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OSFP Rev 5.1 is the latest 8-lane pluggable transceiver specification released by OSFP MSA. It unifies design requirements for 400G, 800G and 1.6T (OSFP1600) implementations, covering mechanical, electrical, thermal, optical and CMIS-compliant management interfaces.

Mechanical Specifications

OSFP transceivers are categorized into Type 1/2/3 with differing maximum front-end widths. While the main body width stays consistent with Rev4.1, optional label mounting solutions including in-cage placement are newly added. A dedicated chapter for OSFP1600 is introduced: the front edge of signal pads on its gold-finger edge connector is positioned closer to the module stop shoulder; the PCB neck cutout can be eliminated, and tighter tolerances are specified for latch pocket depth and angle to minimize longitudinal module backlash. An OSFP1600 module can be inserted into legacy OSFP/OSFP800 ports at the cost of degraded mechanical reliability, whereas legacy modules achieve full backward compatibility into OSFP1600 cages.

Cage and Connector

Single-row SMT cages inherit the prior design baseline. A new stacked SMT cage with 19.9 mm vertical pitch (upgraded from the original 14.9 mm) is defined to accommodate bottom-port ride-on heatsinks and enable higher-power operation. Tighter positional tolerances are enforced on stacked SMT connector contact areas to fit OSFP1600 form factor. For OSFP1600 1×1 cages, gold-plated pad landings (solder-free) replace conventional PCB pads as the connector seating plane, with reduced dimensional allowance between cage latch springs and module stop shoulders. Press-fit stacked cage specifications remain unchanged.

Cable Connectors

New CHF-A, CHF-B and back-to-back (B2B) layouts in 1×1 and 2×1 configurations are added to support host-side cable-attached interconnect.
Insertion Force & Durability
Nominal insertion force remains 40 N, rising to 55 N for variants with ride-on heatsinks; minimum retention force is specified at 125 N. Endurance criteria stay unchanged: 50 mating cycles for modules and 100 cycles for connectors and host cages.

Thermal Performance

Case temperature grading (including commercial grade 0~70 °C) and connector thermal specifications carry over from earlier revisions. Appendix G is newly included to standardize thermal monitoring for high-power modules: instead of relying solely on case temperature, the module shall compute a single monotonic temperature reading based on margin data from multiple internal sensors (laser, DSP, TIA) and report this consolidated value to the host system.

OSFP-RHS (Ride-on Heatsink) Modules

Standing at 9.5 mm in height, RHS modules omit integrated on-board heatsinks and fully depend on cage-mounted ride-on heatsinks for cooling. The new OSFP1600-RHS variant follows OSFP1600 dimensional tolerances for gold fingers and latch structures. Stacked RHS cages adopt the updated 19.9 mm pitch with differentiated heatsink cutout dimensions between top and bottom port positions.

Optical PMD Block Diagrams

New 1600G PMD options are supplemented, including DR8, coherent optics, 4×400G coherent, DR4.2, 2×FR4, FR4, FR8/LR8 and SR16/SWDM4. Definition of receptacle channel assignments is expanded for MMC, dual MMC, SN-MT and dual SN-MT. Interoperable channel mapping is confirmed among MPO, AirMT and 3M EBO fiber connectors.

Electrical Interface

The 60-pin footprint is retained with 8 differential TX pairs and 8 differential RX pairs. A new 1.6TAUI-8 electrical lane standard is added: 224 Gbaud PAM4 signaling supporting 8×200 Gb/s lanes for an aggregate 1.6 Tb/s throughput, alongside legacy electrical interfaces: 800GAUI-8 (112G PAM4), 400GAUI-8 (56G PAM4) and dual CAUI-4 (25G NRZ). The pinout table is extended to support multiple lane configurations: 1×1.6T, 2×800G, 4×400G and 8×200G. The low-speed interrupt signal is uniformly defined as non-inverted H_INT for INT/RSTn. Four VCC power pins remain in place with 10 A total rated current and a maximum 33 W power budget (effective since Rev4.0), while Power Class 1~8 classification is unchanged.

Miscellaneous Updates

Existing ESD compliance requirements are preserved. Three new appendices are issued: Appendix D for latch-release width test fixture specification, Appendix E for cage spring position inspection gauge, and Appendix F explicitly documenting mechanical incompatibility between OSFP and OSFP-XD form factors.

Conclusion

While maintaining full backward compatibility with legacy OSFP generations, OSFP Rev5.1 incorporates OSFP1600 (1.6T) support, enhanced 19.9 mm-pitch stacked thermal design, tightened mechanical tolerances, standardized high-power thermal monitoring and extended optical receptacle options, making it the most comprehensive OSFP specification available to date.