Ultracompact and Low Crosstalk Multicore Fiber Fan-in/out Device Fabricated via 3D Nanoprinting

As an optical transmission medium for high-density channels, a multicore fiber (MCF) is being increasingly utilized to enhance the communication capacity of modern systems. The MCF connecting module, also known as the fan-in/fan-out (FIFO) device, is a critical component in these applications. However, the current generation of FIFO devices, typically millimeter-sized, poses challenges for integrating multicore fiber systems seamlessly. In this work, we design and fabricate a 7-channel FIFO device using 3D nanoprinting, exhibiting an insertion loss of 1.72 dB and intercore crosstalk of less than −61.21 dB, with an average insertion loss of 2.23 dB in the C+L band. Remarkably, by utilizing the properties of a 3D printing photonic structure with a high refractive index contrast and the principle of total internal reflection, we achieve efficient and flexible control of the photon propagation direction, significantly reducing the overall size of the device. The total FIFO device has a compact length of just 140 μm. Additionally, the transmission of higher-order modes has also been successfully achieved based on the designed waveguide. The proposed compact FIFO device features low loss, low crosstalk, and broadband capabilities, offering a high-density integration solution for 3D optical interconnection schemes.