40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log  Not logged in ELOG logo
Entry  Fri Jul 12 12:51:13 2013, Charles, Update, ISS, RMS Noise from PMC Transmission 
    Reply  Fri Jul 12 13:15:43 2013, Koji, Update, ISS, RMS Noise from PMC Transmission 
       Reply  Fri Jul 12 18:30:20 2013, Charles, Update, ISS, RMS Noise from PMC Transmission 
Message ID: 8836     Entry time: Fri Jul 12 12:51:13 2013     Reply to this: 8838
Author: Charles 
Type: Update 
Category: ISS 
Subject: RMS Noise from PMC Transmission 

I went out on the floor to look at the transmitted signal from the PMC to get a rough idea of the noise of the unstabilized laser. There was already a scope hooked up so I just used the measurement features to find the following:

Signal average = 875 mV.  Peak-to-Peak noise = 45 mV

Assuming the noise can be approximated as Gaussian noise, the heuristic for converting to RMS noise of the signal is RMS = Peak-to-Peak / 8 (or Peak-to-Peak / 6, I've used both...)

-> RMS Noise ~ 6.5 mV

When designing my filtering stages and RMS detection/triggering, I'll use relative RMS, i.e. 6 mV / 875 mV = 0.007, as a measure of unstabilized laser noise.

ELOG V3.1.3-