A full multicore fiber optic link is demonstrated, transmitting greater than 100 Gb/s through a single strand of multimode fiber for the first time. The fiber, which consists of seven graded-index multimode cores, is used to transmit up to 120 Gb/s over 100 m using a custom multicore-fiber interfacing transmitter and receiver. 2-D arrays of vertical-cavity surface-emitting lasers (VCSELs) and vertically illuminated photodiodes (PDs) are fabricated with a geometry corresponding to the outer six cores of the seven-core fiber, which is arranged in a hexagonal pattern. Both flip-chip and wire-bonding technologies are used to package the VCSEL and PD chips with multichannel transmitter and receiver integrated circuits. Amplitude and timing margins of the end-to-end signals are analyzed through bit-error-rate (BER) measurements. The effects of electrical and optical crosstalk are shown to result in negligible degradation to the BER performance. © 2006 IEEE.