The transition from copper to optical interconnects is moving beyond scale-out and into scale-up, with the near-term target of linking racks inside very large AIartificial intelligenceAI stands for artificial intelligence pods before optical links begin replacing copper within the rack itself. The direction of travel is increasingly clear: multi-wavelength optics per fiber, bidirectional transmission, and a migration path from pluggable transceivers to NPOnear-packaged opticsNPO denotes optical components placed very close to the package. and then CPOco-packaged opticsOptical devices and CPUs are integrated into a single package.
Today’s pluggable optical links are still dominated by single-wavelength implementations using two or four fibers. Pushing those designs to higher bandwidth would require faster, more power-hungry PHYphysical layer interfacePHY denotes the physical-layer interface of a data link.s or additional fibers, both of which raise cost. The economic pressure comes in part from connectors, which are more expensive than fibers, making bandwidth scaling through more fiber unattractive.
OCIOptical Compute InterconnectOCI is an optical interface effort aimed at enabling interoperable high-bandwidth links between systems.-MSAMulti-Source AgreementAn MSA defines a common specification that allows multiple vendors to build interoperable components., short for Optical Compute Interconnect Multi-Source Agreement, is positioned as an open and interoperable specification for AIartificial intelligenceAI stands for artificial intelligence scale-up. Founding members include AMD, Broadcom, Meta, Microsoft, Nvidia, and OpenAI. The group’s stated goals are cross-vendor compatibility, lower-power optical SerDes1. Serializer/DeserializerSerDes is the high-speed I/O block that receives, conditions, and retransmits the signal.2. Serializer-DeserializerSerDes converts parallel signals into serial data streams and back., and a multi-vendor supply chain that reduces integration risk and vendor lock-in.
The first generation of OCIOptical Compute InterconnectOCI is an optical interface effort aimed at enabling interoperable high-bandwidth links between systems.-MSAMulti-Source AgreementAn MSA defines a common specification that allows multiple vendors to build interoperable components. defines 8 channels per fiber, with 4 wavelengths in each direction. Each wavelength runs at 53.125Gbps NRZnon-return to zeroNRZ is a binary signaling scheme without return to zero between bits., with wavelengths spaced slightly more than 2nm apart. The reference link model is based on 500m of SMFsingle-mode fiberSMF denotes a single-mode fiber for optical transmission over longer distances.-28 fiber with 2.5dB total insertion loss, mostly from connector losses in the transceiver-to-transceiver path. After error correction and signaling overhead, the effective rate is 50Gbps per wavelength.
For an aggregate 200G bandwidth in one direction, OCIOptical Compute InterconnectOCI is an optical interface effort aimed at enabling interoperable high-bandwidth links between systems. in CPOco-packaged opticsOptical devices and CPUs are integrated into a single package format is presented as offering the best mix of low link power per bit and long reach among the compared options. It is also framed as delivering the reach of pluggables at roughly one-third the power of a pluggable transceiver, while keeping a roadmap for scalable bandwidth growth.
Future generations are being discussed in terms of more wavelengths per fiber, higher per-wavelength rates, dual polarization, and more advanced signaling such as PAM1. process application moduleSoftware-related method or tool for development, control or data processing.2. pulse amplitude modulationPAM is a modulation method using multiple amplitude levels. and QAMquadrature amplitude modulationQAM combines amplitude and phase modulation for data transmission.-n. In one example, 200G × 16 wavelengths has already been shown to be viable, and the combined scaling options are described as adding up to more than 100× bandwidth growth over time.
Microsoft’s planned deployment path starts with CPOco-packaged opticsOptical devices and CPUs are integrated into a single package on the switch side and NPOnear-packaged opticsNPO denotes optical components placed very close to the package. on the accelerator side, then moves to CPOco-packaged opticsOptical devices and CPUs are integrated into a single package on both ends. Other optical interconnect approaches may still emerge, but OCIOptical Compute InterconnectOCI is an optical interface effort aimed at enabling interoperable high-bandwidth links between systems.-MSAMulti-Source AgreementAn MSA defines a common specification that allows multiple vendors to build interoperable components. is currently the most visible candidate for a standardized optical scale-up ecosystem, with first functional Gen 1 implementations and possible interoperability demonstrations expected in 2027.
ASMLAdvanced Semiconductor Materials LithographyASML is the lithography equipment maker named in the report. is not mentioned in this news item.