Sort of. We are able to shape these spectra now to improve the spectral efficiency (when using colorless muxing). The next generation of coherent modems will

Sort of. We are able to shape these spectra now to improve the spectral efficiency (when using colorless muxing). The next generation of coherent modems will have a 25G granularity and SW will tune the modem to maximize capacity for a given reach. Higher order modulation requires more SNR so this is the real limitation. For relatively short reaches the modulation order will increase. This improves the spectral efficiency. For longer reaches lower order modulation will be needed but the baud rate can increase. We can can however use other wavelength bands like L band to double the capacity. You are already seeing this in new submarine cables.