(Sheila, Alexa)

1. We wanted to re-visit the EX PLL shot noise measurement we had previously done.

• From the direct output of the pre-ampifier we measured the beatnote signal to be -33dB at 39.8MHz with 100 Hz BW
• The RF spectrum analyzer had a noise floor of -126dbm with 100 Hz BW (no attenuation)
• From the direct output of the pre-amp with the BBPD blocked, we measured an electronic noise of -118dbm at 100 Hz BW from the PD
• With the fiber blocked we measured noise of -114dBm at 100 Hz BW
• We meaured the power at the BBPD to be 5.8mW with a DC reading of 1.04V --> .52mA at the PD. We calibrated the PD responsivity to be .09 A/W
• To confirm we were measuring shot noise, we increased the optical power by a factor of 2, and saw that the noise with the fiber blocked increased to -111dBm at 100 Hz BW. We expected this increase, so are confident we were measuring shot noise.

2. WIth the EX PLL locked, the arm cavity well aligned, and the green beam flashing, we looked at the PDH error signal out of the demod IMON and measured the peak-to-peak of the signal to be 230mVpp

3. We went on to investigate the fringe wrapping we saw in the PDH amplitude spectrum at the error point. With the arm locked, we only saw a slight difference in the spectrum with the HEPA fans on or off (Sheila will attach pictures). There did not seem to be fringe wrapping, and the acoustic noise seemed minimal. I will look at the PDH shot noise again when I can misalign ITMX and see if the fringe wrapping is still there..