Dear friend!
As shown in the screenshot, the input optical power of the FD module is too high. You need to adjust the optical power of the RX of the FD.
OSC Optical Power Gear:
Gear 0(V-O-A=0dB), Gear 1(V-O-A=3dB), Gear 2(V-O-A=6dB), Default Gear
Default: Gear 0(V-O-A=0dB)
This parameter is supported when the G3OH20H board is interconnected with the G2AST4 board configured with the OSC module (not the single-fiber bidirectional module).
If your OH20H board is not interconnected with the G2AST4, this parameter cannot be adjusted. So you can try adding a fixed optical attenuator outside.
Thanks!