Coded Eight-Dimensional QAM Technique Using Iterative Soft-Output Decoding and Its Demonstration in High Baud-Rate Transmission

We proposed coded eight-dimensional (8-D) quadrature amplitude modulation (QAM) and experimentally demonstrated in high baud-rate transmission. Both high baud rate and multilevel modulation techniques are necessary for large capacity long haul transmission without increasing the number of transponders. However, optical signal-to-noise ratio (OSNR) tolerance of higher order modulation is low due to the short minimum Euclidean distance. Therefore, to relax OSNR tolerance by enlarging minimum Euclidean distance, we proposed 8-D modulation formats. The spectral efficiency of the proposed coded 8-D-16QAM, 8-D-32QAM, and 8-D-64QAM is equivalent to polarization division multiplexed (PDM)-8QAM, PDM-16QAM, and PDM-32QAM, respectively. To confirm the applicability of the proposed 8-D modulation to high baud rate transmission, we experimentally demonstrated 96-GBaud 8-D-16QAM wavelength division multiplexed transmission over 5,-252 km using iterative soft output decoding. The line data rate is 576-Gbps and a net rate 478-Gbps. At the same spectral efficiency, 8-D-16QAM using iterative soft output decoding can expand the transmission reach by 1212 km compared to conventional PDM-8QAM.