ECOC 2015 Review - Final Part
Part 2 - Client-side component and module developments
- The first SWDM Alliance module shown
- More companies detail CWDM4, CLR4 and PSM4 mid-reach modules
- 400 Gig datacom technologies showcased
- The CFP8 MSA for 400 Gigabit Ethernet unveiled
The CFP MSA modules including the newest CFP8. Source: Finisar
- Lumentum and Kaiam use silicon photonics for mid-reach modules
- Finisar demonstrates a 10 km 25 Gig SFP28, and low-latency 25 Gig and 100 Gig SR4 interfaces
Shortwave wavelength-division multiplexing
Finisar demonstrated the first 100 gigabit shortwave wavelength-division multiplexing (SWDM) module at ECOC. Dubbed the SWDM4, the 100 gigabit interface supports WDM over multi-mode fibre. Finisar showed a 40 version at OFC earlier this year. “This product [the SWDM4] provides the next step in that upgrade path,” says Rafik Ward, vice president of marketing at Finisar.
The SWDM Alliance was formed in September to exploit the large amount of multi-mode fibre used by enterprises. The goal of the SWDM Alliance is to extend the use of multi-mode fibre by enabling link speeds beyond 10 gigabit.
“We believe if you can do something with multi-mode fibre, you can achieve cost points that are not achievable with single-mode fibre,” says Ward. “SWDM4 allows us to have not only low-cost optics on either end, but allows customers to reuse their installed fibre.”
The SWDM4 interface uses four 25 gigabit VCSELs operating at wavelengths sufficiently apart that cooling is not required. “By having this [wavelength] gap, you can keep to relatively low-cost components like for multiplexing and de-multiplexing,” says Ward.
The 100 Gig SWDM4 achieves 70 meters over OM3 fibre and 100 meters over OM4 fibre. SWDM can scale beyond 100 gigabit, says Ward, but the challenge with multi-mode fibre remains the tradeoff between speed and distance.
Finisar is already shipping SWDM4 alpha samples to customers.
The SWDM Alliance founding members include CommScope, Corning, Dell, Finisar, H3C, Huawei, Juniper Networks, Lumentum, and OFS.
CWDM4, CLR4 and PSM4
Oclaro detailed a 100 gigabit mid-reach QSFP28 module that supports both the CWDM4 multi-source agreement (MSA) and the CLR4 MSA. “We can support either depending on whether, on the host card, there is forward-error correction or not,” says Robert Blum, director of strategic marketing at Oclaro.
Both MSAs have a 2 km reach and use four 25 gigabit channels. However, the CWDM4 uses a more relaxed optical specification as its overall performance is complemented with forward-error correction (FEC) on the host card. The CLR4, in contrast, does not use FEC and therefore requires a more demanding optical specification.
“The requirements are significantly harder to meet for the CLR4 specification,” says Blum. By avoiding FEC, the CLR4 module benefits low-latency applications such as financial trading.
Oclaro showed its dual-MSA module achieving a 10 km reach at ECOC even though the two specifications call for 2 km only. “We have very large margins for the module compared to the specification,” says Blum, adding that customers now need to only qualify one module to meet their CWDM4 or CLR4 line card needs.
Other optical module vendors that announced support for CWDM4 in a QSFP28 module include Source Photonics, whose module is also CLR4-compliant. Kaiam is making CWDM4 and CLR4 modules using silicon photonics as part of its designs.
Lumentum also detailed its CWDM4 and the PSM4, a QSFP28 that uses a single-mode ribbon cable to deliver 100 Gig over 500 meters. Lumentum says its CWDM4 and PSM4 QSFP28 products will be available this quarter. “These 100 gigabit modules are what the hyper-scale data centre operators are clamouring for,” says Brandon Collings, CTO of Lumentum.
The question is who can ramp and support the 100 Gig deployments that are going to happen next year
Lumentum says it is using silicon photonics technology for one of its designs but has not said which. “We have both technologies [indium phosphide and silicon photonics], we use both technologies, and silicon photonics is involved with one of these [modules],” says Collings.
There is demand for both the PSM4 and CWDM4, says Lumentum. Which type a particular data centre operator chooses depends on such factors as what fibre they have or plan to deploy, whether they favour single-mode fibre pairs or ribbon cable, and if their reach requirements are beyond 500 meters.
Quite a few module companies have already sampled [100 Gig] products, says Oclaro’s Blum: “The question is who can ramp and support the 100 Gig deployments that are going to happen next year.”
Technologies for 400 gigabit
Several companies demonstrated technologies that will be needed for 400 gigabit client-side interfaces.
NeoPhotonics and chip company InPhi partnered to demonstrate the use of PAM-4 modulation to achieve 100 gigabit. “To do PAM-4, you need not only the optics but a special PAM-4 DSP,” says Ferris Lipscomb, vice president of marketing at NeoPhotonics.
The 400 Gigabit Ethernet standard under development by the IEEE 802.3bs supports several configurations using PAM-4 including a four-channel parallel single-mode fibre configuration, each at 100 gigabit that will have a 500m reach, and two 8 x 50 gigabit, for 2 km and 10 km links.
The company showcased its 4x28 Gig transmitter optical sub-assembly (TOSA) that uses a photonic integrated circuit comprising electro-absorptive modulated lasers (EMLs). Combined with InPhi’s PAM-4 chip, two channels were combined to achieve 100 gigabit. NeoPhotonics says its EMLs are also capable of supporting 56 gigabaud rates which, coupled with PAM-4, would achieve 100 gigabit single channels.
Lipscomb points out that not only are there several interfaces under development but also various optical form factors. “For 100 Gig and 400 Gig client-side data centre links, there are several competing MSA groups,” says Lipscomb. “The final winning approach has not yet emerged and NeoPhotonics wants its solution to be generic enough so that it supports this winning approach once it emerges.”
Meanwhile, Teraxion announced its silicon photonics-based modulator technology for 100 gigabit (4 x 25 Gig) and 400 gigabit datacom interfaces. “People we talk to are interested in WDM applications for short-reach links,” says Martin Guy, Teraxion’s CTO and strategic marketing.
Teraxion says a challenge using silicon photonics for WDM is supporting a broad band of wavelengths. “People use surface gratings to couple light into the silicon photonics,” says Guy. “But surface gratings have a strong wavelength-dependency over the C-band.”
Teraxion has developed an edge coupler instead which is on the same plane as the propagating light. This compares to a surface grating where light is coupled vertical to the plane.
You hear a lot about the cost of silicon photonics but one of the key advantages is the density you can achieve on the chip itself. Having many modulators in a very small footprint has value for the platform; you can make smaller and smaller transceivers.
“We can couple light efficiently with large-tolerance alignment and our approach can be used for WDM applications,” says Guy. Teraxion’s modulator array can be used for CWDM4 and CLR4 MSAs as well as optical engines for future 400 gigabit datacom systems.
“You hear a lot about the cost of silicon photonics but one of the key advantages is the density you can achieve on the chip itself,” says Guy. “Having many modulators in a very small footprint has value for the platform; you can make smaller and smaller transceivers.”
CFP8 MSA
Finisar demonstrated a 400 gigabit link that included a mock-up of the CFP8 form factor, the latest CFP MSA member being developed to support emerging standards such as 400 Gigabit Ethernet.
The 400 gigabit demonstration implemented the 400GE-SR16 multi-mode standard. A Xilinx FPGA was used to implement an Ethernet MAC and generated 16, 25 Gig channels that were fed to four CFP4 modules, each implementing a 100GBASE-SR4 but collectively acting as the equivalent of the 400GE-SR16. The 16 fibre outputs were then fed to the CFP8 prototype which performed an optical loop-back function, sending the signals back to the CFP4s and FPGA.
The CFP8 will be able to support 6.4 terabit of switching on a 1U card when used in a 2 row by 8 module configuration. The CFP8 has a similar size and power consumption profile of the CFP2. “There is still a lot of work putting an MSA together for 400 gigabit,” says Ward, adding that there is still no timeframe as to when the CFP8 MSA will be completed.
25 Gig SFP28
Finisar also announced at ECOC a 1310nm SFP28 supporting 25 gigabit Ethernet over 10 km, complementing the 850nm SFP28 short reach module it announced at OFC 2015.
Ethernet vendors are designing their next-generation series of switches that use the SFP28, says Finisar, while the IEEE is completing standardising 25 Gigabit Rthernet over copper and multi-mode fibre options.
“There hasn’t yet been a motion to standardise a long-wave interface,” says Ward. “With the demo at ECOC, we have come out with a 25 Gig long-wave interface in advance of a standard.”
Ward points out that the large-scale data centres several years ago only had 40 gigabit as a higher speed option beyond 10 gigabit. Now enterprises will also have a 25 gigabit option.
Ward points out that 25 gigabit compared to 40 Gig delivers an attractive cost-performance. Forty gigabit short-reach and long-reach interfaces are based on four channels at 10 gigabit, whereas 25 gigabit uses one laser and one photo-detector that fit in an SFP28. This compares to a QSFP for 40 Gig.
“25 Gigabit Ethernet is a very interesting interface for the next set of customers after the Web 2.0 players that are looking to migrate beyond 10 gigabit,” said Ward.
Low-latency 25 Gig SR and 100 Gig Ethernet SR4 modules
Also announced by Finisar are 25 Gigabit Ethernet SFP28 SR and 100GE QSFP28 SR4 transceivers that can operate without accompanying FEC on the host board. The transceivers achieve a 30 meter reach on OM3 fibre and 40 meters using OM4 fibre.
“Using FEC simplifies the optical link,” says Ward. “It can take the cost out of the optics by having FEC which gives you additional gain.” But some customers have requested the parts for use without FEC to reduce link latency, similar to those that choose the CLR4 MSA for mid-reach 100 Gig.
Finisar has not redesigned its modules but offering modules that have its higher performing VCSELs and photo-detectors. “Think of it as a simple screen,” says Ward.
Click here for the ECOC 2015 Review - Part 1.
OFC 2014 product round-up - Final part
The industry is moving at a clip to fill the void in 100 Gig IEEE standards for 100m to 2km links. Until now, the IEEE 10km 100GBASE-LR4 and the 10x10 MSA have been the interfaces used to address such spans.
But responding to data centre operators, optical players are busy developing less costly, mid-reach MSAs, as was evident at the OFC exhibition and conference, held in San Francisco in March.
Meanwhile, existing IEEE 100 Gigabit standards are skipping to the most compact CFP4 and QSFP28 form factors. The -LR4 standard was first announced in a CFP in 2010, and moved to the CFP2, half the size of the CFP, in 2013. Now, several companies have detailed CFP4 -LR4 products, while Source Photonics has gone one better, announcing the standard in a QSFP28.
The CFP4 is half the size of the CFP2, while the QSFP28 is marginally smaller than the CFP4 but has a lower power consumption: 3.5W compared to the CFP4's 6W.
Timeline of some pluggable announcements at recent OFCs. Source: Gazettabyte
The mid-reach landscape
Several interfaces for mid-reach interconnect were detailed at OFC. And since the show, two MSAs have been detailed: the CWDM4 and the CLR4 Alliance.
At OFC, the OpenOptics MSA backed by Mellanox Technologies and Ranovus, was announced. Skorpios Technologies demoed its CLR4 module that has since become the CLR4 Alliance. And vendors discussed the Parallel Single Mode (PSM4) initiative that was first detailed in January.
Switch vendor Mellanox Technologies and module start-up Ranovus announced the OpenOptics MSA at OFC. The QSFP-based MSA uses a single-mode fibre and WDM transmission around 1550nm to address data centre links up to 2km.
Saeid Aramideh of Ranovus says that the MSA using its laser and silicon photonics technologies will deliver significant cost, power and size advantages {add link}. "But the 1550nm WDM connection is open to any technology," says Aramideh, chief marketing and sales officer at Ranovus. "It does not have to be silicon photonics."
The first MSA product, a 100 Gig QSFP28, uses 4x25 Gig channels. "The channel spacing for the MSA is flexible to be 50GHz or more," says Aramideh. The MSA is scalable to 400 Gig and greater rates. The 100 Gig QSFP28 technology is several months away from sampling.
Skorpios Technologies demonstrated its QSFP28-CLR4 transceiver although the details of the MSA have yet to be detailed. Skorpios is a silicon photonics player and uses heterogenous integration where the lasers, modulators, detectors and optical multiplexer and de-multiplexer are monolithically integrated on one chip.
The PSM4 MSA is another initiative designed to tackle the gap between IEEE short and long reach standards. Backed by players such as Avago Technologies, Brocade, JDSU, Luxtera, Oclaro, and Panduit, the 100 Gig standard is defined to operate in the 1295-1325nm spectral window and will have a reach of at least 500m.
ColorChip demonstrated a 100 Gig (4x25 Gig) QSFP28 with a 2km reach at the show. The design uses uncooled directly modulated lasers to achieve the 3.5W power consumption. Since the show Colorchip is one of the member companies backing the CLR4 Alliance and the demoed QSFP matches the first details of the new MSA's spec.
100GBASE-LR4 moves to CFP4 and QSFP28
The IEEE 100GBASE-LR4 standard is transitioning to the smallest modules. At OFC, vendors detailed the first CFP4s while Source Photonics announced the -LR4 in a QSFP28.
Source Photonics says its transceiver consumes 3.5W. The QSFP28 form factor achieves up to a fourfold increase in face plate density compared to the CFP2: up to 48 modules compared to a dozen CFP2 modules, says the company, which expects first QSFP28 -LR4 samples in mid-2014.
Meanwhile, Avago Technologies, Finisar, Fujitsu Optical Components and JDSU all detailed their first CFP4 -LR4 modules.
JDSU says that when it developed the optics for its CFP2 -LR4, it was already eyeing the transition to the CFP4 and QSFP28 form factors. To achieve the -LR4 spec in the 6W CFP4, a key focus are the clock data recover (CDR), driver and trans-impedance amplifier chips. "A decent amount of the power consumption is wrapped up in the ICs that do the CDR and a variety of the digital functions behind the photonics," says Brandon Collings, JDSU's CTO for communications and commercial optical products. JDSU expects general availability of its CFP4 -LR4 later this year.
Finisar's -LR4 is its second CFP4 product; at ECOC 2013 it showcased a 100m, 100GBASE-SR4 CFP4. Finisar says its -LR4 uses distributed feedback (DFB) lasers and consumes 4.5W, well within the CFP4's 6W power profile. At OFC, the CFP4 was demonstrated working with CFP2 and CFP -LR4 modules. Finisar's CFP4 will sample later this year.
Avago announced availability of its -LR4 transmit optical subassembly (TOSA) and receive optical subassembly (ROSA) products for the CFP4, along with its CFP4 module which it says will be available next year. Fujitsu Optical Components also used OFC to demo its CFP4 -LR4.
40km Extended Reach Lite
Oclaro and Finisar detailed a tweak to the 100 Gig Extended Reach standard: the 40km, 100GBASE-ER4.
The IEEE standard uses a power-hungry semiconductor optical amplifier (SOA) prior to the PIN photodetector to achieve 40km. The module vendors have proposed replacing the SOA and PIN with an avalanche photo diode (APD) and external forward error correction to reduce the power consumption while maintaining the optical link budget. The changed spec is dubbed 100GBASE-ER4 Lite.
"Trying to achieve the power envelopes required for the CFP4 and QSFP28 using SOAs is going to be too hard," says Kevin Granucci, vice president of strategy and marketing at Oclaro.
Oclaro demonstrated a ER4-Lite in a CFP2. The module supports 100 Gigabit Ethernet and the Optical Transport Network (OTN) OTU-4 rates, and consumes less than 9W. "We are using the CFP2 as the first proof-of-concept," says Granucci. "For the 6W CFP4 and the 3.5W QSFP28, we think this is the only solution available."
At OFC Finisar demonstrated the link's feasibility, which it refers to as ER4f, using four 28 Gig lasers and four 28 Gig APDs.
Oclaro says it is seeing customer interest in the ER4 Lite, and points out that there are many 10 Gig 40km links deployed, especially in China. "The ER4 Lite will provide an update path to 100 Gig," says Granucci.
VCSELs: serial 40 Gig and the 400 Gig CDFP
Finisar showcased a VCSEL operating at 40 Gig at OFC. State-of-the-art VCSEL interfaces run up to 28 Gig. Finisar's VCSEL demonstration was to show the commercial viability of higher-speed VCSELs for single channel or parallel-array applications. "We believe that VCSELs have not run out of steam," says Rafik Ward, vice president of marketing at Finisar. The 40 Gig VCSEL demonstration used non-return-to-zero (NRZ) signalling, "no higher-order modulation is being used", says Ward.
IBM T.J.Watson Research Center has published an IEEE paper with Finisar involving a 56Gbps optical link based on an 850nm VCSEL.
Finisar also demonstrated an CDFP-based active optical cable. The CDFP is a 400 Gig MSA that uses 16 x 25 Gig VCSEL channels in each direction. Such an interface will address routing, high-performance computing and proprietary interface requirements, says Finisar. The demonstration showcased the technology; Finisar has yet to announce interface products or reaches.
Short reach 100G and 4x16 Gig Fibre QSFPs
Avago Technologies announced a 100GBASE-SR4 implemented using the QSFP28. Avago's I Hsing Tan, segment marketing manager for Ethernet and storage optical transceivers, says there has been a significant ramp in data centre demand for the 40GBASE-SR4 QSFP+ in the last year. "Moving to the next generation, the data centre operator would like to keep the same [switch] density as the QSFP+, and the QSFP28 MSA offers the same form factor," he says.
The QSFP28 differs from the QSFP+ is that its electrical connector is upgraded to handle 28 Gigabit-per-lane data rates. Avago says the -SR4 module will be generally available next year.
Avago also announced a 4x16 Gigabit Fibre Channel QSFP+ transceiver. The industry is transitioning from 8 to 16 Gig Fibre Channel, says Avago, and this will be followed by 32 Gig serial and 4x32 Gig Fibre Channel modules.
The company has announced a 4x16 Gig QSFP+ to continue the increase in platform channel density while the industry transitions from 16 to 32 Gig Fibre Channel. "This solution is going to provide the switch vendor a 3x increase in density at half the power dissipation per channel for 16 Gig Fibre Channel, before the 32 bit Fibre Channel come to maturity in three to five years," says Tan.
Avago has just announced that it has shipped over half a million QSFP+ modules.
Optical engines
TE Connectivity announced its 25 Gig-per-channel optical engine technology. The Coolbit optical engine will be included in four TE Connectivity products planned for this year: 100 Gig QSFP28 active optical cables (AOCs), 100 Gig QSFP28 transceivers, 300 Gig mid-board optical modules, and 400 Gig CDFP AOCs.
Meanwhile, Avago's MiniPod and MicroPod optical engine products now have a reach of 550m when coupled with Corning's ClearCurve OM4 fibre.
"This allows customers in the data centre to go a little bit further and not have to go to single-mode fibre," says Sharon Hall, product line manager for embedded optics at Avago.
For Part 1, click here
Further reading:-
TE Connectivity White Paper: End-to-end Communications with Fiber Optic Technologies, click here
LightCounting: Reflections on OFC 2014: The industry is approaching a critical junction, click here
Ovum at OFC 2014, click here
LightWave OFC 2014 Podcast, click here
Ethernet Alliance Blog: OFC 2014 show and best in class, click here