MSAs vie for 10Gbit/s

For an optical transceiver — which provides both the transmit and receive optoelectronic functions — multi-source agreements (MSAs) have arisen that enable module suppliers to provide system OEMs with reliable second sources and promote adoption of technology.

The aim is to independently develop and supply standard compact, hot-pluggable 2.5Gbit/s (OC-48) transceiver modules of open design that define common electrical interfaces, physical characteristics, signalling schemes and other characteristics (a uniform package form factor, size, connector type and electrical pin-outs). This ensures interoperation between different vendors' transceiver module holders, modules and customer PCBs and a choice of compatible second sources.

Pluggability eliminates fibre pigtails and pin through-hole devices. These are difficult to assemble in high-volume systems, since they do not require soldering to the board or a board cut-out. The modules are suitable for both hot-pluggability in the field when mounted at the faceplate of the equipment and for cold-plugging "in-board" when field access is not required.

The transceiver can be installed in live systems by plugging in when and where needed. This increases flexibility by allowing response to changing traffic patterns and eliminates downtime during upgrades and service calls.

Flexible services are also enabled by multi-rate features (from 155Mbit/s to 2.7Gbit/s).

However, while transceivers have been operating at 2.5Gbit/s for several years, the market is now migrating to 10Gbit/s.

The 10Gbit/s transceiver module has been developed for campus trunking, data aggregation and switching, enterprise-to-metro uplinks, data trunking in metro networks, equipment room point-to-point links and test systems for the 10 Gigabit Ethernet (10GbE) and Fibre Channel markets.

The first MSA, for the 70-pin XENPAK, was launched in March 2001 by Agere and Agilent (after they abandoned the XGP initiative to create a GBIC-sized module). XENPAK supports all four transceiver types of the IEEE802.3ae 10GbE standard (10GBASE-LR for 10km long reach over single-mode fibre): 850nm serial, 1310nm serial, 1310nm WWDM, and 1550nm serial. XENPAK was joined in May 2001 by Mitsubishi Electric, Pine Photonics, Optillion and Tyco Electronics. Members now include Blaze Network Products, ExceLight, E2O Communications, Finisar, Hitachi Cable, Ignis Optics, Infineon Technologies, JDS Uniphase, Intel, Luminent, Molex, Multiplex, NEC, Network Elements, Nortel, OpNext, Picolight, Stratos Lightwave and Vitesse Semiconductor.

Devices are 4.8"x1.5"x0.7", have an electrical input/output based on the XAUI 10Gbit/s Attachment Unit Interface (4-channel x 3.125Gbit/s), are front-panel pluggable and use an SC duplex connector. XENPAK was one of the first modules to plug into the board's side, rather than top, without taking cards out of the chassis.

At ECOC 2001 Agilent was first to demonstrate a 1310nm XENPAK transceiver, the HFCT-701XB. At March's OFC 2002 it demonstrated interoperability with the XAUI SerDes ICs of PMC-Sierra, Marvell Technology and Texas Instruments. Meanwhile, Agere's 1310nm AE20MRCAA is due for production in Q4/2002.

This July Optillion's TOP 3010-SC (its first product, launched at November 2001's Lightspeed Europe) and Mitsubishi Electric's MF-11KCXB-001WA became the first XENPAK transceivers to interoperate. They also doubled reach to 20km.

In June Optillion also sampled its 1550nm TOP 5010 for the 10GBASE-ER extended-reach (40km) standard. In Q4/2002 Mitsubishi also started shipping 10GBASE-ER transceivers. "The 10G 1550nm Serial XENPAK transceiver will extend 10G Ethernet technology [from LANs] to the metro network," adds Pine Photonics president and CEO Dr Hsing Kung. Increased reach extends applications from aggregated uplinks to high-volume, server-to-switch and storage-to-switch links.

For shorter reach (10GBASE-LX4) Molex's MuxLink module began sampling in April. However, XENPAK was designed for dissipating the heat from power-intensive lasers for long-reach, so the module is large. A transport slot needs to be cut into the board to accommodate it, whereas most applications are data-centre or campus interconnects.

"What's needed is a higher-density, single-sided application," says Michael Peppler, Agere's senior strategic marketing manager. "[XENPAK-based transceivers] may get into the first generations of 10Gbit/s equipment, and then it will trend toward the other small-form-factor transceivers," he says.

March's OFC 2002 saw the launch of XPAK (www.xpak.org), which uses the XAUI interface and 70-pin connector but with new thermal and EMI mitigation features and mechanical outlines. It is the first MSA to yield sample front-panel pluggable modules with PCI-compliant height, width and bezel opening (mounted on the PCB, rather than in a cut-out), including 10GbE network interface cards. For dense line-cards a low-profile version (2"x1.5"x0.5", slightly larger than a GBIC module) accommodates 20 modules stacked above and below a 17" board (see Fig 2) compared to eight XENPAK modules.

September's Revision 2.0 of the spec added a tall-profile thermally enhanced version for 8-across switch environments plus a mid-board mounting system for telecoms.

XPAK members comprise:

• participants, building modules (co-founders Intel, Infineon Technologies and Picolight plus Molex and Tyco Electronics);
• sponsors, using modules (McData and QLogic);
• contributors, supporting MSA development (Broadcom, Forte Development, OEPIC and Quake Technologies).

In September membership grew to 21 firms, with participants Blaze Network Products, E2O, Fujitsu Quantum Devices, Kodeos Communications, Network Elements, Optium, Pine Photonics and Red Clover Networks, plus sponsors JNI and Spirent.

Short-wave (850nm) implementations support up to 300m and long-wave (1310nm) up to 10km (80% of 10GbE port applications). XPAK will eventually support 40km reach.

September saw the launch of Intel's TXN17201/9, the first 10Gbit/s small-form-factor transceiver for short-reach data-centre links (up to 65m) over multi-mode fibre.

Late July saw XENPAK founders Agere and Agilent form the X2 MSA (www.x2msa.org), which targets lower-end switches and enterprise applications and is supported by JDS Uniphase, Mitsubishi Electric, NEC, Optillion, Opnext and Tyco Electronics.

X2 maintains XENPAK's electrical I/O specification and 70-pin connector, supporting four-wire XAUI or OIF SFI4_P2 interfaces and serial electrical interfaces. It also has similarly robust thermal performance and electromagnetic shielding. However, it consumes less power and is 40% shorter.

Multiple heat sink and front bezel options allow for above-board mounting in "front panel" and "mid-board" configurations, or in a conventional PCI card. It can also be adapted to cover a wider range of applications, including 802.3ae 10 Gigabit Ethernet, ANSI/ITUT OC192/STM-64 SONET/SDH interfaces, ITUT G.709, OIF OC192 VSR, and INCITS/ANSI 10 Gigabit Fibre Channel. X2's flexibility is expected to drive higher-volume manufacturing and lower-cost optics.

X2 is initially focused on 1310nm links over single-mode fibre up to 10km and "second generation" 10Gbit/s enterprise, storage and telecom applications such as Ethernet, Fibre Channel and telecom switches and standard PCI-based server and storage connections. X2 transceivers should start shipping in first-half 2003.

March's OFC 2002 also saw the launch of the 10 Gigabit Small Form-factor Pluggable (XFP) module MSA (www.xfpmsa.org) by a 10-member group of Broadcom, Brocade Communications Systems, Emulex, Finisar, JDS Uniphase, Maxim Integrated Products, ONI Systems (now part of Ciena), Sumitomo Electric's ICS, Tyco Electronics and Velio. The MSA is now supported by 44 vendors, including 33 added in May plus Stratos Lightwave in July. Some of these companies are also working on XPAK.

July's first-draft spec defined mechanical, thermal and EMI features as well as the new XFI differential serial electrical interface for direct connection to on-board electronics, similarly to 1 and 2.5Gbit/s SFF and SFP (small form-factor pluggable) modules.

Much of the electronics, including the physical-layer chip (Ethernet MAC or SONET framer), are on the line-card (rather than inside the module, like XENPAK and XPAK). Rather than a four-lane electrical interface, XFP uses a single 10Gbit/s electrical interface. This cuts power consumption and size to as little as the SFP connector. XFP claims the highest port density and the smallest form factor (2.3"x0.33"x0.7"), enabling 16 ports on a 22" line card.

Also, support for 9.95–10.7Gbit/s data rates makes it protocol-independent, enabling greater economies of scale.

In September Luminent Inc claimed the first demonstration of an XFP module. However, XFP modules should be available in volumes 6–12 months after XPAK modules.

X2 and XPAK are very similar thermally and mechanically, with just a few mm difference in size in any direction, and perform nearly identically. A goal of some XPAK and X2 members is therefore to merge the two into a single, four-lane GBIC-sized solution.

At the front bezel X2 uses a single-stage EMI seal from bezel to module, requiring the bezel to be conductive and unpainted and the gasket to be compliant over multiple mate cycles. XPAK uses a two-stage seal, where a compliant gasket relieves tolerance requirements between PCB and bezel (only a few mate cycles) with a relatively non-compliant gasket between module and module holder.

At the rear electrical connector X2 uses a separate cage inserted into the module holder. XPAK uses a shield (built into the single-piece module holder) tightly connected to the electrical ground on the customer PCB.

Agilent says that it is "not commenting further regarding the prospects of a X2 MSA and XPAK MSA merger". However, Optillion's CEO Patrik Evaldson says it is "very likely" that XPAK and X2 will merge. "The technical solutions are trying to achieve the same thing," he says. "There are no sticking points."

10Gbit/s tranceiver market to rise from USD68.7m in 2001 to USD3.26bn in 2006
The 10Gbit/s datacom transceiver market will rise from USD68.7m in 2001 to USD3.26bn in 2006, says ElectroniCast (www.electronicast.com).

"The high-speed datacom transceiver market was launched in 1998 with the success of full-speed Fibre Channel, Gigabit Ethernet, and VCSEL transceivers, whose markets tripled in 1999," said president Stephen Montgomery.

"The datacom and telecom markets have converged on approximately the same data rate for the first time. As a result, there will be technology and product sharing across these two market segments," he says. "Initially, the 10Gbit/s technology and transceiver modules that have already been developed for telecom will find use in datacom applications. However, datacom will always be asking for low-cost connectorised transceiver modules," he adds.

Six types of transceiver will compete. Three types of 850nm transceiver will consume about half the unit volume during 2001–2011. This is less than the 85% dominance of multimode solutions at 1Gbit/s, due to the growth of 1310nm single-mode serial transceivers as well as 1310nm WWDM and 1550nm.