Penalties from in-band crosstalk for advanced optical modulation formats

We quantify, through simulations and experiments at 21.4 GBaud, the effect of in-band crosstalk on several advanced optical modulation formats, showing a 1-dB penalty at a bit-error ratio of 1×10
^-3
from a crosstalk of -18 dB, -24 dB, and -32 dB for QPSK, 16-QAM, and 64-QAM, respectively.