By Ed Cady, Contributing Editor
MicroQSFP 28G, micro-miniature Quad Small FormFactor Pluggable 4×28 = 112 Gbps, modules, cages, connectors and cables can be seen at the DesignCon exhibition today and tomorrow in the Santa Clara Convention Center. New product offerings are said to be seen at three or more supplier exhibition booths. TE Connectivity was the initial driver and developer of this new four-lane Link interconnect.
Concurrently the microQSFP MSA consortium of developers has just released its detailed technical specification. Occasionally referred to as µQSFP, it is a very new primary type of high-speed IO interface system used to connect much higher density, higher port count, server, storage, switch, video and communication systems. The industry SFF committee is now engaged in developing some new detailed specifications. Expect to see this new microQSFP being added into Ethernet IEEE-803bj and InfiniBand EDR specifications standards. FibreChannel 4x28Gbps inter-switch applications will use this as well. Different consortium plugfests will be certifying compliance and interoperability standards.
In two past lives we developed and produced external SFP and SFP+ four-lane passive copper cables for some high-volume custom one-to-one and one-to-four hydra configuration applications. So those were 4×5=20 Gbps and 4×10=40 Gbps Link network connections mostly using small gage size twin-axial cable for ToR rack to leaf server and other architectures. A few OEMs have been looking at using regular SFP28G with one four-lane leg going to the same SFP28G connector for their custom applications. But now they will likely use the microQSFP28G instead. It will be interesting to see the total cost of using microQSFP28G versus QSFP28G standard or four-lane SFP28 custom.
MicroQSFP modules will need good marking for visual orientation and differentiation from existing SFP modules and cables. It would seem that the new Cages have vent hole sizes configured to prevent the very high frequency short wave lengths from escaping but still allow some hot air flow. The connectors include a higher density contact pitch, right-angle internal edge board, PCB mount type. There may be a back-to-back, edge, hybrid PCB connector for a separable or non-separable internal connection to cable or PCBA reach for inside-the-box, intra-board extenders. Some contacts would still be right angle for power and system management circuits.
At 25-28 Gbps per lane data rate more cable types will be active copper and active optical versus the very short reach limited passive copper cable types. Active copper cables will have EPROM embedded chips that can provide smart link functions like cable type, manufacturer identification, security and inter-compatibility handshaking. Another plug PCB embedded chip can be used for signal conditioning, retiming or re-driving. Active Optical Cable (AOC) applications will soon include CameraLink HS standard interface for new video machine vision and surveillance networks. New micro-QSFP AOCs will be used in high volume ToR to EoR datacenter inter-rack, point-to-point links as well as wireless base-station infrastructure connections.
Interesting that the micro-QSFP 4×28 G connector is as dimensionally wide as the new four-lane QCuLink PCIe 4×16 G connector but higher and longer. It seems that you could use a smaller, fewer pinned version of the microQSFP interconnect and create a new one-lane version of a microSFP28G. Then you could have one microQSFP to four legs of microSFP hydra cables. Another adapter cable possibility might be having one microQSFP connector and a four-lane single leg, implementation of the USB3.1 TYPE C single or dual connector on the other end. Or one microQSFP with 2-4 legs of TYPE C. There will be some microQSFP28G to standard size QSFP28G cables and three microQSFP28 legs connecting to one CXP connector.
microQSFP56 is a developing 50-56 Gbps next-generation version. It appears that this would be used for mostly active optical modules, active optical cables and maybe some very short active copper cables applications which may be more expensive and power consuming. A nascent 4×50 Gbps =200 Gbps Ethernet standard may manifest later this year.
Some new SFF committee specifications will become available, so keep your eye on www.sffcommittee.org. Go to the SFF-8024 naming spec for complete listing of applicable SFF specifications. Read the microQSFP MSA consortium’s recent announcement here. The members of the SFF committee do detailed interconnect specifications for open industry standard groups as well as the originating QSFP MSA private consortium. Expect to see microQSFP connecting new Ethernet switches and blades within active equipment at this year’s INTEROP show. The major threat to continued high volume QSFP related interconnect usage is the advent of inside-the-box, mid-board optical engines and external passive optical cables like the new MXC interconnect.