BY ED CADY
It seems like just a short while ago when the networking industry transitioned from using 10/100-Mbit/sec ports to primarily 1.0625-Gbit/sec (Gigabit Ethernet) ports. The widespread rollout of Gigabit Ethernet has caused the advent of many forms of 10-Gbit/sec Ethernet for switch backbone links. Most switch uplinks consists of two or more 10-Gbit/sec ports. Higher-end switches have dozens of 10-Gbit/sec ports as well as some trunk multi-port backbone links.
Today in the interconnect industry, there is a rush to win 10-Gbit/sec single end-user, horizontal-building, and data-center design-ins. This column will take a look at some of the current activities with copper and optical standards, products, applications, and interconnect components.
IEEE 802.3an, also known as 10GBase-T, is a newly released Ethernet copper specification for the four-lane x 2.5-Gbit/sec per pair electrical signaling intended for twisted-pair cable assemblies with Category 6A or better rating. Purposely, there is no connector or cable assembly specification within this new standard. Current Category 6 unshielded twisted-pair (UTP) interconnect products seem to work only for 37-meter link lengths, not the usual 100 meters for horizontal wiring.
Alien crosstalk and other factors make foil-shielded Category 6A and dual-shielded cables like Category 7 a lower-risk design-in choice. The Category 7 IEC connector is not RJ-45, but is based on The Siemon Co.’s TERA connector and cabling system. Some suppliers are still working to improve the RJ-45 performance range.
IEEE 802.3ak, also known as 10GBase-CX4, uses the SFF-8470 copper connector for its 4-lanes x 3.125-Gbit/sec per pair, for a total of 12.5 Gbits/sec. This standard does have a connector and cable assembly specification section.
Various stacked 4x multi-receptacle connectors are providing increased density across “pizza boxes” and blades. The XAUI-2-based chips with 6 Gbits/sec per differential pair upgrade products have been popular, and still work to 15+ meters. Tiny, active low-cost equalizer chips embedded in cables or receptacles, or feed-through connectors, allow performance to 50+ meters for CX4 current applications. A cable assembly with one 12x connector fanout to six Category 6A receptacles or plugs is a new six-port density solution.
CX4 cable assembly products vary in performance. Some new-generation CX4 interconnect engineering prototypes have been demonstrated to 17 and 25 Gbits/sec per pair, while the majority of design-in is in the 4, 5, 6, or 8.5-Gbit/sec range. There is also a quickly growing 10- and 12.8-Gbit/sec design-in range because of the requirement to have multi-generational capability and many custom backbone I/O product design-ins.
Some 100-Gbit/sec Ethernet CX early developers are looking at using a 12x InfiniBand connector with 12 lanes running at 10 Gbits/sec per pair in a serial aggregation architecture. Some may want a smaller connector supporting the 24 different pairs, yet other OEMs may consider staying with the 4x connector by supporting four lanes x 25-Gbits/sec per pair for 100 Gbits/sec.
IEEE 802.3ap, also known as 10-Gbit Backplane Ethernet, is a new specification for running either four lanes x 3.125 Gbits/sec and/or one lane x 10.5 Gbits/sec. This specification covers signaling running from chips, through boards and multiple connectors, but does not specify what connectors or boards to use. High-speed cabled backplane expander assemblies are longer solutions compared to current FR-4 printed circuit boards.
CompactPCI and VME specifications support various Ethernet signaling running through the hard metric 2-mm connectors (frequently referred to as 2 mm HM). New 2-mm cabling fanout systems with Category 6A or Category 7 connectors and raw cables are a popular upgrade product for a large installed base within the military/aerospace and telephony market segments.
A collaboration
IEEE 802.3’s liaison work group and the INICTS-T11 Fibre Channel physical layer committee are working to complete a jointly supported one-lane SFP+ interconnect specification for 10.5 Gbits/sec and 8.5 Gbits/sec one-lane links. Besides the market offering of several SFP+ optical transceivers for very long links, another popular solution will be SFP+ copper to same or in fanout (sometimes called “octopus”) configurations using a 12x InfiniBand-style connector as a multiport single connector. A portion of the storage area network and data-communications switch markets likely will use SFP+ versus dedicated optical with LC cables and copper enhanced HSSDC-2 connector and cabling systems used in IEEE-802.3z Gigabit Ethernet.
Ethernet observers are also looking closely at the development of a new multi-source agreement (MSA) consortium that is also working with the InfiniBand consortium. The Quad SmallFormfactor Pluggable (QSFP) proposed from www.qsfpmsa.org is a four-lane optical multimode transceiver using a wider version of the current SFP shield cage and PCB edge connector. A copper-plugged QSFP cable assembly could be competing with CX4 in the data-center environment, as could the 8-fibered MTP/MPO assemblies.
TIA-568 cabling standards have been upgraded to cover Category 6A applications and installations for building wired infrastructures. Wiring cabinet proprietary block products are declining in design-ins and TAM (total available market) versus RJ-45 interconnects.
Looking ahead
The chip technology and supporting interconnect that offers the lowest power consumption and cooling requirements, and higher-density footprint, likely will be holding major TAM design-in percentage. Ethernet, InfiniBand, and Fibre Channel cross-compatibility are key for winning chip and interconnect product design-ins.
Some Ethernet 10GBase-T evangelists would like to see a higher-density and higher-speed copper connector versus the current Category 6A and Category 7 connectors. There seems to be a need for the Category 7 connector to have the enhanced IEEE 802.3ah Power over Ethernet (PoE) capabilities that are available with Category 6 RJ-45 receptacles. Will there be a future IEC Category 8 copper cabling specification?
Multiple 1-Gbit Ethernet signals have been proven to work within the new MiniRJ-21 connector that is replacing the very old delta-ribbon style 50-position RJ-21 connector. Can the MiniRJ-21 handle 802.3an 2.5-Gbit/sec signals as well as CX-4 3.125-Gbit/sec signals, or will a new connector become either an industry or a de facto standard?
Will there be a need for environmentally hardened SFP or Category 7 plugs and cables, as there has been for Gigabit Ethernet within overmolding and circular metal shells using RJ-45 Category 5e connectors?
10-Gbits/sec has been a multi-technology and standard-interfaces roadmap crossover point. How will the Ethernet community compete with developing 4 lanes x 10 for 40 Gbit/sec ATM, and 160 Gbit/sec SONET standards and products?
Heat, power, and density factors within chips and modules will continue to drive the design for smaller, high-performance connectors and provide major TAM to the standard that has the best price/density solution set. CX4 chips have had a best overall heat/power/size story, so CX4 forecasting remains healthy for the data center for now.
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ED CADY contributes this standards update column as a member of Connector Specifier’s editorial advisory board. He is also strategic market director at Meritec (www.meritec.com).
