MY ISS OL is one of my MZ readout PDs with one arm blocked.

The rest of this post is dedicated to: trying to figure out what is going on in this plot (the bottom phase noise spectrum)

We looked at a few things:

1) The PD signals themselves

  • What are the various signal and noise levels now...
  • Raw Voltage spectrum (of the free running Mach Zehnder..."phase noise"
  • Spectrum with 1 arm  blocked - this is about a factor of 2 lower because of the power loss
  • Dark Noise
  • The excess noise in the IR PDs (see 3rd plot below) was solved by some cable rearrangement at the breadboard. :(

2) Subtraction of the PD signals, IR and green - THERE IS LOTS OF INFORMATION ON THIS PLOT:

  • The one arm blocked state - the subtraction here should place a limit on the best SNR I can get assuming my software contrast defect compensation and balancing are perfect.
  • The PD signals in the free running state - subtraction here may say something about what my real obtainable SNR is for phase noise measuring, but interpreting requires more thought
  • The PD signals of opposite color in the free running state - this should reflect what my limit on phase noise subtraction is. (inherent in these plots is the coherence of the signals - it's     1-(Subtraction/Raw Data)^2 = Coherence).

I would like to point out that the PD signals of opposite have the same lack of coherence (and thus lack of subtraction) that we see in the phase noise measurement itself. The strange thing (which I don't understand) is why, with a phase noise signal above the intensity noise, we don't see coherence between the different color PDs.

 

 

Attachment 1: ISSILandOL.pdf  78 kB  Uploaded Mon Mar 22 16:03:11 2010  | Hide | Hide all
ISSILandOL.pdf
Attachment 2: GreenPDsBudget.png  68 kB  Uploaded Mon Mar 22 20:46:46 2010  | Hide | Hide all
GreenPDsBudget.png
Attachment 3: IRPDsBudget.png  69 kB  Uploaded Mon Mar 22 20:47:04 2010  | Hide | Hide all
IRPDsBudget.png
Attachment 4: PDSubtracAll.pdf  208 kB  Uploaded Tue Mar 23 04:17:41 2010  | Hide | Hide all
PDSubtracAll.pdf
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