Simultaneous Multi-Core Fiber-to-Fiber Self-Coupling With Near-Infrared Light-Induced Self-Written Optical Waveguide

Multi-core fibers (MCF) and multichannel optical waveguides have garnered significant attention as viable technologies for enhancing transmission capacity. However, the assembly of multichannel optical components encounters certain challenges, particularly in terms of alignment and takt time. To address these issues, this study proposed and demonstrated an optical coupling method using near-infrared (NIR) light-induced self-written (LISW) optical waveguide technology to simultaneously connect 4-core MCFs. All-solid LISW optical self-coupling between 4-core MCFs was achieved by employing an advanced selective polymerization process using light at 1310 nm wavelength. The resin used was characterized by the presence of an NIR dye in the monomer. The LISW optical waveguide core formation time was approximately 10 s, and the simultaneous 4-core formation was achieved within a short time. The average insertion loss (IL) of the all-solid LISW optical waveguide was 0.2 dB, and both the average IL of each channel and IL variation per channel were reduced compared with those of the butt joint. Thus, the LISW optical self-coupling compensated for the misalignment that occurred in the butt joint. Therefore, the LISW optical waveguide can also be used for the simultaneous optical self-coupling of multiple channels and is an effective method for reducing the fabrication time.