We revisited the squeezer TTFSS with the new FSS settings described in alog 65236 which should fix the 2.5MHz line discovered in alogs 64653 and 64649. With a FSS common gain of 11dB and a fast gain of 8dB the 2.5MHz was still visible but with a 20dB lower amplitude. This allowed us to get back to the old squeezer TTFSS settings and lock with the EOM.

Playing with the FSS common and fast gain, there is a strange effect where lowering the common gain with the old fast gain of 11dB makes the 2.5MHz disappear completely but a peak at 160kHz will appear instead. The later is probably a PZT resonance. Lowering the fast gain will then make the 160kHz peak disappear but the 2.5MHz peak will again appear—albeit at a lower amplitude.