45.8 and 125 Gb/s CP-QPSK/CP-BPSK Field Trial Over Installed Submarine Cable

We show successful transmission of 45.8 and 125
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Gb/s coherent-detected polarization-multiplexed quadrature phase-shift keying (CP-QPSK) over both 2054 and 4108 km of 10 Gb/s nonreturn-to-zero-optimized field-deployed submarine cable. Moreover, we report successful transmission of 45.8 Gb/s coherent-detected polarization-multiplexed binary phase-shift keying (CP-BPSK) over 9420 km of legacy submarine fiber. We present single-channel transmission results, as well as wavelength-division multiplexed (WDM) transmission results with copropagating WDM channels placed on a 100 GHz and on a 50
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GHz grid, where we optimized the transmission performance by sweeping the launch power and precompensation. For 45.8
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Gb/s CP-QPSK, a margin with respect to the forward error correction (FEC) limit of 1.7 dBQ was obtained after transmitting over a 4108 km distance in a 50 GHz grid WDM configuration. Considering the transmission of 125 Gb/s CP-QPSK over the same distance and with the same channel configuration, a 1.1 dBQ margin was measured, showing the feasibility of a tenfold increase in transmission capacity over legacy submarine fiber. This significantly delays the costly alternative of deploying a new submarine cable. For the transmission of a 45.8 Gb/s CP-BPSK modulated signal on a 50 GHz WDM grid over a 9420 km distance, a margin of 1.2
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dBQ with respect to the FEC limit is reported. This underlines the great robustness of CP-BPSK toward nonlinear fiber impairments and thereby the feasibility to cross transoceanic distances with this modulation format.