PMD Impact on MCF Submarine Cables: Reassessing Outage Performance of Transmissions

In this study, we designed and fabricated a cable accommodating 4-core and 7-core multicore fibers (MCFs). Fiber characteristics including attenuation, dispersion and polarization mode dispersion (PMD) during the cabling procedure were measured and analyzed. We observed a significant degradation in PMD for MCFs, particularly for those outer cores proximate to the cladding. Thus it requires longer taps of MIMO equalizers to sufficiently equalize at the receiver for reliable communications at the subsea distance. To assess the PMD impact on outage performance with limitations of MIMO equalizers’ taps, we developed a C-band 8000-km submarine transmission model which was calibrated with measured parameters during cabling, for qualifying 4- and 7-core MCFs in practical use. Simulations performed on the calibrated model could predict the outage performance for ensuring the communication reliability. More than 2-dB SNR margin is required to prevent the PMD-induced outage with using 300-taps MIMO equalizer at the receiver. Based on these comprehensive tests and simulations, we emphasize the importance of carefully managing PMD and ensuring adequate system SNR margins during the practical cabling and deployment of optical MCFs submarine cables.