OIF publishes CEI 4.0 for CEI-56G 56-Gbps applications

The OIF has released "Common Electrical (I/O) CEI 4.0," which creates SerDes specifications 56-Gbps I/O applications. Commonly referred to as CEI-56G, the specification sets add PAM4 and Ensemble NRZ (ENRZ) as modulation schemes alongside NRZ. The publication follows two years of demonstrations at OFC and represents the OIF's eighth generation of electrical interface specifications, rolled out over 18 years.

The OIF has released "Common Electrical (I/O) CEI 4.0," which creates SerDes specifications 56-Gbps I/O applications. Commonly referred to as CEI-56G, the specification sets add PAM4 and Ensemble NRZ (ENRZ) as modulation schemes alongside NRZ. The publication follows two years of demonstrations at OFC and represents the OIF's eighth generation of electrical interface specifications, rolled out over 18 years.

OIF members focused on minimizing power consumption while balancing link budget and latency. The specification sets include:

  • CEI-56G-USR-NRZ: Ultra short reach, die-to-die inside multi-chip-modules, NRZ modulation
  • CEI-56G-XSR-NRZ: Extra short reach, chip-to-driver, NRZ modulation
  • CEI-56G-VSR-PAM4: Very short reach, chip-to-module, PAM4 modulation
  • CEI-56G-MR-PAM4: Medium reach, chip-to-chip, one connector, PAM4 modulation
  • CEI-56G-LR-PAM4: Long reach, chip-to-chip, two connectors over backplane, PAM4 modulation
  • CEI-56G-LR-ENRZ: Long reach, chip-to-chip, two connectors over backplane, ENRZ modulation.

The OIF says it plans future clauses in an upcoming CEI 4.1 release.

"The industry continues to face challenges for diverging requirements regarding link latency and concerns with power consumption at the higher data rates," saidKlaus-Holger Otto of Nokia, OIF Technical Committee Chair. "Documenting channel definitions in more granular reaches and multiple modulation schemes allows for the optimization of silicon chip designs, channel architectures, and network operator use cases. These parameters for 56 Gbps will be used as building blocks for protocol specifications written by other organizationsacross the industryso the forum wanted toprovide definitions that met their unique needs."

The OIF has been working in the 56-Gbps arena since at least 2012 (see, for example, "OIF launches 56-Gbps electrical interface projects") It has leveraged this work, particularly CEI-56G-VSR, to investigate specifications at even higher transmission rates (see "OIF CEI-112G Project tackles 100-Gbps serial electrical links").

CEI 4.0 can be found on the OIF website.

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