Gazettabyte

Part 1: Client-side transceivers

First CFP2 single-mode and multi-mode transceiver announcements
Cisco Systems unveils its CPAK module
100 Gigabit QSFPs from Kotura and Luxtera
CFP2 and 40km CFP 10x10 MSA modules
Infiniband FDR and 'LR4 superset' QSFPs

The recent OFC/NFOEC exhibition and conference held in Anaheim, California, saw a slew of optical transceiver announcements. The first CFP2 client-side products for single-mode and multi-mode fibre were unveiled by several companies, as was Cisco Systems' in-house CPAK transceiver.

The CFP2 is the pluggable form factor that follows the first generation CFP. The CFP MSA announced the completion of the CFP2 specification at the show, while several vendors including Avago Technologies, Finisar, Fujitsu Optical Components, NeoPhotonics, Oclaro and Oplink Communications detailed their first CFP2 products.

The 40 and 100 Gigabit CFP2 is half the size of the CFP, enabling at least a doubling of the CFP2 transceivers on a faceplate compared to four CFPs (see table below). The CFP2 is also future-proofed to support 200 and 400Gbps (See first comment at bottom of CFP2 story).

Another difference between the CFP and the CFP2 is that the CFP2 uses a 4x25Gbps electrical interface. Accordingly, the CFP2 does not need the 'gearbox' IC that translates between ten, 10 Gigabit-per-second (Gbps) lanes to four, 25Gbps electrical lanes that interface to the 4x25/28Gbps optics. Removing the gearbox IC saves space and reduces the power consumption by several watts.

The industry has long settled on the SFP+ at 10Gbps while the QSFP has become the 40Gbps form factor of choice. With 100Gbps still in its infancy, transceiver vendors are pursuing several client-side interfaces. Much work will be needed to reduce the size, power consumption and cost of 100Gbps interfaces before the industry settles on a single pluggable form factor for the single-mode and multi-mode standards.

CFP2 announcements

Finisar demonstrated two CFP2 modules, one implementing the IEEE 100GBASE-LR4 10km standard and the other, the IEEE 100GBASE-SR10 100m multi-mode standard. The company is using directly-modulated, distributed feedback (DFB) lasers for its CFP2 LR4. In contrast, the CFP module uses more expensive, electro-absorption modulator lasers (EMLs). Finisar demonstrated interoperability between the two LR4 modules, an EML-based CFP and a DFB-based CFP2, at the show.

* An ER4 CFP2 is under development
** Oclaro disclosed indium phosphide components for a future CFP2 line side pluggable

Using directly modulated lasers also reduces the power consumption, says Finisar. Overall, the CFP2 LR4 consumes 7W compared to a 24W first-generation CFP-based LR4.

"We can migrate these [directly modulated laser] designs to a single quad 28 Gig photonic integrated circuit TOSA," says Rafik Ward, Finisar's vice president of marketing. "Likewise on the receive [path], there will be a quad 28 Gig ROSA." The TOSA refers to a transmitter optical sub-assembly while the ROSA is the receiver equivalent. Ward says the CFP2s will be in production this year.

Several module and chip makers took part in the Optical Internetworking Forum's (OIF) multi-vendor demonstration of its 4x25 Gigabit chip-to-module electrical interface, the CEI-28G-VSR. The demonstration included CFP2 LR4s from Finisar and from Oclaro as well as Luxtera's 100Gbps shorter reach module in a QSFP28. Oclaro's CFP2 is expected to be in production in the third quarter of 2013.

Another standard implemented in the CFP2 is the 100GBASE-SR10 multi-mode standard. Avago Technologies and Finisar both detailed CFP2 SR10 modules. The SR10 uses 10 VCSELs, each operating at 10Gbps. The SR10 can be used as a 100Gbps interface or as 10 independent 10Gbps channels.

The CFP2 SR10 can be interfaced to 10 Gigabit Ethernet (GbE) SFP+ modules or combinations of 10GbE SFP+ and 40GbE QSFPs. "What people are looking for using the CFP2 multi-mode module is not only for the 100 Gig Ethernet application but interoperability with 40 Gig Ethernet as well as 10 Gig Ethernet modules," says I Hsing Tan, Ethernet segment marketing manager in the fibre optics product division at Avago.

The SR10 electrical interface specification supports retiming and non-retiming options. The Avago CFP2 module includes clock data recovery ICs that can be used for retiming if needed or bypassed. The result is that Avago's CFP2 SR10 consumes 4-6W, depending on whether the clock data recovery chips are bypassed or used.

Meanwhile, NeoPhotonics became the first company to announce the 10x10 MSA in a CFP2.

NeoPhotonics has not detailed the power consumption but says the 10x10Gbps CFP2 is lower than the CFP since all of the chips - photonic and electrical - are a newer generation and much work has gone into reducing the power consumption.

"Demand is quite strong for the 10x10 solution," says Ferris Lipscomb, vice president of marketing at NeoPhotonics. "The CFP2 version is being developed, and we expect strong demand there as well."

The key advantage of the 10x10-based solution over a 4x25Gbps design is cost, according to NeoPhotonics. "10x10 enjoys the volume and maturity of 10 Gig, and thus the cost advantage," says Lipscomb. "We believe the 10x10 CFP2 will follow the trend of the 10x10 MSA CFP and will offer a significant cost advantage over CFP2 LR4-based solutions."

Cisco's CPAK

Cisco finally showed its in-house silicon photonics-based CPAK transceiver at OFC/NFOEC. The CPAK is the first product to be announced following Cisco's acquisition of silicon photonics player, LightWire.

Cisco says the CPAK is more compact than the CFP2 transceiver with the company claiming that 12 or more transceivers will fit on a faceplate. "While the industry is leapfrogging the CFP with the CFP2, our CPAK leapfrogs the CFP2 because it is much more efficient from a size and power consumption perspective," says Sultan Dawood, a marketing manager at Cisco.

Vendors backing the CFP2 stress that the CPAK is only slighter smaller than the MSA module. "The CFP2 and the CPAK are both interim form factors pending when the CFP4 becomes available." says Avago's Tan. "Any product [like the CFP2] governed by an MSA is going to see strong market adoption."

Cisco's CPAK transceiver Source: Cisco

The CFP4 specification is still being worked on but 16 CFP4s will fit on a faceplate and the transceiver is scheduled for the second half of 2014.

At OFC, Cisco demonstrated the CPAK implementing the 100GBASE-LR4 and -SR10 standards. The CPAK transceiver will be generally available in the summer of 2013, says Cisco.

CFP

Oplink Communication and hybrid integration specialist, Kaiam, showed a 100Gbps 10x10 MSA CFP implementing a 40km extended reach.

The 10x10 40km CFP is for connecting data centres and for broadband backhaul applications. The CFP electro-absorption modulator lasers coupled to a wavelength multiplexer make up the TOSA while the ROSA comprises avalanche photodiode receivers and a demultiplexer. Samples will be available in the second quarter of 2013, with production starting in the third quarter.

Source Photonics announced a second-generation 100GBASE-LR4 CFP with a power consumption of 12-14W.

Meanwhile, Effdon Networks detailed its first 100Gbps product, a CFP with a reach of 80km. Until now 100Gbps CFPs have been limited largely to 10km LR4 while the first 100Gbps CFPs with a reach of 80km or greater being 4x25Gbps direct-detection designs that can include specialist ICs.

100 Gig QSFP

Luxtera and Kotura, both detailed 100 Gigabit QSFPs that use their respective silicon photonics technology. The Kotura design uses two chips, has a reach of 2km and is a four-channel wavelength-division multiplexing (WDM) design while the Luxtera design is a four-channel integrated transceiver that uses a single laser and is tailored for 500m although Luxtera says it can achieve a 2km reach.

40 Gigabit Ethernet and Infiniband FDR

Avago Technologies announced that its eSR4 40 Gigabit Ethernet (GbE) QSFP+ has a reach of up to 550m, beyond the reach specified by the IEEE 40GBASE-SR4 standard. The eSR4 supports 40GbE or four independent 10GbE channels. When used as a multi-channel 10GbE interface, the QSFP+ interfaces to various 10GbE form factors such as X2, XFP and SFP+, It can also interface to a 100GbE CFP2, as mentioned.

Avago first announced the eSR4 QSFP+ with a reach of 300m over OM3 multi-mode fibre and 400m over OM4 fibre. The eSR4 now extends the reach to a guaranteed 550m when used with specific OM4 fibre from fibre makers Corning, Commscope and Panduit.

The extended reach is needed to address larger data centres now being build, as well as support flatter switch architectures that use two rather than three tiers of switches, and that have greater traffic flowing between switches on the same tier.

Avago says data centre managers are moving to deploy OM4 fibre. "The end user is going to move from OM3 to OM4 fibre for future-proofing purposes," says Tan. "The next-generation 32 Gig Fibre Channel and 100 Gigabit Ethernet are focussing on OM4 fibre."

Meanwhile, ColorChip showed its 56Gbps QSFP+ implementing the FDR (Fourteen Data Rate) 4x Infiniband standard as part of a Mellanox MetroX long-haul system demonstration at the show.

Finisar also demonstrated a 40Gbps QSFP using four 1310nm VCSELs. The result is a QSFP with a 10km reach that supports a 40Gbps link or four, 10Gbps links when used in a 'breakout' mode. The existing 40GBASE-LR4 standard supports a 40Gbps link only. Finisar's non-standard implementation adds a point-to-multipoint configuration.

"A single form factor port can be used not only for 40 Gig but also can enable higher density 10 Gig applications than what you can do with SFP+," says Ward.

Kaiam detailed a 40Gbps QSFP+ ER4 transceiver having a 40km reach. The QSFP+ transceiver has the equivalent functionality of four DML-based SFP+s fixed on a coarse WDM grid, and includes a wavelength multiplexer and de-multiplexer.

For OFC/NFOEC 2013 - Part 2, click here