The four members of the SDM4 MCF MSA—AFL, Corning Inc., Sumitomo Electric Industries Ltd., and TeraHop PTE—announced on September 17 the completion of the SDM4 Multicore Fiber Multi-Source Agreement (SDM4 MCF MSA) and the public release of the SDM4 Multicore Fiber MSA Technical Specifications, Version 1.0.

“This specification establishes a common technical foundation that can help accelerate adoption of multicore fiber across the industry,” said Antonio Castano, chair of the SDM4 MCF MSA. “By aligning around a shared four-core fiber design, we are enabling interoperability while supporting the increasing connectivity demands of AI data centers and campus networks.”

The specification defines common geometrical, optical, mechanical, and measurement requirements for a four-core multicore fiber intended for AI data centers, campus networks, and other short-reach optical links.

By reaching agreement on a common fiber specification, the participating companies have completed the objective established for the MSA: to provide an industry-defined technical foundation for multi-vendor interoperability and future international standardization of four-core multicore fiber.

The MSA includes the following definitions and specifications.

• A four-core, square-lattice 2x2 core arrangement with a core pitch of 40 ± 1µm
• A nominal cladding diameter of 125 µm
• Optical characteristics suitable for O-band short-reach applications
• Crosstalk limits of -40 dB or less at 1km and 1310 nm for both adjacent and diagonal core pairs

The specification also provides measurement principles and informative guidance on core numbering, rotational alignment, polarization mode dispersion, and marker configurations.

“The continued scale-out of AI infrastructure is increasing the number and density of optical connections required within data centers and across data center campuses,” the members said in a collective statement announcing the completion of the specification. “Multicore fiber can provide multipole independent optical paths within a standard fiber cladding, offering a potential path toward greater connection density.

“With the publication of the specification, the SDM4 MCF MSA establishes a stable, industry-aligned technical baseline for interoperable SDM4 multicore fiber,” the group continued. “The specification is intended to serve as a durable foundation for multi-vendor implementation, industry adoption, and related standards-development activities. Consistent with its role as a stable industry reference, frequent revisions to the MSA specification are not anticipated. Future evolution of requirements for this class of fiber is expected to be advanced through relevant international standards-development organizations, informed by the published specification.

“The publicly available specification may serve as a technical reference and foundation for discussions on multicore fiber standardization within ITU-T and IEC, and as a technical reference for discussions on optical transceiver and interface standardization by organizations such as IEEE.”

The document, SDM4 Multicore Fiber MSA Technical Specifications, Version 1.0, is available from each member of the MSA: AFL, Corning, Sumitomo Electric, and TeraHop.

You can download the specification here.