Low-loss C-band all-fiber FIFO device by novel bridge fiber.

• Reveal the design principles of trench-assisted bridge fibers (TABFs), offering an effective methodology for fabricating TABFs for FIFO devices. • Demonstrate the feasibility of utilizing TABFs for fabricating low-loss FIFO devices. • The results indicated that the fabricated FI/FO device exhibited a remarkably low loss (<0.50 dB), and relatively low crosstalk (<-55.2 dB) in the C-band. Multi-core fibers (MCF) technology is the feasible path to extend the capacity of optical fiber communication systems. However, there is a lack of low-loss and low-crosstalk multi-core fan-in and fan-out (FIFO) devices for MCF communication in the C-band. In this paper, we proposed all-fiber FIFO devices with seven trench-assisted bridge fibers (TABFs). The special structure of the TABFs could facilitate the matching of single-core fiber with MCF during the tapering progress. By using the TABFs, the average taper loss was less than 0.06 dB. The novel method can reduce the insertion loss of FIFO devices. The experiments indicated that the fabricated FIFO devices exhibited lower than 0.50 dB insertion loss and less than −55.2 dB crosstalk in the C-band. This work provides novel TABFs and an efficient way to fabricate low-loss low-crosstalk FIFO devices for MCF communication systems. [ABSTRACT FROM AUTHOR]