You should talk with the folks at https://eridan.io/product/ https://eridan.io/product/ . They're shipping[1] 16384 QAM and their scheme is a much more power a

You should talk with the folks at https://eridan.io/product/ https://eridan.io/product/ . They're shipping[1] 16384 QAM and their scheme is a much more power and bandwidth efficient than a linear amplifier. (In addition to the coding efficiency, they don't need guard bands.) [1] That page says "14 bits or more". I can't tell you how many bits "or more" they can do but it is non-zero.