Alcatel-Lucent reveals its 100Gbps-coherent hand
“It would be irresponsible of any system vendor to overlook a solution that can bring a cost advantage to their customer”
Sam Bucci, Alcatel-Lucent
What is being announced?
- Alcatel-Lucent has a commercially available 100Gbps optical transmission system.
- 40Gbps coherent transmission is also supported.
- Implemented as part of the 1830 Photonic Service Switch (PSS), the platform has a capacity of 500 Gigabit-per-second (Gbps) per rack, or a bay – made up of three racks – capacity of 1.5 Terabit-per-second.
- The system specification includes 88, 100Gbps dense wavelength division multiplexing (DWDM) lightpaths at 50GHz spacing that span the extended C-band; a reach of between 1,500 and 2,000km using coherent-optimised optical amplifiers, and the ability to operate alongside existing 10 and 40Gbps wavelengths without needing a guard-band between them (for more detail, click here).
- Some 20 operators are lined up to trial the 100Gbps technology. These include operators that have deployed the 1830 PSS and new ones.
- Telefònica and Softbank Telecom are two operators known to be trialling the 100Gbps system, Alcatel-Lucent will announce a third next week.
Why is the announcement important?
Alcatel-Lucent is the latest system vendor to announce a commercially available 100Gbps system. Until now Nortel’s Metro Ethernet Networks unit, now owned by Ciena, and Ciena itself had commercially available systems. Indeed Verizon Business deployed Nortel’s 100Gbps system for a route linking Paris and Frankfurt in late 2009.
"What will be a significant differentiator is the control/ management plane interworking across platforms - the integration of IP MPLS with optical networking products."
Ron Kline, Ovum
Alcatel-Lucent claims to be the first vendor to offer a 100Gbps system using a single carrier. Ciena/Nortel’s current offering is an extension of its 40Gbps coherent system and uses two 50Gbps sub-carriers that fit into a 50GHz channel.
But analysts downplay the significance of the advent of a 100Gbps single-carrier system. “Technology leads are short-lived,” says Ron Kline, principal analyst, network infrastructure at Ovum. "I’m not sure if there is a preference between single- versus dual-carrier from service providers either.”
What will be a significant differentiator, says Kline, is the control/ management plane interworking across platforms - the integration of IP MPLS with optical networking products. “Alcatel-Lucent is one of the few vendors which do both well and may have an edge pulling it off,” he says.
Ovum’s Dana Cooperson thinks it is significant that, like Ciena, and unlike some others, Alcatel-Lucent is also doing 40Gbps coherent. “I’ve heard some folks say they think 40 Gig coherent isn’t going anywhere, but the reasoning hasn’t made sense to me,” says Cooperson, Ovum’s vice president, network infrastructure. “If you have bad fibre, which loads of carriers do, and you want a mixed channel capability, which all carriers do, you’ll expect to get both in the same product.”
What’s been done?
Alcatel-Lucent’s 100Gbps system implements polarisation multiplexing quadrature phase-shift keying (PM-QPSK) modulation with coherent detection. The coherent receiver is based on an in-house application specific integrated circuit (ASIC) that includes high-speed analogue-to-digital (a/d) converters and a digital signal processor (DSP).
Alcatel-Lucent would not say if the ASIC uses a 60nm or 45nm CMOS process or what the sampling rate of its a/d converters are but it did say that it has built-in sufficient headroom to operate at a 64Gsamples-per-second rate. The system also uses hard-decision forward error correction (FEC) but, according to Sam Bucci, vice president, terrestrial portfolio management at Alcatel-Lucent, it is looking at a soft decision FEC scheme for a future version “that is not too far away”.
Additional system performance characteristics, according to Bucci, include the ability for the lightpath to travel through as many as 20 reconfigurable optical add/drop multiplexers (ROADMs) before needing optical-electrical-optical (OEO) conversion. The system also has a tolerance of at least 30ps for polarisation mode dispersion and 60,000 ps/nm for chromatic dispersion, says Bucci.
For 40Gbps coherent transmission, Alcatel-Lucent is using polarisation multiplexing binary phase-shift keying (PM-BPSK). Since less information is encoded on the symbol streams, this is a more demanding implementation because the implementation operates at 20Gbaud-per-second rather than the 10Gbaud-per-second of 40Gbps PM-QPSK coherent systems.“We were looking for a solution that was applicable not just for terrestrial but for submarine,” says Bucci. “Therefore the reach we were looking to achieve was greater than perhaps could be accomplished by other modulation formats.”
Alcatel-Lucent says PM-BPSK is also better able to withstand non-linear effects such as cross-phase modulation.
Is Alcatel-Lucent open to adopting an ASIC from a third-party developer for its future 100Gbps systems? “It would be irresponsible of any system vendor to overlook a solution that can bring a cost advantage to their customer,” says Bucci. “If there is a solution that can fit into the scheme we have developed, then yes, we would have to consider it if it produces an economic advantage.” Such an 'economic advantage' would have to be significantly more than just a 10 percent cost-saving, he says.
Volume production of the 100Gbps system will begin at the end of June 2010. Two client-side interface boards are available: a 10x10Gbps and a 100Gbps native port using a pluggable CFP transceiver.
The InfiniBand roadmap gets redrawn
“We can already demonstrate in silicon a 30Gbps transmitter."
Marek Tlalka, Luxtera
“Our June 2008 roadmap originally projected 4x EDR at less than 80Gbps data rate for 2011,” says Skip Jones, director of technology at QLogic and co-chair of the IBTA’s marketing working group. “The IBTA has increased the data speeds for 2011 due to demand for higher throughput.” A 26Gbps channel rate - or 104Gbps for 4x EDR - is to accommodate the overhead associated with 64/66bit encoding.
The IBTA has also added an interim speed, dubbed Fourteen Data Rate (FDR), operating at 14Gbps per channel or 56Gbps for 4x FDR. This, says the IBTA, is to address midrange enterprise applications in the data centre. “Many server OEMs’ backplanes can support speeds up to 56Gbps,” says Jones. “For those OEMs doing a server refresh using existing backplanes, 56Gbps will be the solution they’ll be looking to implement.”
The IBTA dismisses claims by some industry voices that the re-jigged roadmap is to stop InfiniBand falling behind 100 Gigabit Ethernet (GbE) while FDR is to advance InfiniBand while laser vendors grapple with the challenge of developing 26Gbps vertical-cavity surface-emitting lasers (VCSELs) for EDR.
Jones points out that 4x Quad Data Rate (QDR) InfiniBand (4x10Gbps) now accounts for between 60 and 70 percent of newly deployed InfiniBand systems, and that 100Gbps EDR will appear in 2011/ 2012. “The IBTA has a good track record of releasing products on time; as such, 100Gbps InfiniBand will come out much faster than 100 Gigabit Ethernet.” FDR, meanwhile, will benefit from 14Gbps VCSELs for Fibre Channel that will be available next year. Jones admits that developing a 26Gbps VCSEL poses a challenge but that “InfiniBand markets are mostly electrical interconnects”.
“The 4x25G short reach is not going to rise and dominate for quite awhile."
Scott Schube, LightCounting
“VCSELs are going to have a tough time at 26Gbps per lane, though they'll get there,” says Scott Schube, senior analyst and strategist at optical transceiver market research firm, LightCounting. “There's definitely a push to go to 26Gbps per lane to reduce pin counts, and the chip guys look like they will be ready before the VCSELs.”
One company looking to benefit from the emerging market for EDR is Luxtera. The silicon photonics specialist says its modulator has already been demonstrated at 30Gbps. This is fast enough to accommodate EDR, 100 Gigabit Ethernet (a 4-channel design) and the emerging 28Gbps Fibre Channel standard.
“We can already demonstrate in silicon a 30Gbps transmitter using the same laser as in our existing products and modulated in our silicon waveguides,” says Marek Tlalka, vice president of marketing at Luxtera. “That allows us to cover 14Gbps, 26Gbps EDR, parallel Ethernet as well as 28Gbps for serial Fibre Channel.”
Luxtera will need to redesign the transistor circuitry to drive the modulator beyond the current 15Gbps before the design can be brought to market. It will also use an existing silicon modulator design though the company says some optimisation work will be required.
There are two main product offerings from Luxtera: QSFP-based active optical cables and OptoPHY, one and four-channel optical engines. Luxtera’s OptoPHY product is currently being qualified and is not yet in volume production.
For multi-channel designs, Luxtera uses a continuous-wave 1490nm distributed feedback (DFB) laser fed to the modulated channels. Addressing 28Gbps Fibre Channel, an SFP+ form factor will be used. Luxtera may offer a transceiver product or partner with a module maker with Luxtera providing the optical engine. “It’s an open question,” says Tlalka.
“The IBTA has a good track record of releasing products on time; as such, 100Gbps InfiniBand will come out much faster than 100 Gigabit Ethernet.”
Skip Jones, IBTA
The company has said that the single-channel and four-channel 10Gbps OptoPHY engine consumes 450mW and 800mW respectively. Going to 26Gbps will increase the power consumption but only by several tens of percent, it says.
The first product from Luxtera will be a pluggable cable followed by a companion OptoPHY. The pluggable active optical cable from Luxtera will support 100GbE and EDR Infiniband. “I’d still place my bets on InfiniBand deploying first followed by 100GbE,” says Tlalka.
But Schube warns that Luxtera faces a fundamental challenge “Leading-edge designs based on proprietary technology to solve commodity problems - more bandwidth for out-of-the-box connections - are never going to get widely adopted, though Luxtera can fill a niche for awhile," he says.
There is also much work to be done before 100Gbps interfaces will be deployed. “The 4x25G short reach is not going to rise and dominate for quite awhile, no matter what the component availability is,” says Schube. That is because switch ASICs, backplanes, connectors and line cards will all first need to be redesigned.
Meanwhile the IBTA has also announced two future placeholder data rates on its InfiniBand roadmap: High Data Rate (HDR) due in 2014 and the Next Data Rate (NDR) sometime after. “We will refrain from identifying the exact lane speed until we are closer to that timeframe to avoid confusion and the possibility - and probability - of changing future lane speeds,” says Jones.
And Luxtera says its modulator can go faster still. “I think we can easily go 40 and 50Gbps,” says Tlalka. “After 50Gbps we’ll have to look at new magic.”
Ciena post-MEN
“The 40G and 100G technology were key to the deal and we made sure that the core team was still there”
Tom Mock, Ciena
The company has announced the CN 5150 service aggregation switch, added Nortel’s 40 Gigabit-per-seconds (Gbps) coherent transmission technology to its flagship CN 4200 platform, and announced 140 job cuts, mostly in Europe. US operator AT&T has also selected the company as one of two suppliers of its optical and transport equipment.
Ciena provides optical transport, optical switching and Carrier Ethernet equipment. “We were finding it difficult to fund the required R&D in all three segments,” says Tom Mock, senior vice president of strategic planning at Ciena. “We saw this [the MEN acquisition] as an opportunity to bring good technology on board and give the company the scale needed to execute in these technology areas.”
According to Mock, Ciena was one of several firms interested in the Nortel unit but that Nokia Siemens Networks was the main counter-bidder in the auction process. Ciena won after agreeing to pay US $773.8 million, gaining MEN’s R&D group and associated sales and marketing.
In particular, it gained the R&D for optical transport – Nortel’s Optical Multiservice Edge (OME) 6500 product line for 40Gbps and 100Gbps, the Optical Metro 5200 metro and enterprise platform, Carrier Ethernet, and the R&D for software and network management. Most of these activities are based in Ottawa, Ontario.
“We had pretty good solutions in optical switching and carrier Ethernet but we were looking for a stronger transport offering, which is what Nortel brought to us,” says Mock. The acquisition, which effectively doubles the company’s size, means that Ciena now plays in a “$18 billion sandbox” comprising optical networking and Ethernet transport and services, according to market research firm Ovum.
Did Ciena secure Nortel’s MEN’s key staff, given the lengthy period – over a year – to complete the acquisition? “We agreed with Nortel that we would get 2000 staff out of a total of 2300 staff,” says Mock.
Yet Ciena had no visibility regarding staff since Nortel remained a competitor until the deal was completed. “We were very pleasantly surprised at the quality of the people who were in MEN,” says Mock. “When companies are in hard times the best people begin to leave, and because of the uncertainty I’m sure some people did leave.”
Ciena claims it secured MEN’s core 40 and 100Gbps team despite announcements such as Infinera's that it had recruited John McNicol, a senior engineer involved in the development of Nortel’s coherent technology. “The 40G and 100G technology were key to the deal and we made sure that the core team was still there,” says Mock.
He also dismisses the view that Nortel’s 100Gbps coherent technology market lead has been eroded due to the uncertainty. Mock claims it has a 12- to 18-month lead and points to Verizon Business’ deployment of Nortel’s 100Gbps system in late 2009 as proof that MEN continued to push the technology.
Strategy
Ciena’s primary focus is on what it calls carrier optical Ethernet, described by Mock as the marrying of the capacity scaling and reliability of optical transport with the ubiquity, flexibility and economics of Ethernet.
For Ciena this translates to three main product lines:
- Packet optical transport, primarily optical transport with some aggregation.
- Packet optical switching based on Ciena’s CoreDirector platform with its time-division multiplexing (TDM) and Ethernet switching, as well as control plane technology.
- Carrier Ethernet service delivery.
According to Ovum, Ciena is now the third “billion dollar club” optical networking vendor member with a 9% market share, behind Huawei and Alcatel-Lucent, with 24% and 19%, respectively. It also becomes the North American leader, with a 20% share while improving its standing in all other regional markets. In contrast, for Ethernet the combined company had only 3% share in 2009. “We are emerging as a leader in the Carrier Ethernet space,” claims Mock. “In 4Q 2009 we were leading in North America, according to Heavy Reading.”
Ciena sees optical transport and switching blurring but says that most of its customers still see these as separate products. “Both our packet optical switching and packet optical transport platforms can be used in these applications, for example the OME 6500 is looked at as a transport device but it has TDM and packet switching as well,” says Mock. But with time Ciena says optical switching and optical transport product families will increasingly consolidate.
What next?
Having completed the deal, one of the first things Ciena did was determine its product portfolio and tell its operator customers its plans.
Issues set to preoccupy Ciena for the next 12 to 18 months include the integration of Nortel’s 40Gbps and 100Gbps technology onto Ciena’s transport and switching platforms, getting the control plane of Ciena’s switching product integrated onto Nortel’s products, and bringing all the products under common network management.
At OFC/ NFOEC 2010 Ciena showcased Nortel’s OME 6500 transmitting over Ciena’s CN 4200 line system with both being overseen by Ciena’s OnCenter management software. “I wouldn’t point to the network management integration as a finished product but a step along the path,” says Mock.
According to Ovum, the demonstrations included 100Gbps over 1,500km of Corning ultra-low-loss fiber, 100Gbps over 800km in the presence of large and fast polarisation mode dispersion transients, and 40Gbps ultra-long haul transmission over 3,500km.
Ciena has said it expects its business to grow at least at the market rate: 10 to 12 percent yearly.
AT&T domain supplier
In April, AT&T announced that it had selected Ciena as a domain supplier. AT&T's domain supplier programme involves the operator splitting its networking requirements across several technologies, choosing two players for each domain. AT&T plans to work closely with each domain supplier ensuring that AT&T gains equipment tailored to its requirements while vendors such as Ciena can focus their R&D spending by seeing early the operator’s roadmap.
Did Ciena acquire Nortel to become a domain partner? “We would not make an acquisition to win the business of any one carrier,” says Mock. “But we realised that if we going to be a significant player in next-generation infrastructure we needed a certain critical mass, in portfolio and market coverage globally.
“Did we get selected because of Nortel, it’s hard to say – I’m sure it didn’t hurt - but we've been a supplier to AT&T for 10 years,” says Mock. He also highlights the operator’s own announcement to explain Ciena’s selection: “They talk about two technologies in particular – 100Gbps technology and Optical Transport Networking (OTN).”
Ovum argues in its “Telecoms in 2020: network infrastructure” report that the future prospects of specialist vendors will be as rosy as full-service ones. “We do view ourselves as specialists even though we’ve essentially doubled the size of the company, and there is absolutely a place for specialist companies as they are genuinely more agile,” says Mock.
Mock also expects further system vendor consolidation. “Optical transport remains fragmented so there are opportunities for further consolidation,” he says. Fragmented in what way? “If you look at the router space there are two dominant players, in optical transport there are 10 – no-one has a 40 to 50 percent market share.”
Infinera PICs 100Gbps coherent
Infinera is expediting its product plans, basing its optical transmission roadmap on coherent detection.
The company plans to launch a 100Gbps coherent transmission system in 2012. The design will be based on a pair of 5x100Gbps ultra-long-haul photonic integrated circuit (PIC) chips that will enable its systems to deliver 8 Terabits-per-second (Tbps) over a fibre.
“This change in roadmap is because of the successful development of our 100G coherent ASIC programme, and we have integrated five 100Gbps coherent channels onto one card.”
Drew Perkins, Infinera
Infinera also announced that it will be adding 40Gbps coherent detection to its DTN system in 2011. The 40Gbps will be based on optical modules and not its PIC technology. Using its planar technology and working with optical module suppliers to integrate its in-house coherent technology, Infinera’s DTN system will support 25GHz channel spacings to cram 160 lightpaths across the C-band, to deliver 6.4Tbps capacity.
Why is the announcement important?
Infinera had still to launch its 10x40Gbps PIC. This announcement marks a shift in Infinera’s strategy to focus on 100Gbps and gain a technology edge by offering the highest line speed at an unmatched density.
“It’s a good roadmap for Infinera,” says Jimmy Yu, a director at the Dell'Oro Group. “From an optical market perspective, I think 2012 is the right time for having a 100Gbps DWDM long-haul system. And it'll definitely be coherent.”
Dell’Oro expects to see early adopters of 100Gbps in 2010 and 2011, but it will be 2012/2013 when the market for 100Gbps will ramp.
What has motivated Infinera’s shift has been its success in developing coherent technology, says Drew Perkins, Infinera’s CTO. Coherent technology in combination with PICs is the best of all worlds, he says, marrying the two most significant optical developments of the last decade.
Perkins admits Infinera has been slow in offering 40Gbps technology.
“We are late to a very small market,” he says. “We think there is a 40G squeeze going on – it took the industry so long to get 40Gbps right with coherent technology such that 100Gbps is now just around the corner, as we are proving here.”
Yet Infinera will offer 40Gbps next year and will seek to differentiate itself with 25GHz channel spacing. “But it [the 40Gbps design] will be rapidly superseded by our 100Gbps, 8Tbps technology and then we believe we will be early to market with 100Gbps,” says Perkins.
Dell’Oro says 40Gbps is growing rapidly and it expects continued growing. “In 2009, 40Gbps wavelength shipments grew a little over 160 percent, and we’re forecasting it to grow nearly 90 percent in 2010,” says Yu. “If Infinera delivers 40Gbps on 25GHz channel spacing, it'll be a good interim step to 100Gbps.”
What’s being done?
Infinera has now scrapped its 10x40Gbps differential quadrature phase-shift keying (DQPSK) PIC, going to a 5x100Gbps polarisation multiplexing quadrature phase-shift keying (PM-QPSK) design instead. Interestingly, Perkins says that the 10x40Gbps transmitter PIC was designed from the start to also support 5x100Gbps PM-QPSK modulation.
The challenge is designing the coherent receiver PIC which is significantly different, and has required Infinera to gain coherent expertise in-house.
The receiver PIC also requires a local oscillator laser. “We have integrated the laser onto the receiver PIC per channel,” says Perkins. Infinera’s PICs already use lasers that are tuned over a significant number of channels though not the whole C-band so this is using technology it already has.
Another key aspect of the coherent receiver is the associated electronics that comprises very high-speed A/D converters, a digital signal processor and most likely advanced forward error correction. Developing such an ASIC is a significant challenge.
Is Infinera developing such a design? Infinera points to its Ottawa, Ontario-based research facility that was announced in September last year. “That team is working on ASIC level coherent technology,” says Perkins. “This change in roadmap is because of the successful development of our 100G coherent ASIC programme, and we have integrated five 100Gbps coherent channels onto one card.”
Did Infinera consider designing a 10x100Gbps PIC? “It comes down to the size of the line card,” says Perkins. Infinera believes the resulting terabit line card would have been too large a jump for the industry given the status of associated electronics such as switching technology.
What next?
Infinera says that in 2012 it will ship systems based on its 100Gbps coherent PICs to customers but it is unwilling to detail the key development milestones involved between now and then.
As for future product developments, Infinera claims it can extend overall capacity of its coherent technology in several directions.
It says it can integrate 10, 100Gbps channels onto a PIC. “Somewhere in the future we undoubtedly will”, says Perkins. The company also states that in the “fullness of time” it could deliver 100Gbps over 25GHz channel spacings.
Perkins also reconfirmed that Infinera will continue to advance the modulation scheme used, going from QPSK to include higher order quadrature amplitude modulation (QAM) schemes.
Optical transmission beyond 100Gbps
Part 3: What's next?
Given the 100 Gigabit-per-second (Gbps) optical transmission market is only expected to take off from 2013, addressing what comes next seems premature. Yet operators and system vendors have been discussing just this issue for at least six months.
And while it is far too early to talk of industry consensus, all agree that optical transmission is becoming increasingly complex. As Karen Liu, vice president, components and video technologies at market research firm Ovum, observed at OFC 2010, bandwidth on the fibre is no longer plentiful.
“We need to keep a very close eye that we are not creating more problems than we are solving.”
Brandon Collings, JDS Uniphase.
As to how best to extend a fibre’s capacity beyond 80, 100Gbps dense wavelength division multiplexing (DWDM) channels spaced 50GHz apart, all options are open.
“What comes after 100Gbps is an extremely complicated question,” says Brandon Collings, CTO of JDS Uniphase’s consumer and commercial optical products division. “It smells like it will entail every aspect of network engineering.”
Ciena believes that if operators are to exploit future high-speed transmission schemes, new architected links will be needed. The rigid networking constraints imposed on 40 and 100Gbps to operate over existing 10Gbps networks will need to be scrapped.
“It will involve a much broader consideration in the way you build optical systems,” says Joe Berthold, Ciena’s vice president of network architecture. “For the next step it is not possible [to use existing 10Gbps links]; no-one can magically make it happen.”
Lightpaths faster than 100Gbps simply cannot match the performance of current optical systems when passing through multiple reconfigurable optical add/drop multiplexer (ROADM) stages using existing amplifier chains and 50GHz channels.
Increasing traffic capacity thus implies re-architecting DWDM links. “Whatever the solution is it will have to be cheap,” says Berthold. This explains why the Optical Internetworking Forum (OIF) has already started a work group comprising operators and vendors to align objectives for line rates above 100Gbps.
If new links are put in then changing the amplifier types and even their spacing becomes possible, as is the use of newer fibre. “If you stay with conventional EDFAs and dispersion managed links, you will not reach ultimate performance,” says Jörg-Peter Elbers, vice president, advanced technology at ADVA Optical Networking,
Capacity-boosting techniques
Achieve higher speeds while matching the reach of current links will require a mixture of techniques. Besides redesigning the links, modulation schemes can be extended and new approaches used such as going ‘gridless” and exploiting sophisticated forward error-correction (FEC) schemes.
For 100Gbps, polarisation and phase modulation in the form of dual polarization, quadrature phase-shift keying (DP-QPSK) is used. By adding amplitude modulation, quadrature amplitude modulation (QAM) schemes can be extended to include 16-QAM, 64-QAM and even 256 QAM.
Alcatel-Lucent is one firm already exploring QAM schemes but describes improving spectral efficiency using such schemes as a law of diminishing returns. For example, 448Gbps based on 64-QAM achieves a bandwidth of 37GHz and a sampling rate of 74 Gsamples/s but requires use of high-resolution A/D converters. “This is very, very challenging,” says Sam Bucci, vice president, optical portfolio management at Alcatel-Lucent.
Infinera is also eyeing QAM to extend the data performance of its 10-channel photonic integrated circuits (PICs). Its roadmap goes from today’s 100Gbps to 4Tbps per PIC.
Infinera has already announced a 10x40Gbps PIC and says it can squeeze 160 such channels in the C-band using 25GHz channel spacing. To achieve 1 Terabit would require a 10x100Gbps PIC.
How would it get to 2Tbps and 4Tbps? “Using advanced modulation technology; climbing up the QAM ladder,” says Drew Perkins, Infinera’s CTO.
Glenn Wellbrock, director of backbone network design at Verizon Business, says it is already very active in exploring rates beyond 100Gbps as any future rate will have a huge impact on the infrastructure. “No one expects ultra-long-haul at greater than 100Gbps using 16-QAM,” says Wellbrock.
Another modulation approach being considered is orthogonal frequency-division multiplexing (OFDM). “At 100Gbps, OFDM and the single-carrier approach [DP-QPSK] have the same spectral efficiency,” says Jonathan Lacey, CEO of Ofidium. “But with OFDM, it’s easy to take the next step in spectral efficiency – required for higher data rates - and it has higher tolerance to filtering and polarisation-dependent loss.”
One idea under consideration is going “gridless”, eliminating the standard ITU wavelength grid altogether or using different sized bands, each made up of increments of narrow 25GHz ones. “This is just in the discussion phase so both options are possible,” says Berthold, who estimates that a gridless approach promises up to 30 percent extra bandwidth.
Berthold favours using channel ‘quanta’ rather than adopting a fully flexibility band scheme - using a 37GHz window followed by a 17GHz window, for example - as the latter approach will likely reduce technology choice and lead to higher costs.
Wellbrock says coarse filtering would be needed using a gridless approach as capturing the complete C-Band would be too noisy. A band 5 or 6 channels wide would be grabbed and the signal of interest recovered by tuning to the desired spectrum using a coherent receiver’s tunable laser, similar to how a radio receiver works.
Wellbrock says considerable technical progress is needed for the scheme to achieve a reach of 1500km or greater.
“Whatever the solution is it will have to be cheap”
Joe Berthold, Ciena.
JDS Uniphase’s Collings sounds a cautionary note about going gridless. “50GHz is nailed down – the number of questions asked that need to be addressed once you go gridless balloons,” he says. “This is very complex; we need to keep a very close eye that we are not creating more problems than we are solving.”
“Operators such as AT&T and Verizon have invested heavily in 50GHz ROADMs, they are not just going to ditch them,” adds Chris Clarke, vice president strategy and chief engineer at Oclaro.
More powerful FEC schemes and in particular soft-decision FEC (SD-FEC) will also benefit optical performance for data rates above 100Gbps. SD-FEC delivers up to a 1.3dB coding gain improvement compared to traditional FEC schemes at 100Gbps.
SD-FEC also paves the way for performing joint iterative FEC decoding and signal equalisation at the coherent receiver, promising further performance improvements, albeit at the expense of a more complex digital signal processor design.
400Gbps or 1 Tbps?
Even the question of what the next data rate after 100Gbps will be –200Gbps, 400Gbps or even 1 Terabit-per -second – remains unresolved.
Verizon Business will deploy new 100Gbps coherent-optimised routes from 2011 and would like as much clarity as possible so that such routes are future-proofed. But Collings points out that this is not something that will stop a carrier addressing immediate requirements. “Do they make hard choices that will give something up today?” he says.
At the OFC Executive Forum, Verizon Business expressed a preference for 1Tbps lightpaths. While 400Gbps was a safe bet, going to 1Tbps would enable skipping one additional stage i.e. 400Gbps. But Verizon recognises that backing 1Tbps depends on when such technology would be available and at what cost.
According to BT, speeds such as 200, 400Gbps and even 1 Tbps are all being considered. “The 200/ 400Gbps systems may happen using multiple QAM modulation,” says Russell Davey, core transport Layer 1 design manager at BT. “Some work is already being done at 1Tbps per wavelength although an alternative might be groups or bands of wavelengths carrying a continuous 1Tbps channel, such as ten 100Gbps wavelengths or five 200Gbps wavelengths.”
Davey stresses that the industry shouldn’t assume that bit rates will continue to climb. Multiple wavelengths at lower bitrates or even multiple fibres for short distances will continue to have a role. “We see it as a mixed economy – the different technologies likely to have a role in different parts of network,” says Davey.
Niall Robinson, vice president of product marketing at Mintera, is confident that 400Gbps will be the chosen rate.
Traditionally Ethernet has grown at 10x rates while SONET/SDH has grown in four-fold increments. However now that Ethernet is a line side technology there is no reason to expect the continued faster growth rate, he says. “Every five years the line rate has increased four-fold; it has been that way for a long time,” says Robinson. “100Gbps will start in 2012/ 2013 and 400Gbps in 2017.”
“There is a lot of momentum for 400Gbps but we’ll have a better idea in a six months’ time,” says Matt Traverso, senior manager, technical marketing at Opnext. “The IEEE [and its choice for the next Gigabit Ethernet speed after 100GbE] will be the final arbiter.”
Software defined optics and cognitive optics
Optical transmission could ultimately borrow two concepts already being embraced by the wireless world: software defined radio (SDR) and cognitive radio.
SDR refers to how a system can be reconfigured in software to implement the most suitable radio protocol. In optical it would mean making the transmitter and receiver software-programmable so that various transmission schemes, data rates and wavelength ranges could be used. “You would set up the optical transmitter and receiver to make best use of the available bandwidth,” says ADVA Optical Networking’s Elbers.
This is an idea also highlighted by Nokia Siemens Networks, trading capacity with reach based on modifying the amount of information placed on a carrier.
“For a certain frequency you can put either one bit [of information] or several,” says Oliver Jahreis, head of product line management, DWDM at Nokia Siemens Networks. “If you want more capacity you put more information on a frequency but at a lower signal-to-noise ratio and you can’t go as far.”
Using ‘cognitive optics’, the approach would be chosen by the optical system itself using the best transmission scheme dependent capacity, distance and performance constraints as well as the other lightpaths on the fibre. “You would get rid of fixed wavelengths and bit rates altogether,” says Elbers.
Market realities
Ovum’s view is it remains too early to call the next rate following 100Gbps.
Other analysts agree. “Gridless is interesting stuff but from a commercial standpoint it is not relevant at this time,” says Andrew Schmitt, directing analyst, optical at Infonetics Research.
Given that market research firms look five years ahead and the next speed hike is only expected from 2017, such a stance is understandable.
Optical module makers highlight the huge amount of work still to be done. There is also a concern that the benefits of corralling the industry around coherent DP-QPSK at 100Gbps to avoid the mistakes made at 40Gbps will be undone with any future data rate due to the choice of options available.
Even if the industry were to align on a common option, developing the technology at the right price point will be highly challenging.
“Many people in the early days of 100Gbps – in 2007 – said: ‘We need 100Gbps now – if I had it I’d buy it’,” says Rafik Ward, vice president of marketing at Finisar. “There should be a lot of pent up demand [now].” The reason why there isn’t is that such end users always miss out key wording at the end, says Ward: “If I had it I’d buy it - at the right price.”
For Part 1, click here
For Part 2, click here
Is a datacom and telecom mini-boom taking place?
Daryl Inniss believes it is largely a reflection of cutbacks that have run their course. “The industry cut back swiftly and deeply when the market started to tank, cutting suppliers and capacity,” says Inniss, practice leader, components at market research firm Ovum.
“I think it's recovery dynamics - people ordering a tiny bit more and there are no parts available such that lead-times are stretching out simulating a boom.”
Brad Smith, LightCounting
Carriers supported the demand with inventory. “Now the industry needs to support both deployments and inventory and with the traffic continuing to grow suppliers cannot meet demand,” he says. Moreover this “bull-whip effect” impacts most severely suppliers furthest removed from the carriers i.e. component vendors.
Brad Smith, senior vice president at optical transceiver market research firm LightCounting, also explains the situation based on events last year.
“There is a shortage of certain parts in optical and semis as a result of cutbacks in manufacturing during 2009,” says Smith, “I think it's recovery dynamics - people ordering a tiny bit more and there are no parts available such that lead-times are stretching out simulating a boom.”
Late last year a research note highlighted industry reports that shortages were becoming more widespread, including components such as integrated circuits and fiber optic transceivers.
However one leading optical transceiver vendor commented that it is shipping everything it can make and that it can’t build stuff fast enough.
So is there a mini-boom after all?
40 and 100Gbps: Growth assured yet uncertainty remains
Part 2: 40 and 100Gbps optical transmission
The market for 40 and 100 Gigabit-per-second optical transmission is set to grow over the next five years at a rate unmatched by any other optical networking segment. Such growth may excite the industry but vendors have tough decisions to make as to how best to pursue the opportunity.
Market research firm Ovum forecasts that the wide area network (WAN) dense wavelength division multiplexing (DWDM) market for 40 and 100 Gigabit-per-second (Gbps) linecards will have a 79% compound annual growth rate (CAGR) till 2014.
In turn, 40 and 100Gbps transponder volumes will grow even faster, at 100% CAGR till 2015, while revenues from 40 and 100Gbps transponder sale will have a 65% CAGR during the same period.
Yet with such rude growth comes uncertainty.
“We upgraded to 40Gbps because we believe – we are certain, in fact – that across the router and backbone it [40Gbps technology] is cheaper.”
Jim King, AT&T Labs
Systems, transponder and component vendors all have to decide what next-generation modulation schemes to pursue for 40Gbps to complement the now established differential phase-shift keying (DPSK). There are also questions regarding the cost of the different modulation options, while vendors must assess what impact 100Gbps will have on the 40Gbps market and when the 100Gbps market will take off.
“What is clear to us is how muddled the picture is,” says Matt Traverso, senior manager, technical marketing at Opnext.
Economics
Despite two weak quarters in the second half of 2009, the 40Gbps market continues to grow.
One explanation for the slowdown was that AT&T, a dominant deployer of 40Gbps, had completed the upgrade of its IP backbone network.
Andreas Umbach, CEO of u2t Photonics, argues that the slowdown is part of an annual cycle that the company also experienced in 2008: strong 40Gbps sales in the first half followed by a weaker second half. “In the first quarter of 2010 it seems to be repeating with the market heating up,” says Umbach.
This is also the view of Simon Warren, Oclaro’s director product line managenent, transmission product line. “We are seeing US metro demand coming,” he says. “And it is very similar with European long-haul.”
BT, still to deploy 40Gbps, sees the economics of higher-speed transmission shifting in the operator’s favour. “The 40Gbps wavelengths on WDM transmission systems have just started to cost in for us and we are likely to start using it in the near future,” says Russell Davey, core transport Layer 1 design manager at BT.
What dictates an operator upgrade from 10Gbps to 40Gbps, and now also to 100Gbps, is economics.
The transition from 2.5Gbps to 10Gbps lightpaths that began in 1999 occurred when 10Gbps approached 2.5x the cost of 2.5Gbps. This rule-of-thumb has always been assumed to apply to 40Gbps yet thousands of wavelengths have been deployed while 40Gbps remains more than 4x the cost of 10Gbps. Now the latest rule-of-thumb for 100Gbps is that operators will make the transition once 100Gbps reaches 2x 40Gbps i.e. gaining 25% extra bandwidth for free.
The economics is further complicated by the continuing price decline of 10Gbps. “Our biggest competitor is 10Gbps,” says Niall Robinson, vice president of product marketing at 40Gbps module maker Mintera.
“The traditional multiplier of 2.5x for the transition to 10Gbps is completely irrelevant for the 10 to 40 Gigabit and 10 to 100 Gigabit transitions,” says Andrew Schmitt, directing analyst of optical at Infonetics Research. “The transition point is at a higher level; even higher than cost-per-bit parity.”
So far two classes of operators adopting 40Gbps have emerged: AT&T, China Telecom and cable operator Comcast which have made, or plan, significant network upgrades to 40Gbps, and those such as Verizon Business and Qwest that have used 40Gbps more strategically for selective routes. For Schmitt there is no difference between the two: “These are economic decisions.”
AT&T is in no doubt about the cost benefits of moving to higher speed transmission. “We upgraded to 40Gbps because we believe – we are certain, in fact – that across the router and backbone it [40Gbps technology] is cheaper,” says Jim King, executive director of new technology product development and engineering, AT&T Labs.
King stresses that 40Gbps is cheaper than 10Gbps in terms of capital expenditure and operational expense. IP efficiencies result and there are fewer larger pipes to manage whereas at lower rates “multiple WDM in parallel” are required, he says.
“We see 100Gbps wavelengths on transmission systems available within a year or so, but we think the cost may be prohibitive for a while yet, especially given we are seeing large reductions in 10Gbps,” says Davey. BT is designing the line-side of new WDM systems to be compatible with 40Gbps – and later 100Gbps - even though it will not always use the faster line-cards immediately.
Even when an operator has ample fibre, the case for adopting 40Gbps on existing routes is compelling. That’s because lighting up new fibre is “enormous costly”, says Joe Berthold, Ciena’s vice president of network architecture. By adding 40Gbps to existing 10Gbps lightpaths at 50GHz channel spacing, capacity on an existing link is boosted and the cost of lighting up a separate fibre is forestalled.
According to Berthold, lighting a new fibre costs about the same as 80 dense DWDM channels at 10Gbps. “The fibre may be free but there is the cost of the amplifiers and all the WDM terminals,” he says. “If you have filled up a line and have plenty of fibre, the 81st channel costs you as much as 80 channels.”
The same consideration applies to metropolitan (metro) networks when a fibre with 40, 10Gbps channels is close to being filled. “The 41st channel also means six ROADMs (reconfigurable optical add/drop multiplexers) and amps which are not cheap compared to [40Gbps] transceivers,” says Berthold.
Alcatel-Lucent segments 40Gbps transmission into two categories: multiplexing of lower speed signals into a higher speed 40Gbps line-side trunk link - ‘muxing to trunk’ - and native 40Gbps transmission where the client-side, signal is at 40Gbps.
“The economics of the two are somewhat different,” says Sam Bucci, vice president, optical portfolio management at Alcatel-Lucent. The economics favour moving to higher capacity trunks. That said, Alcatel-Lucent is seeing native 40Gbps interfaces coming down in price and believes 100GbE interfaces will be ‘quite economical’ compared to 10x10Gbps in the next two years.
Further evidence regarding the relative expense of router interfaces is given by Jörg-Peter Elbers, vice president, advanced technology at ADVA Optical Networking, who cites that in overall numbers currently only 20% go into 40Gbps router interfaces while the remaining 80% go into muxponders.
Modulation Technologies
While economics dictate when the transition to the next-generation transmission speed occurs, what is complicating matters is the wide choice of modulation schemes. Four modulation technologies are now being used at 40Gbps with operators having the additional option of going to 100Gbps.
The 40Gbps market has already experienced one false start back in 2002/03. The market kicked off in 2005, at least that is when the first 40Gbps core router interfaces from Cisco Systems and Juniper Networks were launched.
"There is an inability for guys like us to do what we do best: take an existing interface and shedding cost by driving volumes and driving the economics.”
Rafik Ward, Finisar
Since then four 40Gbps modulation schemes are now shipping: optical duobinary, DPSK, differential quadrature phase-shift keying (DQPSK) and polarisation multiplexing quadrature phase-shift keying (PM-QPSK). PM-QPSK is also referred to as dual-polarisation QPSK or DP-QPSK.
“40Gbps is actually a real mess,” says Rafik Ward, vice president of marketing at Finisar.
The lack of standardisation can be viewed as a positive in that it promotes system vendor differentiation but with so many modulation formats available the lack of consensus has resulted in market confusion, says Ward: “There is an inability for guys like us to do what we do best: take an existing interface and shedding cost by driving volumes and driving the economics.”
DPSK is the dominant modulation scheme deployed on line cards and as transponders. DPSK uses relatively simple transmitter and receiver circuitry although the electronics must operate at 40Gbps. DPSK also has to be modified to cope with tighter 50GHz channel spacing.
“DPSK’s advantage is relatively simple,” says Loi Nguyen, founder, vice president of networking, communications, and multi-markets at Inphi. “For 1200km it works fine, the drawback is it requires good fibre.”
The DQPSK and DP-QPSK modulation formats being pursued at 40Gbps offer greater transmission performance but are less mature.
DQPSK has a greater tolerance to polarisation mode dispersion (PMD) and is more resilient when passing through cascaded 50GHz channels compared to DPSK. However DQPSK uses more complex transmitter and receiver circuitry though it operates at half the symbol rate – at 20Gbaud/s - simplifying the electronics.
DP-QPSK is even more complex than DQPSK requiring twice as much optical circuitry due to the use of polarisation multiplexing. But this halves again the symbol rate to 10Gbaud/s, simplifying the design constraints of the optics. However DP-QPSK also requires a complex application-specific integrated circuit (ASIC) to recover signals in the presence of such fibre-induced signal impairments as chromatic dispersion and PMD.
The ASIC comprises high-speed analogue-to-digital converters (ADCs) that sample the real and imaginary components that are the output of the DP-QPSK optical receiver circuitry, and a digital signal processor (DSP) which performs the algorithms to recovery the original transmitted bit stream in the presence of dispersion.
The chip is costly to develop – up to US $20 million – but its use reduces line costs by allowing fewer optical amplifiers numbers and removing PMD and chromatic dispersion in-line compensators.
“You can build more modular amplifiers and really optimise performance/ cost,” says Bucci. Such benefits only apply when a new optimised route is deployed, not when 40Gbps lightpaths are added to existing fibre carrying 10Gbps lightpaths.
Eliminating dispersion compensation fibre in the network using coherent detection brings another important advantage, says Oliver Jahreis, head of product line management, DWDM at Nokia Siemens Networks. “It reduces [network] latency by 10 to 20 percent,” he says. “This can make a huge difference for financial transactions and for the stock exchange.”
Because of the more complex phase modulation used, 40Gbps DQPSK and DP-QPSK lightpaths when lit alongside 10Gbps suffer from crosstalk interference. “DQPSK is more susceptible to crosstalk but coherent detection is even worse,” says Chris Clarke, vice president strategy and chief engineer at Oclaro.
Wavelength management - using a guard-band channel or two between the 10Gbps and 40Gbps lightpaths – solves the problem. Alcatel-Lucent also claims it has developed a coherent implementation that works alongside existing 10Gbps and 40Gbps DPSK signals without requiring such wavelength management.
100Gbps consensus
Because of the variety of modulation schemes at 40Gbps the industry has sought to achieve a consensus at 100Gbps resulting in coherent becoming the defacto standard.
Early-adopter operators of 40Gbps technology such as AT&T and Verizon Business have been particularly vocal in getting the industry to back DP-QPSK for 100Gbps. The Optical Internetworking Forum (OIF) industry body has also done much work to provide guidelines for the industry as part of its 100Gbps Framework Document.
Yet despite the industry consensus, DP-QPSK will not be the sole modulation scheme targeted at 100Gbps.
ADVA Optical Networking is pursuing 100Gbps technology for the metro and enterprise using a proprietary modulation scheme. “If you look at 100Gbps, we believe there is room for different solutions,” says Elbers.
For metro and enterprise systems, the need is for more compact, less power-consuming, cheaper solutions. ADVA Optical Networking is following a proprietary approach. At ECOC 2008 the company published a paper that combined DPSK with amplitude-shift keying.
“If you look at 100Gbps, we believe there is room for different solutions.”
Jörg-Peter Elbers, ADVA Optical Networking
“Coherent DP-QPSK offers the highest performance but it is not required for certain situations as it brings power and cost burdens,” says Elbers. The company plans to release a dedicated product for the metro and enterprise markets and Elbers says the price point will be very close to 10x10Gbps.
Another approach is that of Australian start-up Ofidium. It is using a multi-carrier modulation scheme based on orthogonal frequency-division multiplexing. Ofidium claims that while OFDM is an alternative modulation scheme to DP-QPSK, it uses the same optical building blocks as recommended by the OIF.
Decisions, decisions
Simply looking at the decisions of a small sample of operators highlights the complex considerations involved when deciding a high-speed optical transmission strategy.
Cost is clearly key but is complicated by the various 40Gbps schemes being at different stages of maturity. 40Gbps DPSK is deployed in volume and is now being joined by DQPSK. Coherent technology was, until recently, provided solely by Nortel, now owned by Ciena. However, Nokia Siemens Networks working with CoreOptics, and Fujitsu have recently announced 40Gbps coherent offerings upping the competition.
Ciena also has a first-generation 100Gbps technology and will soon be joined by system vendors either developing their own 100Gbps interfaces or are planning to offer 100Gbps once DP-QPSK transponders become available in 2011.
The particular performance requirements also influence the operators’ choices.
Verizon Business has limited its deployment of DPSK due to the modulation scheme’s tolerance to PMD. “It is quite low, in the 2 to 4 picosecond range,” says Glenn Wellbrock, director of backbone network design at Verizon Business. “We have avoided deploying DPSK even if we have measured the [fibre] route [for PMD].”
Because PMD can degrade over time, even if a route is measured and is within the PMD tolerance there is no guarantee the performance will last. Verizon will deploy DQPSK this year for certain routes due to its higher 8ps tolerance to PMD.
China Telecom is a key proponent of DQPSK for its network rollout of 40Gbps. “It has doubled demand for its 40Gbps build-out and the whole industry is scrambling to keep up,” says Oclaro’s Clarke.
AT&T has deployed DPSK to upgrade its network backbone and will continue as it upgrades its metro and regional networks. “Our stuff [DPSK transponders] is going into [these networks],” says Mintera’s Robinson. But AT&T will use other technologies too.
In general modulation formats are a vendor decision, “something internal to the box”, says King. What is important is their characteristics and how the physics and economics match AT&T’s networks. “As coherent becomes available at 40Gbps, we will be able to offer it where the fibre characteristics require it,” says King.
“AT&T is really hot on DP-QPSK,” says Ron Kline, principal analyst of network infrastructure at Ovum. “They have a whole lot of fibre - stuff before 1998 - that is only good for 2.5Gbps and maybe 10Gbps. They have to be able to use it as it is hard to replace.”
BT points out how having DP-QPSK as the de facto standard for 100Gbps will help make it cost-effective compared to 10Gbps and will also benefit 40Gbps coherent designs. “This offers high performance 40Gbps which will probably work over all of our network,” says Davey.
But this raises another issue regarding coherent: it offers superior performance over long distances yet not all networks need such performance. “For the UK it may be that we simply don’t have sufficient long distance links [to merit DP-QPSK] and so we may as well stick with non-coherent,” says Davey. “In the end pricing and optical reach will determine what is used and where.”
One class of network where reach is supremely important is submarine.
For submarine transmission, reaches between 5,000 and 7,000km can be required and as such 10Gbps links dominate. “In the last six months even if most RFQs (Request for Quotation from operators) are about 10Gbps, all are asking about the possibility of 40Gbps,” says Jose Chesnoy, technical director, submarine network activity at Alcatel-Lucent.
Until now there has also been no capacity improvement in submarine adopting 40Gbps: 10Gbps lightpaths use 25GHz-spaced channels while 40Gbps uses 100GHz. “Now with technology giving 40Gbps performance at 50GHz, fibre capacity is doubled,” says Chesnoy.
To meet trans-ocean distances for 40Gbps submarine, Alcatel-Lucent is backing coherent technology, as it is for terrestrial networks. “Our technology direction is definitely coherent, at 40 and 100Gbps,” says Bucci.
Ciena, with its acquisition of Nortel’s Metro Ethernet Networks division, now offers 40 and 100Gbps coherent technology.
“It’s like asking what the horsepower per cylinder is rather than the horsepower of the engine.”
Drew Perkins, Infinera
ADVA Optical Networking, unlike Ciena and Alcatel-Lucent, is not developing 40Gbps technology in-house. “When looking at second generation 40Gbps, DQPSK and DP-QPSK are both viable options from a performance point of view,” says Elbers.
He points out that what will determine what ADVA Optical Networking adopts is cost. DQPSK has a higher nonlinear tolerance and can offer lower cost compared to DP-QPSK but there are additional costs besides just the transponder for DQPSK, he says, namely the need for an optical pre-amplifier and an optical tunable dispersion compensator per wavelength.
DP-QPSK, for Elbers, eliminates the need for any optical dispersion compensation and complements 100Gbps DP-QPSK, but is currently a premium technology. “If 40Gbps DP-QPSK is close to the cost of 4x10Gbps tunable XFP [transceivers], it will definitely be used,” he says. “We are not seeing that yet.”
Infinera, with its photonic integrated circuit (PIC) technology, questions the whole premise of debating 40Gbps and 100Gbps technologies. Infinera believes what ultimately matters is how much capacity can be transmitted over a fibre.
“Most people want pure capacity,” says Drew Perkins, Infinera’s CTO, who highlights the limitations of the industry’s focus on line speed rather than overall capacity using the analogy of buying a car. “It’s like asking what the horsepower per cylinder is rather than the horsepower of the engine,” he says.
Infinera offers a 10x10Gbps PIC though it has still not launched its 10x40Gbps DP-DQPSK PIC. “The components have been delivered to the [Infinera] systems group,” says Perkins. The former CEO of Infinera, Jagdeep Singh, has said that while the company is not first to market with 40Gbps it intends to lead the market with the most economical offering.
Moreover, Infinera is planning to develop its own coherent based PIC. “The coherent approach - DP-QPSK ‘Version 1.0’ with a DSP - is very powerful with its high capacity and long reach but it has a significant power density cost,” says Perkins. “We envisage the day when there will be a 10-channel PIC with a 100Gbps coherent-type technology in 50GHz spectrum at very low power.” Such PIC technology would deliver 8 Terabits over a fibre.
Further evidence of the importance of 100Gbps is given by Verizon Business which has announced that it will deploy 100Gbps coherent-optimized fibre links starting next year that will do away with dispersion compensation fibre. AT&T’s King says it will also deploy coherent-optimised links.
Not surprisingly, views also differ among module makers regarding the best 40Gbps modulation schemes to pursue.
“We had a very good look at DQPSK,” says Mintera’s Robinson. “What’s best to invest? The price comparison [DQPSK versus coherent] is very similar yet DP-QPSK is vastly superior [in performance]. Put in a module it will kill off DP-QPSK.”
Finisar has yet to detail its plans but Ward says that the view inside the company is that the lowest cost interface is offered by DPSK while DP-QPSK delivers high performance. “DQPSK is in this challenging position, it can’t meet the cost point of DPSK nor the performance of DP-QPSK,” he says.
Opnext begs to differ.
The firm offers the full spectrum of 40Gbps modulation schemes - optical duobinary, DPSK and DQPSK. “The next phase we are focussed on is 100Gbps coherent,” says Traverso. “We are not as convinced that 40Gbps is a sweet spot.”
In contrast Opnext does believe DQPSK will be popular, although Traverso highlights that it depends on the particular markets being addressed, with DQPSK being particularly suited to regional networks. “One huge advantage of DQPSK is thermal – the coherent IC burns a lot of power”.
Oclaro is also backing DQPSK as the format for metro and regional networks: fibre is typically older and the number of ROADM stages a signal encounters is higher.
Challenges
The maturity of the high–speed transmission supply chain is one challenge facing the industry.
“Many of the critical components are not mature,” says Finisar’s Ward. “There are a lot of small companies - almost start-ups - that are pioneers and are doing amazing things but they are not mature companies.”
JDS Uniphase believes that with the expected growth for 40Gbps and 100Gbps there is an opportunity for the larger optical vendors to play a role. “The economic and technical challenges are still a challenge,” says Tom Fawcett, JDS Uniphase’s director of product line management.
Driving down cost at 40Gbps remains a continuing challenge, agrees Nguyen: “Cost is still an important factor; operators really want lower cost”. To address this the industry is moving along the normal technology evolution path, he says, reducing costs, making designs more compact and enabling the use of techniques such as surface-mount technology.
Mintera has developed a smaller 300-pin MSA DPSK transponder that enable two 40Gbps interfaces on one card: the line side and client side ones. Shown on the right is a traditional 5"x7" 300-pin MSA.
JDS Uniphase’s strategy is to bring the benefits of vertical integration to 40 and 100Gbps; using its own internal components such as its integrated tunable laser assembly, lithium niobate modulator, and know-how to produce an integrated optical receiver to reduce costs and overall power consumption.
Vertical integration is also Oclaro’s strategy with is 40Gbps DQPSK transponder that uses its own tunable laser and integrated indium-phosphide-based transmitter and receiver circuitry.
“[Greater] vertical integration will make our lives more difficult,” says u2t’s Umbach. “But any module maker that has in-house components will only use them if they have the right optical performance.”
Jens Fiedler, vice president sales and marketing at u2t Photonics,stresses that while DQPSK and DP-QPSK may reduce the speed of the photodetectors and hence appear to simplify design requirements, producing integrated balanced receivers is far from trivial. And by supplying multiple customers such as non-vertically integrated module makers and system vendors, merchant firms also have a volume manufacturing advantage.
Opnext has already gone down the vertically integrated path with its portfolio of 40Gbps offerings and is now developing an ASIC for use in its 100Gbps transponders.
Estimates vary that there are between eight and ten companies or partnerships developing their own coherent ASIC. That equates to a total industry spend of some $160 million, leading some to question whether the industry as a whole is being shrewd with its money. “Is that wise use of people’s money?” says Oclaro’s Clarke. “People have got to partner.”
The ASICs are also currently a bottleneck. “For 100Gbps the ASIC is holding everything up,” says Jimmy Yu, a director at the Dell'Oro Group
According to Stefan Rochus, vice president of marketing and business development at CyOptics, another supply challenge is the optical transmitter circuitry at 100Gbps while for 40Gbps DP-QPSK, the main current supplier is Oclaro.
“The [40Gbps] receiver side is well covered,” says Rochus.
CyOptics itself is developing an integrated 40Gbps DPSK balanced receiver that includes a delay-line inteferometer and a balanced receiver. The firm is also developing a 40 and a 100G PM-QPSK receiver, compliant with the OIF Framework Document. This is also a planar lightwave circuit-based design but what is different between 40 and 100Gbps designs is the phodetectors - 10 and 28GHz respectively - and the trans-impedence amplifiers (TIAs).
NeoPhotonics is another optical component company that has announced such integrated DM-QPSK receivers.
And u²t Photonics recently announced a 40G DQPSK dual balanced receiver that it claims reduces board space by 70%, and it has also announced with Picometrix a 100Gbps coherent receiver multi-source agreement.
40 and 100Gbps: next market steps
Verizon Business in late 2009 became the first operator to deploy a 100Gbps route linking Frankfurt and Paris. And the expectation is that only a few more 100Gbps lightpaths will be deployed this year.
The next significant development is the ratification of the 40 and 100 Gigabit Ethernet standards that will happen this year. The advent of such interfaces will spur 40Gbps and 100Gbps line side. After that 100Gbps transponders are expected in mid-2011.
Such transponders will have a two-fold effect: they will enable more system vendors to come to market and reduce the cost of 100Gbps line-side interfaces.
However industry analysts expect the 100Gbps volumes to ramp from 2013 onwards only.
Dell'Oro’s Yu expects the 40Gbps market to grow fiercely all the while 100Gbps technology matures. At 40Gbps he expects DPSK to continue to ship. DP-QPSK will be used for long haul links - greater than 1200km –while DQPSK will find use in the metro. “There is room for all three modulations,” says Yu.
|
40 100G market |
Compound annual growth rate CAGR |
|
Line card volumes |
79% till 2014 |
|
Transponder volumes |
100% till 2015 |
|
Transponder revenues |
65% till 2015 |
Source: Ovum
Ovum and Infonetics have different views regarding the 40Gbps market.
“Coherent is the story; the opportunity for DQPSK being limited,” says Ovum’s Kline. Infonetics’ Schmitt disagrees: “If you were to look back in 2015 over the last five years, the bulk of the deployments [at 40Gbps] will be DQPSK.
Schmitt does agree that 2013 will be a big year for 100Gbps: “100Gbps will ramp faster than 40Gbps but it will not kill it.”
Schmitt foresees operators bundling 10Gbps wavelengths into both 40Gbps and 100Gbps lightpaths (and 10Gbps and 40Gbps lightpaths into 100Gbps ones) using Optical Transport Networking (OTN) encapsulation technology.
Given the timescales, vendors still to make their 40Gbps modulation bets run the risk of being late to market. They are also guaranteed a steep learning curve. Yet those that have made their decisions at 40Gbps will likely remain uncomfortable for a while yet until they can better judge the wisdom of their choices.
For the first part of this feature, click here
For Part 3, click here
DSL: Will phantom channels become real deployments?
Alcatel-Lucent is promoting its DSL Phantom Mode technology as a complement to fibre-to-the-x (FTTx) technology. Operators can use the technology to continue to extend services offerings to existing DSL subscribers as they roll out FTTx over the next decade or more.
But one analyst believes the technology could take years to commercialise and questions whether the announcement is not sending a wrong message to the industry by providing an alternative to fibre.
“The investment required to upgrade DSL is quite small”
Stefaan Vanhastel, Alcatel-Lucent
What has been achieved?
The 300Mbps data rate is achieved using two copper wire pairs between the access equipment and a DSL modem although three DSL ports are required at each end. The rate drops to 100Mbps when the reach is extended to 1km. In comparison very high speed Digital Subscriber Line 2’s (VDSL2) data rate over a single line ranges from 20 to 40Mbps over 1km.
None of the three techniques that Alcatel-Lucent uses – bonding, vectoring and the phantom mode that creates an extra virtual channel alongside the two bonded pairs - is new. What the company claims is that it is the first to combine all three for DSL.
In March Ericsson announced it had achieved 500Mbps over 500m but it used six bonded pairs and vectoring only.
Why is the Phantom Mode important?
The significance of the announcement, according to Alcatel-Lucent, is that operators can continue to offer existing DSL customers new bandwidth-intensive services as they roll out FTTx.
“Rolling out FTTx will take a significant amount of time,” says Stefaan Vanhastel, director of product marketing, wireline networks at Alcatel-Lucent. “Operators are looking to reuse their copper infrastructure in the short-to-medium term - the next 5 to 10 years.”
An operator must have a central office or cabinet equipment 1km or less from the user’s residence as well as having two wire pairs per building or residence. “In many countries two pairs are available,” says Vanhastel.
However, one analyst questions the development and promotion of such copper-enhancing technology.
“I think Alcatel is being disingenuous when they say "fiber will take long to implement, this is an intermediary solution’,” says the analyst, who asked not to be named. “They know full well that customers would see this as a way to hold back on deploying fibre.
“Ultimately to me this is schizophrenia at work. Alcatel-Lucent wants to be all things to all service providers and may be sending the wrong message to the market that they need not invest to sustain the bandwidth demand growth, which is suicidal both for service providers and for Alcatel-Lucent in the long run.”
Alcatel-Lucent does believe operators will invest in DSL alongside FTTx.
“The investment required to upgrade DSL is quite small,” says Vanhastel. “Even with two ports it is a bargain; you get the investment back in one or two months.”
Even operators more advanced in their FTTx deployments will want to offer new higher bandwidth services such as high-definition TV to all their customers.
“What are you going to do? Offer your services to just 50% of your customers?” says Vanhastel “They [the remaining customers] will go elsewhere.”
Method used
The Bell Labs research arm of Alcatel-Lucent has used three techniques to enhance DSL’s speed and reach performance.
- Bonding: The combination of copper line pairs to boost the number of channels – in this case two are bonded - and hence the data rate between access equipment and the DSL modem.
- Vectoring: Noise cancellation techniques using digital signal processing to improve the overall signal-to-noise performance. “It involves measuring the noise on all the lines and generating anti-phase – the inverse signal – such that the two cancel out,” says Vanhastel.
- Phantom mode: The phantom mode technology uses two physical wires to create a third virtual one. The technology was first proposed in the 1880s as a way to add an extra virtual telephone line.
Two physical pairs and the third phantom one. Source: Alcatel-Lucent
Using the phantom mode, only two wire pairs are needed to connect the end equipment. The information on the third “virtual” line is shared over the two physical channels. Using analogue electronics, the data on the third channel is processed and recovered. “We add and subtract through the use of a bunch of transformers,” says Vanhastel. Where the circuitry is placed, whether in the DSLAM access equipment or elsewhere, is to be decided.
To create the virtual wire, a modem supporting three-pair bonding is required. In addition the chipset in the DSL modem must have sufficient processing performance to execute vectoring on three channels. That's because adding the phantom mode degrades the performance of all the channels due to crosstalk. The crosstalk is removed between the channels using vectoring.
What next?
The technology needs to be brought to market. “At the earliest it will be 2012,” says Vanhastel.
But the analyst points out that the technology is lab tested: “Between test labs and implementation, count a significant number of years.”
The concept could even be extended using more wire pairs. The relationship is (N-1) phantom channels for N wire pairs i.e. 1 virtual channel with two pairs, 2 with 3 pairs etc.
Alcatel-Lucent says it has already completed two VDSL2 bonding trials in Asia Pacific, while three operators are undertaking VDSL2 vectoring tests in their labs and will move to testing in the field using a single line this year.
“Bonding is here today, vectoring will be 2011 and the phantom mode will be after that,” says Vanhastel.
OFC/NFOEC 2010: Industry reflections
Here is a selection of their views.
“We heard again and again, that the internet service providers such as Google are still looking for solutions for their future bandwidth demand”
Andreas Umbach, u2t Photonics
OFC highlights
For many the story of the show was 40Gbps and 100Gbps long-haul transport.
“Of the many announcements I thought Opnext’s component technology and product announcements were notable as a big bet on bleeding-edge R&D by an established components player,” says Scott Schube, senior analyst and strategist at market research firm, LightCounting.
The developments Schube highlights include Opnext’s 100Gbps SerDes, 100Gbps DSP for coherent receivers, and various optical modules for 100Gbps, along with its field trial with AT&T announced before the show.
Andreas Umbach, CEO of u2t Photonics, notes the industry acceptance of dual-polarisation QPSK as the standard for 100Gbps. Oclaro also highlights the Optical Internetworking Forum’s (OIF) work towards a single solution, to avoid the proliferation of solutions that occurred at 40Gbps. “Most view this as a good sign, but it does remove some of the flexibility to introduce new innovations,” says Chris Clarke, vice president strategy and chief engineer at Oclaro.
OFC/NFOEC 2010 also marked the return of the system vendors, according to Karen Liu, vice president, components and video technologies at market research firm Ovum.
“There were two big trailers on the floor from Huawei and Ciena-Nortel. Each was a complete demo room showing multiple systems interoperating,” she says. “Ciena-Nortel with Corning had a demo involving 3000km of fibre.”
But others disagree. “The box makers have really pulled back at this show compared to those in the past,” says Neal Neslusan, a consultant at PhiBos Consulting. “With Supercomm now finally dead it makes one wonder what is the target show for the telecom box makers.”
“The biggest thing was the general sense that bandwidth on the fibre is no longer plentiful”
Karen Liu, Ovum
One datacom demonstration highlighted by LightCounting was Avago’s microPOD 120Gbps parallel optical modules shown as part of an IBM supercomputing blade. “Reflex Photonics and others have showed similar technology before, but Avago’s announcement shows that we might be getting close to true commercialization of “optics on board” products,” said Schube.
Liu was also taken by IBM’s water-cooled processor board with the Avago optical interconnect based on a novel connector made by injection-molded high-precision lensing: “There were 28 modules, 120Gbps each, on the board.”
What else besides 40 and 100Gbps?
Passive Optical Networks (PON) received huge attention, says David Menashe, vice president and chief scientist at RED-C Optical Networks. “There is a lot of activity around next-generation PON architectures including higher rates and longer reach, merging of access and metro networks and reducing the number of central offices,” he says
LightCounting highlights continuing innovation at 10Gbps which, it says, still has years of market dominance ahead of it. Schube notes the demos from several IC vendors of smaller, lower power, more integrated 10G PHYs and framers, as well as two companies introduced long-reach SFP+ modules, and Finisar’s demonstration of a new tunable XFP module.
“The tunable XFP seemed to gain general market acceptance with several suppliers announcing upcoming releases,” says Sinclair Vass, senior EMEA director at JDS Uniphase. He also noted a trend towards 1x23 type wavelength-selective switch (WSS) architectures with market agreement emerging as to what is required.
Learnt
For David Smith, CTO of CIP Technologies, the general acceptance of coherent detection as the solution for 100Gbps and beyond means that the two most important technologies driving the future of the industry will be photonic integration needed to realise the complex optics, and advances in electronic DSP technology to reap the flexibility and capacity.
“From the longer term research perspective orthogonal frequency-division multiplexing (OFDM) in its various guises increasingly seems to be the way people will see all this capability being harnessed,” he says
“40Gbps DPSK and DQPSK will live on and, in fact, grow very nicely,” says Neslusan. “I also learnt that at 40 and 100Gbps, the coherent detection offerings will not necessarily be adopted across the board; there is significant life for direct detection at both 40 and 100Gbps, specifically in the metro.”
“The most vocal component companies appear to have a long way to go to reign-in to a 100Gbps product; the claims seem to be significantly beyond the capability to commercialise in the near-term,” says Oclaro’s Clarke. “There is also a growing consensus that vertical integration will be increasingly valued going forward.”
“The biggest thing was the general sense that bandwidth on the fibre is no longer plentiful,” says Ovum’s Liu, highlighting how Cedric Lam of Google referred to it and Glenn Wellbrock from Verizon also made reference to it in the context of wanting a move to “gridless” - no longer being bound by the ITU’s rigid wavelengths used for DWDM - for high speed transmission.
Surprises
JDS Uniphase and RED-C stress that technology tends to move incrementally and as such did not see any ‘quantum leaps’. One interesting observation, according to JDS Uniphase, was the reduction in OFDM papers in 2010 compared to 2009. But it warns not to read too much into it: “Two points don’t make a trend,” the company said.
Eve Griliches, managing partner at ACG Research was surprised by how OFC was “overrun” by content providers: “A new breeze blowing in town was how it felt,” she says.
“It is noticeable that the direction for the industry is increasingly being set by web service companies such as Google and Facebook, says CIP’s Smith.“These people are now the drivers of the capacity demand and it is interesting that their requirements and vision does not quite align with that of the long haul operators that traditionally set the tone at OFC.”
Reasons for optimism?
“There was plenty,” says RED-C’s Menashe. 100Gbps and coherent detection has injected a lot of energy into the industry, he says. Combined with the expected growth in access networks, this should lead to healthy growth for several years.
LightCounting is encouraged that the industry is moving to more complex modulation and detection schemes despite the near- and even medium-term economic case for 100Gbps components is suspect, says Schube. Such developments define a technology roadmap for at least another decade of network capacity doubling every 18 months.
“We heard again and again, that the internet service providers such as Google are still looking for solutions for their future bandwidth demand,” says u2t’s Umbach.
“The component vendor landscape for 40G and 100G is turning out to be just like that at the beginning of 10G – that is to say, very overcrowded”
Scott Schube, LightCounting
JDS Uniphase argues that from the attendance of mainly larger stable suppliers it is clear that the ecosystem has fully evolved from the “excessive speculation by outside forces” which caused and broke the bubble. The current situation doesn’t mean that the industry is “a full picture of health or profitability”, it said, but predictability and stability may be returning.
For CIP, the show was as busy as previous OFCs but its serious leads were up by 30%. Interest was much more focussed on custom designs and volumes for solid commercial applications rather than one-off blue sky projects, it said.
“This year marked the en masse return of the "optical gadget" suppliers at OFC, specifically from China,” says Neslusan. “I consider this a good sign.”
Did you attend OFC? Is there something noteworthy that you'd like to highlight?