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Message ID: 15532     Entry time: Mon Aug 17 23:41:50 2020
Author: gautam 
Type: Update 
Category: BHD 
Subject: Whitening and air BHD dark noise 

Summary:

With the chosen transimpedance of 300 ohms, in order to be able to see the shot noise of 10 mW of light in the digitized data streams, we'd need all 3 stages of whitening. If we want to be shot noise limited with 1 mW of LO light, we'd need to increase said transimpedance I think.

Details:

The measurements were taken with

  1. No light incident on the DCPDs.
  2. The flat whitening gain was set to 0 dB.
  3. Whitening engaged sequentially, stage by stage, shown as (Blue, Red, Orange and Green) curves corresponding to (0, 1, 2, 3) stages of whitening.

Of course, it's unlikely we're going to be shot noise limited for any configuration in the short run. But this was also a test of 

  1. My soldering.
  2. Change of whitening corner frequencies.
  3. Test of the overall whitening board assembly.

All 3 tests passed.

Attachment 1: BHD_whitening.pdf  267 kB  Uploaded Tue Aug 18 00:42:21 2020  | Hide | Hide all
BHD_whitening.pdf
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