Spacing-Tailored Multicore Fiber Interface for Efficient FIFO Devices

Multicore fibers (MCFs) have attracted intense attention to overcome the capacity limit of single-core optical fiber communication system. However, as indispensable connection devices between the MCF and the individual single mode fiber (SMF), fan-in and fan-out (FIFO) devices are challenging to achieve overall performance in terms of coupling efficiency, crosstalk, return loss, and device compactness. Here we develop an MCF reverse-tapering technique to increase the core-to-core spacing of the MCF and construct a spacing-tailored interface between the MCF and the normal SMF bundle. The fabricated FIFO device for the small-core MCF with narrow core-to-core spacing of 35 mu m features a low average coupling loss (similar to 0.6 dB), extraordinarily low crosstalk (<-65 dB) and a return loss (<-60 dB) without using any bridge elements, where the remarkably low crosstalk is about 20 dB lower than using special bridge fibers for the same type of MCF. The flexibility of reverse tapering of MCFs can overcome its intrinsic integration challenge and provide a powerful approach to constructing all-fiber FIFO devices with compact construction and excellent overall performance.

Automated summary

Researchers developed a method using MCF reverse-tapering technique to construct fan-in and fan-out devices with improved coupling efficiency, reduced crosstalk, and return loss. Experimental results showed that this method achieved remarkably low crosstalk and return loss without using any bridge elements.