Multipath Interference Impact Due to Fiber Mode Coupling in C+L+S Multiband Transmission Reach

Multiband transmission is, nowadays, being implemented worldwide to increase the optical transport network capacity, mainly because it uses the already installed single mode fiber (SMF). The G.654E SMF, due to its attributes, e.g. low-loss, and large-effective area in comparison with the standard G.652 SMF, can also increase network capacity and can also be used for MB transmission. Nevertheless, in MB transmission power mode coupling arises when bands with wavelengths below the cut-off wavelength are used, inducing multipath interference (MPI). This work investigates the impact of the MPI, due mode coupling from G.654E SMF, in the transmission reach of a C+L+S band transmission system. Our results indicate that for the S-band scenario, the band below the wavelength cut-off, an approximately 25% reach decrease is observed when the MPI/span increases to -26 dB/span considering quadrature phase-shift keying (QPSK) signals with a 64 GBaud symbol rate. We also concluded that if the L-band were not above the wavelength cut-off it would be much more affected than the S-band, with an approximately 55% reach decrease due to MPI impact.