Design and demonstration of a multicore single-mode fiber coupled lens device

A graded index micro-lens at the end face of a four cores multicore single-mode fiber has been developed. In this paper, the use of a section of graded index multimode fiber at the end face of a four cores multicore fiber are discussed. The device design and its experimental demonstration are discussed. This compact coupling solution (the 125 μm external diameter is preserved) allows to relax tolerances of alignment with an expansion ratio of 7.4. The 10.5 μm beam diameter of each core of the multicore fiber is collimated to a large Gaussian mode field diameter of 78 μm. An average value of coupling efficiency of 1.2 dB between two diagonal cores in front of a mirror is measured.