Optimization of Spatial Aperture-Sampled Mode Multiplexer for a Three-Mode Fiber

An optimization procedure for spatial mode multiplexing from individual single-mode fibers into a three-mode fiber based on a spatial aperture sampling concept has been developed. By placing space-variant imaging elements between the single-mode and few-mode fibers, each beam aperture can be shaped for lower loss coupling and low mode-dependent losses. The optimization achieves a record theoretical -1.5-dB insertion loss, improving on the previous theoretical -2-dB record.