Micro-bend-Resistant Low-Differential-Mode-Group-Delay Few-Mode Fibers

We report the design of micro-bend-resistant low-differential-mode-group-delay (low-DMGD) few-mode fibers that support up to six mode groups (12 LP modes, 21 spatial modes) and that are adapted to multiple-input multiple-output mode-division-multiplexed transmissions. Compared to previous designs, the micro-bending sensitivity is reduced by more than a tenfold factor with acceptable impacts on attenuation, effective area, and DMGD for 2, 3, and 4 mode groups, but with some degradation for five and six mode groups. These fibers also exhibit low coupling between their mode groups, which is beneficial for DMGD compensation and multiple-input multiple-output processing. Based on these designs, we fabricate and characterize a 4-mode-group (6-LP-mode, 10-spatial-mode) fiber with a micro-bending sensitivity reduced by a factor up to 20 compared to previous realizations. This sensitivity is even lower than that of typical standard single-mode fibers, which should allow the deployment in most telecommunication networks without significant induced losses. A DMGD-compensated link with values <= 72 ps/km is also realized. Finally, we show that previous fibers with 5 and 6 mode groups already have low micro-bending sensitivities, which should prevent from using micro-bend-resistant designs which, in these cases, can degrade the attenuation, effective area and DMGD.