Dual Polarization In-phase and Quadrature High Speed Submarine Transmission with Only Two Photodiodes, ADC, MZM and DAC

As coherent optical communications industry moves to bitrates per carrier of 400 Gb/s and beyond, opto-electronics components with ever-increasing bandwidth and sampling rate become available. Based on these high-speed components, we propose a simplified transmitter and receiver architecture enabling the reduction of components to only two photodiodes (PD), two analog-to-digital converters (ADC), two Mach-Zehnder modulators (MZW) and two digital-to-analog converters (DAC). This simplified transmitter and receiver architecture is capable of generation of typical dual polarization (DP) signals with amplitude and phase modulation and detection of these signals with standard coherent signal processing algorithms. Compared to "standard" requiring four DAC and four MZM and receivers requiring four balanced PD and four ADC, our approach reduces the number of the mentioned components by roughly a factor of two at the expense of higher bandwidth and sampling rates for similar transmission speeds. We experimentally demonstrate this simplified transponder with generate DP 31.2 GBd signals using quadrature phase shift keying (QPSK), 8-ary quadrature amplitude modulation (8QAM) and 16QAM, achieving bitrates of 100 Gb/s, 150 Gb/s and 200 Gb/s, respectively. Finally, these signals are propagated over an ultra-long distance link and we achieve submarine-class distances beyond 6000 km for DP-QPSK and DP-8QAM.