Hi Danny
you piqued my curiosity, it seems nice device
I took a look at the FX-5500 specs

I see:
Tx Power 16dBm
single bandwidth selectable 1250MHz
modulation is 4QAM-32QAM
BSPK1 and BPSK2(is a coding ratio on data or a downshift in symbol rate?)
single traffic port
2000-5000Gbps

what modulation correspond the 93dBm system gain you declared?

thx