Sumitomo Electric

Overview

Sumitomo Electric (SEI) is a Japanese conglomerate with a major fiber optics division operating as Sumitomo Electric Lightwave. In the context of AI data center interconnect, SEI is a leading developer of multi-core fiber (MCF), which packs multiple independent fiber cores into a single 125µm cladding — the same outer diameter as conventional single-mode fiber. This allows existing connector form factors to carry proportionally more parallel channels, directly addressing the GPU density-driven fiber strand count explosion in AI server racks. SEI drove the multi-source agreement (MSA) standardization of 4-core MCF, finalized in April 2026.