The Small Form Factor Pluggable Double Density (SFP-DD) Multi-Source Agreement (MSA) Group released an updated (v4.1) hardware specification for 100+ Gbps, high-density networking equipment. The SFP-DD form factor uses 2-lane pluggable modules, is backward compatible with SFP+ and offers improved host to module management communication based on a Two-Wire-Interface (TWI).
SFP-DD revision 4.1 hardware specification includes added features to support ResetL, dual function IntL/TXFaultDD and ePPS. Newly added timing tables will also allow for low speeds signals, soft control and module status. The former chapter 7 Management Interface is now part of chapter 4, Electrical Specification. The updated hardware specification includes port mapping, optical connectors and module color coding moved out of Mechanical and Board Definition chapter 5 and into a new chapter 5. Lastly, TS-1000 Normative Module and Connector performance requirements were added as Appendix A.

SFP-DD MSA promoters include Alibaba, Broadcom, Cisco, Dell EMC, HPE, Huawei, II-VI Incorporated, Intel, Juniper Networks, Lumentum, Molex, Nvidia and TE Connectivity. Contributors include Accelink, Amphenol, AOI, Eoptolink, FIT, Fourte, Genesis, Hisense, Infinera, Innolight, Maxim Integrated, Multilane, Nokia, Oclaro, Senko, Source Photonics, US Conec and ZTE.
http://sfp-dd.com/2020/08/sfp-dd-msa-releases-updated-4-1-hardware-specification/