OIF has published the eagerly awaited Implementation Agreement (IA) for the 400ZR coherent optical interface. Optical transceivers designed in accordance with the 400ZR IA are expected to have a significant impact on data center interconnect (DCI) and metro access applications.
The group began work on the 400ZR IA in 2016 at the behest of data center operators looking for an interoperable, cost-effective approach to the support of DCI links at greater than 100 Gbps (see “OIF launches coherent transmission projects”). Communications service providers became interested in such an approach as well, which led to OIF members expanding their work to accommodate both user requirements. The resulting IA covers a pair of application scenarios:
- amplified, point-to-point DWDM links with reaches of 120 km or less
- unamplified, single-wavelength links with a loss budget of 11 dB.
The 400-Gbps implementations described in 400ZR are based on single-carrier coherent DP-16QAM modulation using low-power DSPs. The DSPs support absolute (non-differential) phase encoding/decoding and leverage a concatenated FEC (C-FEC) with a post-FEC error floor of <1.0E-15. A 400ZR operates as a 400GBASE-R PHY.
“As a member-driven organization, OIF’s work toward the 400ZR IA was the combination of significant interest from network operator members and component supplier members responding to that demand,” explained Karl Gass, OIF Physical and Link Layer (PLL) Working Group – Optical vice chair. “The 400ZR IA is the culmination of this significant effort by OIF member-companies and is critical for managing cost and driving interoperability for the industry.”
“400ZR is a key enabler of Microsoft’s regional architecture for the 400G generation,” said Mark Filer, principal optical engineer in Microsoft Azure. “The creation of a multi-vendor, interoperable coherent interface to meet these needs would not have been possible without the extensive work and cooperation of OIF members and leadership.”
The IA is form-factor agnostic, although it is anticipated that the significant majority of implementations will leverage such pluggable form factors as QSFP-DD, OSFP, CFP2, and CFP8. It is also applicable to onboard optics, including applications targeted by the Coalition for On-Board Optics (COBO). While the 400ZR IA has only just been published, vendors have already gotten a jump on demand by announcing 400ZR products (see, for example, "NeoPhotonics sampling 400ZR ClearLight OSFP coherent optical transceivers for data center interconnect," "Inphi sampling COLORZ II QSFP-DD optical transceiver for 400ZR data center interconnect," and "Acacia offers range of 400-Gbps coherent optical modules")
The document that describes the 400ZR IA is available to download from the OIF’s website.
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