By Ed Cady
The Fibre Channel interface community has released several new products, including disk drives, chips, adapter cards, backplanes, connectors and cables, that perform at the 2.125 Gbps data rate. Standard Fibre Channel SCA-2, nine-pin D-subminiature and HSSDC-1 connectors still work at the 2.125 Gbps data rate, but cable assemblies now require larger wire gauges and new equalization circuits at shorter distances. Suppliers are marking 2.125 Gbps on their new products to keep them from being confused with the older 1.0625 Gbps data rate.
Among the topics discussed at the December 1999 NCITS T-11.2 Fibre Channel Copper Study Group`s open forum meeting was the 100 W vs. 150 W interconnect issue. Some system orig-inal equipment manufacturers (OEMs) questioned the merits of having 100 W disk drives that would be used with 100 W backplanes.
However, disk drive manufacturers, backed with the current Fibre Channel standard for 150 W drives, have expanded the volume capacity of their recently released 2.125 Gbps Fibre Channel disk drives. These drives are interoper-able with previous 1.0625 Gbps 150 W drives and other devices. Low margins prevent drive suppliers from carrying more than one version of any type of interface unless driven by customer- specific applications and purchase orders; therefore, the 150 W drives remain the Fibre Channel standard.
It appeared that the straw-polled subcommittee meeting still supported 150 W drives. Apparently, most backplanes are still designed for 100 W disk drives. Now that the T-11 committee has had its 10 Gbps project approved, earnest activity of a possible new 10 Gbps disk drive interface may begin. The 100 W vs. 150 W issue may or may not resurface again during this leading-edge development cycle. It is hard to say which connector technology and solution will win approval of the Fibre Channel committee and community. Future Fibre Channel backplane implementation may be based on a potentially new switch backplane specification within the InfiniBand input/output (I/O) interface standard or another interface within the upcoming 10 Gbps Fibre Channel project.
The Fibre Channel T-11.2 subcommittee is currently reviewing 10 Gbps Fibre Channel cable I/O developments and proposals. FCI/Berg has presented its Metral HB 8 differential-pair solution, Molex Inc. has presented its MG I/O connector solution and AMP Incorporated has presented a HSSDC-2 solution. Perhaps, a new connector manufacturer contender will be presenting at the meetings being held this month, February 6-10, 2000.
Hari Technology
Hari interface champions recently provided an updated set of presentations at the December Fibre Channel meeting. Hari technology is said to be able to handle either 2.500, 3.125 or 3.1875 Gbps per channel with four channels combined, creating 10.0, 12.5 12.75 Gbps single links, respectively. The InfiniBand trade association`s specification is 2.5 Gbps; 3.125 Gbps appears slightly favored within the Ethernet`s IEEE 802.3ae committee membership; and 3.1875 Gbps looks like the best solution technical marketingwise within the Fibre Channel market segments. With these varying specifications, different proposals will be reviewed at this month`s Fibre Channel standards meetings.
The meetings will consider many different data rates and supportive eyepattern measurements of various raw cable constructions and optimized differential paired contact/connector constructions. Equalization circuits could be optimized in chip, connector and cable locations.
If four-channel Fibre Channel standardization proceeds, there may be the need for a new eight-position fiber optic connector and cable assembly solution to be initially specified in the final 10 Gbps Fibre Channel specification. More detailed specification work would likely be handled by the small form-factor ad hoc group and formally with the Electronic Industries Alliance (EIA) and International Electrotechnical Commission (IEC) standards groups. Currently, the latest FC-PI document lists SC, SG, MT-RJ and LC fiber optic interface options.
Fiber Optic Connectors
By coincidence, the Telecommunications Industry Association`s (TIA) TR-41.8 committee is said to be considering a vote to set a standard for a small two-position modular fiber optic connector. In addition to the regular group of LC, MT-RJ, SG and OptiJack connectors, there are some newcomers, including Siecor Corp.`s (Hickory, N.C.) SCSG type. This committee originally hoped that the market would decide the primary supplier, and thus, they did not vote for any new connectors at that time.
The opposite appears to be happening, however, as many more connector types proliferate the market with no clear winner in any segment. It would appear that the committee is trying to accelerate market growth and the standardization of one preferred method of connectorizing premise wiring with smaller two-position fiber optic connectors. The next scheduled meeting for the TIA committee is later this month.
InfiniBand Standard
As you are reading this column, the InfiniBand Trade Association may have already announced their choice of backplane connectors within their developing form- factor standard. Will this connector choice represent the best selection for up to 5 Gbps per differentially paired channel with 2.5 GHz bandwidth? It will be interesting to see if the cable I/O connector choice for the one-channel, four-channel and 12-channel link assemblies is the same as or different from their backplane connector family type.
A primary activity of the InfiniBand`s connector standards subcommittee during the first quarter of 2000 is the selection of potentially two, eight and 24 fiber array connectors and cables and viscel transceivers for their evolving standard. This consortium group may piggyback on the smallest-sized two-position connector voting and specification work of the TIA`s committee. The potential Fibre Channel committee selection of an eight-position fiber optic connector or the HIPPI standards selection of a 24-position fiber optic connector may influence the InfiniBand choice, or vice versa.
There appears to be a trend of moving from 150 W Gb to 100 W GB links. Shorter copper differential-paired cable assemblies are still competitive price/performance jumper options vs. optical jumpers. It appears the highest volume jumpers are 0.5, 1.0 and 5.0 m-long copper cable assemblies. But aren`t storage OEMs converging over to fiber optic solutions as primary product offerings anyway?
Conclusion
The new year and century ahead bring a cluster of new connector proposals, selections and specification work for servers and switches. Many engineering departments have had fun opening up their new 12 Gbps BERT testers that they received from their corporate "Santa Claus." Maybe the busiest standards group this year will be the ad hoc small form factor`s high-speed test and methodology subcommittees, for copper and optical cabled connections, and maybe later a possible backplane version.
ED CADY, a Connector Specifier Advisory Board Member, is advanced market engineer, FCI, 15005 N.W. Timmerman Road, Forest Grove, OR 97116; (503) 359-4556; Fax: (503) 359-9273; E-mail: edcady@aol.com.
