Digital Self-Homodyne Detection

This letter proposes and experimentally demonstrates a novel digital self-homodyne detection (DSHD) receiver for low-cost coherent detection of high-order modulation formats. The proposed approach is demonstrated for detection of 4-GBd quadrature phase shift keying, 16-quadrature amplitude modulation (QAM), 32-QAM, and 64-QAM signals with combined linewidths from 630 kHz up to 5.7 MHz without the need for optical filtering and polarization alignment. We describe the structure of the DSHD digital signal processing before evaluating the receiver performance in back-to-back, after single-span fiber transmission with both single-channel and multichannel transmitters, and after multispan transmission in a recirculating loop using a single channel. These results show that DSHD outperforms intradyne detection in the presence of fiber nonlinearity for QAM modulation formats of order 16 and higher.