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Entry  Mon Mar 29 21:43:27 2010, Alberto, Configuration, PSL, Reference Cavity PD Noise Spectrum 2010-03-29_FSS_PD_shotnoise_and_darknoise.png2010-03-29_FSS_PD_shotnoise_and_darknoise.png
    Reply  Tue Mar 30 06:37:32 2010, rana, Configuration, PSL, Reference Cavity PD Noise Spectrum rc.png
       Reply  Wed Mar 31 15:31:53 2010, steve, Update, PSL, Reference Cavity RF PD base upgraded brspdbs.JPG
    Reply  Sat Apr 3 11:35:47 2010, rana, Configuration, PSL, Reference Cavity PD Noise Spectrum 
       Reply  Sat Apr 3 16:07:40 2010, Alberto, Configuration, PSL, Reference Cavity PD Noise Spectrum 2010-03-29_FSS_PD_shotnoise_and_darknoise.png
          Reply  Tue Apr 6 11:27:11 2010, Alberto, Update, Computer Scripts / Programs, Data formats in the Agilent AG4395a Spectrum Analyzer 
             Reply  Tue Apr 6 16:55:28 2010, Alberto, Update, Computer Scripts / Programs, Data formats in the Agilent AG4395a Spectrum Analyzer 
Message ID: 2759     Entry time: Sat Apr 3 11:35:47 2010     In reply to: 2732     Reply to this: 2760
Author: rana 
Type: Configuration 
Category: PSL 
Subject: Reference Cavity PD Noise Spectrum 

The units on this plot are completely bogus - we know that the thermal noise from the resonant part of the circuit is just V = sqrt(4*k*T*Z) ~ 3nV/rHz. Then the gain of the MAX4107 stage is 10. The output resistor is 50 Ohms, which forms a divide by 2 with the input impedance of the spectrum analyzer and so the bump in the dark noise should only be 15 nV/rHz and not microVolts.

Quote:

[Rana, Alberto]

This evening we measured the noise spectrum of the reference cavity PD used in the FSS loop. From that we estimated the transimpedance and found that the PD is shot-noise limited. We also found a big AM oscillation in correspondence of the FSS modulation sideband which we later attenuated at least in part.

This plot shows the spectrum noise from the RF output of the photodetector.

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