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Entry  Tue Dec 7 11:11:37 2021, aaron, Noise Hunting, Laser, finding a stable lock 
    Reply  Tue Dec 7 11:44:27 2021, rana, Noise Hunting, Laser, finding a stable lock 
       Reply  Fri Dec 10 11:30:44 2021, shruti, Update, Laser, Beat between the lasers beat.pdffiberbox.pdf
Message ID: 2832     Entry time: Tue Dec 7 11:44:27 2021     In reply to: 2831     Reply to this: 2833
Author: rana 
Type: Noise Hunting 
Category: Laser 
Subject: finding a stable lock 
  1. check to see if the 140 kHz noise is on the laser already. Post spectrum of beatnote in ELOG.
  2. Check error signal of cavity with a beam block placed inside the cavity. This allows the reflected beam to still hit the PDH PD to check for electronics pickup, but there is no cavity signal.
  3. Check error signal with beam to REFL PD blocked. also post to ELOG.
  4. Let's discuss about the 50 Ohm termination stuff. Generally, the 50 Ohm or not issue is not critical in these applications where the signal is mostly less than 2 MHz (after demodulation); the wavelength for 2 MHz in cable is ~(c*2/3)/(2 MHz) ~ 100 m. The main purpose of checking impedances is to make sure that the sources can drive the load, whether its 1 Mohm, 50 ohm, or 25 ohm. So it would be fine to have a T going to a 1 Mohm scope input.
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