We show successful transmission of 45.8-Gb/s and 125-Gb/s coherent-detected polarization-multiplexed quadrature phase-shift keying (CP-QPSK) over both 2054 km and 4108 km of 10-Gb/s non-return to zero (NRZ) 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 co-propagating WDM channels placed on a 100-GHz and on a 50-GHz grid, where we optimized the transmission performance by sweeping the launch power and pre-compensation. For 45.8-Gb/s CP-QPSK a margin with respect to the 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 dBQ with respect to the FEC-limit is reported. This underlines the great robustness of CP-BPSK towards nonlinear fiber impairments and thereby the feasibility to cross trans-oceanic distances with this modulation format.