I can lock the laser frequency to RCAV with TTFSS, but the noise in the beat is higher than before.

 I'm trying to bring the beat back. This is the to do list

1) check the Power from LO input to match the designed value for TTFSS (10dB)

   The LO power available is 20 dBm

  The mixer, JMS-1H, requires 10dBm input. I used 10 dB Attenuator to attenuate the LO signal before plugging in the servo.

   I forgot to use the attenuator before. I'm not sure if the 20dBm signal will affect the RF amplifier and the others components or not. I might have to check the box again**.

2) check the error signal, make sure that the phase is right.

     To make sure that the box is working properly, I checked the error signal, the details are here. Since we changed the setup the phase adjustment between LO and PD needs to be changed. It is set to 5.3659 V to make the error signal symmetric.

3) optimize the gain, between common gain and fast gain. To minimize the noise from MIXER MON

     I adjusted common gain and fast gain while monitored the noise spectrum from MIXER MON from dc - 10 MHz to make sure that the noise was minimized and there was no oscillation at any frequency.

     COMMON GAIN knob is set to 455. FAST GAIN knob is set to 800.

4) Then I checked the beat signal. It is an order of magnitude higher than before.

The setup:

1mW power into both cavities

 RCAV gain: FAST 800, COMMON 455.

ACAV gain: 7