“…Line codes reshape the transmit spectrum introducing a spectral null at DC in the signal, matching the one existing in the channel, while QFB uses the detected symbols to estimate and subtract the BLW component from the received signal. These techniques have been proposed for many different baseband or homodyne systems such as magnetic recording (e.g., [5]- [8]), wireless channels (e.g., [3], [4], [9], [10]), twisted pairs (e.g., [11], [12]), and optical fiber links (e.g., [13], [14]). However, as we shall show in this paper, these proposals are not sufficient to compensate BLW in coherent receivers where the carrier frequency offset between the received signal and the local oscillator (LO), is different from zero (e.g., intradyne or heterodyne detectors).…”