Design of an all-fiber mode power splitter for mode-division-multiplexing transmission.

An all-fiber mode power splitter (MPS) for mode-division multiplexing (MDM) transmission is proposed and numerically investigated. The MPS is based on the configuration of the symmetric few-mode fiber (FMF) coupler, with the operation of four modes (, , , and ). By comprehensively optimizing the FMF coupling parameters, including both the coupling area distance and the coupling length , MPSs with various power splitting ratios from 90%:10% to 50%:50% under the condition of different single guided mode injection are obtained. Then, the MPS with a 90%:10% power splitting ratio under the simultaneous injection of , , , and modes is reported, which can be used as the mode tap for the optical performance monitoring. Moreover, based on the proposed MPS structure, selective mode power strippers with more than 25 dB mode extinction ratio for , , , and modes are numerically verified. The arbitrary single guided mode arising in the FMF can be selectively coupled into another FMF, together with an insertion loss of less than 1 dB. Owing to the flexible setting of the mode power splitting ratio, the proposed MPS may become a potential solution to realizing system performance monitoring and mode power routing in MDM systems.