Corning and partners complete SDM4 multicore fiber MSA

On 17 September 2026, Corning Incorporated, AFL, Sumitomo Electric Industries, and TeraHop announced the completion of the SDM4 Multicore Fiber Multi-Source Agreement. The participating companies publicly released the SDM4 Multicore Fiber MSA Technical Specifications, Version 1.0.

The document defines geometrical, optical, mechanical, and measurement standards for a four-core optical fiber. The design is intended for AI data centers, campus networks, and other short-reach links operating in the O-band.

Technical requirements established in the agreement include a 2×2 square-lattice core arrangement with a core pitch of 40 ± 1 µm. The specification limits optical crosstalk to −40 dB or less at 1 km and 1310 nm across both adjacent and diagonal core pairs. It also details guidelines for core numbering, rotational alignment, polarization mode dispersion, and marker configurations.

The group does not anticipate frequent revisions to the document. Instead, the specification is designed to serve as an industry reference for multi-vendor interoperability and to inform ongoing standardization discussions within ITU-T, IEC, and IEEE.