  Compact fiber-to-chip couplers play an important role in optical
interconnections, especially in data centers. However, the development of
couplers has been mostly limited to standard single mode fibers, with few
devices compatible with multicore and multimode fibers. Through the use of
state-of-the-art optimization algorithms, we designed a compact
dual-polarization coupler to interface chips and dense multicore fibers,
demonstrating, for the first time, coupling to both polarizations of all the
cores, with measured coupling efficiency of $-$4.3 dB and with a 3 dB bandwidth
of 48 nm. The dual-polarization coupler has footprint of 200 $\mu m^2$ per
core, which makes it the smallest fiber-to-chip coupler experimentally
demonstrated on a standard silicon-on-insulator platform.
