Keita, Evan

We went in and removed the couplers between the EOM driver and the EOM (see 23472), as well as the extra phase delay cable on the ISC rack which was being used to match the coupler-induced delay.

Removing the couplers got rid of the extra noise on the 45 MHz OOL readback (see attachment).

Strangely, putting the couplers on the spare driver in the CER (which is terminated with a 50 Ω resistor, rather than an EOM) does not produce this extra noise (see attachment).

We have turned the spare driver back on and reconnected it to the digital system.