ECOC 2014: Industry reflections on the show
Gazettabyte asked several attendees at the recent ECOC show, held in Cannes, to comment on key developments and trends they noted, as well as the issues they will track in the coming year.
Daryl Inniss, practice leader, components at market research firm, Ovum
It took a while to unwrap what happened at ECOC 2014. There was no one defining event or moment that was the highlight of the conference.
The location was certainly beautiful and the weather lovely. Yet I felt the participants were engaged with critical technical and business issues, given how competitive the market has become.
Kaiam’s raising US $35 million, Ranovus raising $24 million, InnoLight Technology raising $38 million and being funded by Google Capital, and JDSU and Emcore each splitting into two companies, all are examples of the shifting industry structure.
On the technology and product development front, advances in 100 Gig metro coherent solutions were reported although products are coming to market later than first estimated. The client-side 100 Gig is transitioning to CFP2. Datacom participants agree that QSFP28 is the module but what goes inside will include both parallel single mode solutions and wavelength multiplexed ones.
Finisar’s 50 Gig transmission demonstration that used silicon photonics as the material choice surprised the market. Compared to last year, there were few multi-mode announcements. ECOC 2014 had little excitement and no one defining show event but there were many announcements showing the market’s direction.
There is one observation from the show, which while not particularly exciting or sexy, is important, and it seems to have gone unnoticed in my opinion. Source Photonics demonstrated the 100GBASE-LR4, the 10km 100 Gigabit Ethernet standard, in the QSFP28 form factor. This is not new as Source Photonics also demonstrated this module at OFC. What’s interesting is that no one else has duplicated this result.
There will be demand for a denser -LR4 solution that’s backward compatible with the CFP, CFP2, and CFP4 form factors. It is unlikely that the PSM4, CWDM4, or CLR4 will go 10km and they are not optically compatible with the -LR4. The market is on track to use the QSFP28 for all 100 Gig distances so it needs the supporting optics. The Source Photonics demonstration shows a path for 10km. We expect to see other solutions for longer distances over time.
One surprise at the show was Finisar's and STMicroelectronics's demonstration of 50 Gig non-return-to-zero transmission over 2.2km on standard single mode fiber. The transceiver was in the CFP4 form factor and uses heterogeneous silicon technologies inside. The results were presented in a post-deadline paper (PD.2.4). The work is exciting because it demonstrates a directly modulated laser operating above 28 Gig, the current state-of-the-art.
The use of silicon photonics is surprising because Finisar has been forced to defend its legacy technology against the threat of transceivers based on silicon photonics. These results point to one path forward for next-generation 100 Gig and 400 Gig solutions.
In the coming year, I’m looking for the dominant metro 100G solution to emerge. When will the CFP2 analogue coherent optical module become generally available? Multiple suppliers with this module will help unleash the 100 Gig line-side transmission market, drive revenue growth and the development for the next-generation solution.
Slow product development gives competing approaches like the digital CFP a chance to become the dominant solution. At present, there is one digital CFP vendor with a generally available product, Acacia Communications, with a second, Fujitsu Optical Components, having announced general availability in the first half of 2015.
Neal Neslusan, vice president of sales and marketing at fabless chip company, MultiPhy.
It was impressive to see Oclaro's analogue CFP2 for coherent applications on the show floor, albeit only in loopback mode. Equally impressive was seeing ClariPhy's DSP on the evaluation board behind the CFP2.
I saw a few of the motherboard-based optics solutions at the show. They looked very interesting and in questioning various folks in the business I learned that for certain data centre applications these optics are considered acceptable. Indeed, they represent an ability to extract much higher bandwidth from a given motherboard as compared to edge-of-the-board based optics, but they are not pluggable.
Traditionally, pluggable optics has been the mainstay of the datacom and enterprise segments and these motherboard-based optics have been relegated to supercomputing. This is just another example, in my opinion, of how the data centre market is becoming distinct from the datacom market.
Where there any surprises at the show? I was surprised and alarmed at the cost of the Martini drinks at the hotel across the street from the show, and they weren't even that good!
Regarding developments in the coming year, the 8x50 Gig versus 4x100 Gig fight in the IEEE is clearly a struggle I will follow. I think it will have a great impact on product development in our industry. If 8x50 Gig wins, it may be one of the few times in the history of our industry that a less advanced solution is chosen over a more advanced and future-proofed one.
The physical size of the next-generation Terabit Ethernet switch chips will have a much larger impact on the optics they connect to in the coming years, compared to the past. This work combined with the motherboard-based optics may create a significant change in the solutions brought to bear for high-performance communications.
John Lively, principal analyst at market research firm, LightCounting.
There were several developments that I noted at the show. ECOC helped cement the view that 100 Gig coherent is mainstream for metro networks. Also more and more system vendors are incorporating Raman/ remote optically pumped amplifier (ROPA) into their toolkit. ROPA is a Raman-based amplifier where the pump is located at one end of the link, not in some intermediate node. Another trend evident at ECOC is how the network boundary between terrestrial and submarine is blurring.
As for developments to watch, I intend to follow mobile fronthaul/ backhaul, higher speed transceiver developments, of course, and how the mega-data-centre operators are disrupting networks, equipment, and components.
For the ECOC reflections, final part, click here
Oclaro demonstrates flexible rate coherent pluggable module
- The CFP2 coherent optical module operates at 100 and 200 Gig
- Samples are already with customers, with general availability in the first half of 2015
- Oclaro to also make more CFP2 100GBASE-LR4 products
The CFP2 is not just used in metro/ regional networks but also in long-haul applications
Robert Blum
The advent of a pluggable CFP2, capable of multi-rate long-distance optical transmission, has moved a step closer with a demonstration by Oclaro. The optical transmission specialist showed a CFP2 transmitting data at 200 Gigabits-per-second.
The coherent analogue module demonstration, where the DSP-ASIC resides alongside rather than within the CFP2, took place at ECOC 2014 held in September at Cannes. Oclaro showcased the CFP2 to potential customers in March, at OFC 2014, but then the line side module supported 100 Gig only.
"What has been somewhat surprising to us is that the CFP2 is not just used in metro/ regional networks but also in long-haul applications," says Robert Blum, director of strategic marketing at Oclaro. "We are also seeing quite significant interest in data centre interconnect, where you want to get 400 Gig between sites using two CFP2s and two DSPs." Oclaro says that the typical distances are from 200km to 1,000km.
The CFP2 achieves 200 Gig using polarisation multiplexing, 16-quadrature amplitude modulation (PM-16-QAM) while working alongside ClariPhy's merchant DSP-ASIC. ClariPhy announced at ECOC that it is now shipping its 200 Gig LightSpeed-II CL20010 coherent system-on-chip, implemented using a 28nm CMOS process.
"One of the beauties of an analogue CFP2 is that it works with a variety of DSPs," says Blum. Other merchant coherent DSPs are becoming available, while leading long-haul optical equipment vendors have their own custom coherent DSPs.
Oclaro's CFP2, even when operating at 200 Gig, falls within the 12W module's power rating. "One of the things you need to have for 200 Gig is a linear modulator driver, and such drivers consume slightly more power [200mW] than limiting modulator drivers [used for 100 Gig only]," says Blum.
Oclaro will offer two CFP2 line-side variants, one with linear drivers and one using limiting ones. The limiting driver CFP2 will be used for 100 Gig only whereas the linear driver CFP2 supports 100 Gig PM-QPSK and 200 Gig PM-16-QAM schemes. "Some customers prefer the simplicity of a limiting interface; for the linear interface you have to do more calibration or set-up," says Blum. "Linear also allows you to do pre-emphasis of the signal path, from the DSP all the way to the modulator." Pre-emphasis is used to compensate for signal path impairments.
By consuming under 12W, up to eight line-side CFP2 interfaces can fit on a line card, says Blum, who also stresses the CFP2 has a 0dBm output power at 200 Gig. Achieving such an output power level means the 200 Gig signal is on a par with 100 Gig wavelengths. "When you launch a 200 Gig signal, you want to make sure that there is not a big difference between signals," says Blum.
To achieve the higher output power, the micro integrable tunable laser assembly (micro-iTLA) includes a semiconductor optical amplifier (SOA) with the laser, while SOAs are also added to the Mach–Zehnder modulator chip. "That allows us to compensate for some of the [optical] losses," says Blum.
Customers received first CFP2 samples in May, with the module currently at the design validation stage. Oclaro expects volume shipments to begin in the first half of 2015.
100 Gig and the data centre
Oclaro also announced at ECOC that it has expanded manufacturing capacity for its CFP2-based 100GBASE-LR4 10km-reach module.
One reason for the flurry of activity around 100 Gig mid-reach interfaces that span 500m-2km in the data centre is that the 100GBASE-LR4 module is relatively expensive. Oclaro itself has said it will support the PSM-4, CWDM4 and CLR4 Alliance mid-reach 100 Gig interfaces. So why is Oclaro expanding manufacturing of its CFP2-based 100GBASE-LR4?
It is about being pragmatic and finding the most cost-effective solution for a given problem
"There is no clear good solution to get 100 Gig over 500m or 2km right now," says Blum. "CFP2 is here, it is a mature technology and we have made improvements both in performance and cost."
Oclaro has improved its EML design such that the laser needs less cooling, reducing overall power dissipation. The accompanying electronic functions such as clock data recovery have also been redesigned using one IC instead of two such that the CFP2 -LR4's overall power consumption is below 8W.
Demand has been so significant, says Blum, that the company has been unable to meet customer demand. Oclaro expects that towards year-end, it will have increased its CFP2 100GBASE-LR4 manufacturing capacity by 50 percent compared to six months earlier.
"It is about being pragmatic and finding the most cost-effective solution for a given problem," says Blum. "There are other [module] variants that are of interest [to us], such as the CWDM4 MSA that offers a cost-effective way to get to 2km."
OIF prepares for virtual network services
The Optical Internetworking Forum has begun specification work for virtual network services (VNS) that will enable customers of telcos to define their own networks. VNS will enable a user to define a multi-layer network (layer-1 and layer-2, for now) more flexibly than existing schemes such as virtual private networks.
Vishnu Shukla"Here, we are talking about service, and a simple way to describe it [VNS] is network slicing," says OIF president, Vishnu Shukla. "With transport SDN [software-defined networking], such value-added services become available."
The OIF work will identify what carriers and system vendors must do to implement VNS. Shukla says the OIF already has experience working across multiple networking layers, and is undertaking transport SDN work. "VNS is a really valuable extension of the transport SDN work," says Shukla.
The OIF expects to complete its VNS Implementation Agreement work by year-end 2015.
Meanwhile, the OIF's Carrier Working Group has published its recommendations document, entitled OIF Carrier WG Requirements for Intermediate Reach 100G DWDM for Metro Type Applications, that provides input for the OIF's Physical Link Layer (PLL) Working Group.
The PLL Working Group is defining the requirements needed for a compact, low-cost and low-power 100 Gig interface for metro and regional networks. This is similar to the OIF work that successfully defined the first 100 Gig coherent modules in a 5x7-inch MSA.
The Carrier Working Group report highlights key metro issues facing operators. One is the rapid growth of metro traffic which, according to Cisco Systems, will surpass long-haul traffic in 2014. Another is the change metro networks are undergoing. The metro is moving from a traditional ring to a mesh architecture with the increasing use of reconfigurable optical add/drop multiplexers (ROADMs). As a result, optical wavelengths have further to travel, must contend with passing through more ROADMs stages and more fibre-induced signal impairments.
Shukla stresses there are differences among operators as to what is considered a metro network. For example, metro networks in North America span 400-600km typically and can be as much as 1,000km. In Europe such spans are considered regional or even long-haul networks. Metro networks also vary greatly in their characteristics. "Because of these variations, the requirements on optical modules varies so much, from unit to unit and area to area," says Shukla.
Given these challenges, operators want a module with sufficient optical performance to contend with the ROADM stages, and variable distances and network conditions encountered. "Sometimes we feel that the requirements [between metro and long-haul] won't be that much [different]," says Shukla. Indeed, the Carrier Working Group report discusses how the boundaries between metro and long-haul networks are blurring.
Yet operators also want such robust optical module performance at a greatly reduced price. One of the report's listed requirements is the need for the 100 Gig intermediate-reach interfaces to cost 'significantly' less than the cheapest long-haul 100 Gig.
To this aim, the report recommends that the 100 Gig pluggable optical modules such as the CFP or CFP2 be used. Standardising on industry-accepted pluggable MSAs will drive down cost as happened with the introduction of 100 Gig long haul 5x7-inch MSA modules.
Metro and regional coherent interfaces will also allow the specifications to be relaxed in terms of the DSP-ASIC requirements and the modulation schemes used. "When we come to the metro area, chances are that some of the technologies can be done more simply, and the cost will go down," says Shukla. Using pluggables will also increase 100 Gig line card densities, further reducing cost, while the report also favours the DSP-ASIC being integrated into the pluggable module, where possible.
Contributors to the Carrier Working Group report include representatives from China Telecom, Deutsche Telekom, Orange, Telus and Verizon, as well as module maker Acacia.
Verizon readies its metro for next-generation P-OTS
Verizon is preparing its metro network to carry significant amounts of 100 Gigabit traffic and has detailed its next-generation packet-optical transport system (P-OTS) requirements. The operator says technological advances in 100 Gig transmission and new P-OTS platforms - some yet to be announced - will help bring large scale 100 Gig deployments in the metro in the next year or so.
Glenn Wellbrock
The operator says P-OTS will be used for its metro and regional networks for spans of 400-600km. "That is where we have very dense networks," says Glenn Wellbrock, director of optical transport network architecture and design at Verizon. "The amount of 100 Gig is going to be substantially higher than it was in long haul."
Verizon announced in April that it had selected Fujitsu and Coriant for a 100 Gig metro upgrade. The operator has already deployed Fujitsu's FlashWave 9500 and the Coriant 7100 (formerly Tellabs 7100) P-OTS platforms. "The announcement [in April] is to put 100 Gig channels in that embedded base," says Wellbrock.
The operator has 4,000 reconfigurable optical add/ drop multiplexers (ROADMs) across its metro networks worldwide and all support 100 Gig channels. But the networks are not tailored for high-speed transmission and hence the cost of 100 Gig remains high. For example, dispersion compensation fibre, and Erbium-doped fibre amplifiers (EDFA) rather than hybrid EDFA-Raman are used for the existing links. "It [the network] is not optimised for 100 Gig but will support it, and we are using [100 Gig] on an as-needed basis," says Wellbrock.
The metro platform will be similar to those used for Verizon's 100 Gig long-haul in that it will be coherent-based and use advanced, colourless, directionless, contentionless and flexible-grid ROADMs. "But all in a package that fits in the metro, with a much lower cost, better density and not such a long reach," says Wellbrock.
The amount of 100 Gig is going to be substantially higher than it was in long haul
One development that will reduce system cost is the advent of the CFP2-based line-side optical module; another is the emergence of third- or fourth-generation coherent DSP-ASICs. "We are getting to the point where we feel it is ready for the metro," says Wellbrock. "Can we get it to be cost-competitive? We feel that a lot of the platforms are coming along."
The latest P-OTS platforms feature enhanced packet capabilities, supporting carrier Ethernet, multi-protocol label switching - transport profile (MPLS-TP), and high-capacity packet and Optical Transport Network (OTN) switching. Recently announced P-OTS platforms suited to Verizon's metro request-for-proposal include Cisco Systems' Network Convergence System (NCS) 4000 and Coriant's mTera. Verizon says it expects other vendors to introduce platforms in the next year.
Verizon still has over 250,000 SONET elements in its network. Many are small and reside in the access network but SONET also exists in its metro and regional networks. The operator is keen to replace the legacy technology but with such a huge number of installed network elements, this will not happen overnight.
Verizon's strategy is to terminate the aggregated SONET traffic at its edge central offices so that it only has to deal with large Ethernet and OTN flows at the network node. "We plan to terminate the SONET, peel out the packets and send them in a packet-optimised fashion," says Wellbrock. In effect, SONET is to be stopped from an infrastructure point of view, he says, by converting the traffic for transport over OTN and Ethernet.
SDN and multi-layer optimisation
The P-OTS platform, with its integrated functionality spanning layer-0 to layer-2, will have a role in multi-layer optimisation. The goal of multi-layer optimisation is to transport services on the most suitable networking layer, typically the lowest, most economical layer possible. Software-defined networking (SDN) will be used to oversee such multi-layer optimisation.
However, P-OTS, unlike servers used in the data centre, are specialist rather than generic platforms. "Optical stuff is not generic hardware," says Wellbrock. Each P-OTS platform is vendor-proprietary. What can be done, he says, is to use 'domain controllers'. Each vendor's platform will have its own domain controller, above which will sit the SDN controller. Using this arrangement, the vendor's own portion of the network can be operated generically by an SDN controller, while benefitting from the particular attributes of each vendor's platform using the domain controller.
There is always frustration; we always want to move faster than things are coming about
Verizon's view is that there will be a hierarchy of domain and SDN controllers."We assume there are going to be multiple layers of abstraction for SDN," says Wellbrock. There will be no one, overriding controller with knowledge of all the networking layers: from layer-0 to layer-3. Even layer-0 - the optical layer - has become dynamic with the addition of colourless, directionless, contentionless and flexible-grid ROADM features, says Wellbrock.
Instead, as part of these abstraction layers, there will be one domain that will control all the transport, and another that is all-IP. Some software element above these controllers will then inform the optical and IP domains how best to implement service tasks such as interconnecting two data centres, for example. The transport controller will then inform each layer its particular task. "Now I want layer-0 to do that, and that is my Ciena box; I need layer-1 to do this and that happens to be a Cyan box; and we need MPLS transport to do this, and that could be Juniper," says Wellbrock, pointing out that in this example, three vendor-domains are involved, each with its own domain controller.
Is Verizon happy with the SDN progress being made by the P-OTS vendors?
"There is always frustration; we always want to move faster than things are coming about," says Wellbrock. "The issue, though, is that there is nothing I see that is a showstopper."
MACOM acquires Mindspeed to boost 100 Gig offerings
Ray MoroneyThe Mindspeed acquisition increases the serviceable addressible market for MACOM, both geographical - the company will strengthen its presence in Asia Pacific - and by gaining new equipment vendor accounts. It also broadens MACOM's 100 Gigabit physical device portfolio.
"We are targeting the 100 Gig buildout and the growth coming from that," says Ray Moroney, product line manager, opto-device business unit at MACOM.
Mindpeed also makes a broad portfolio of crosspoint switches used in datacom equipment, and several families of communications processors.
With the acquisition of Mindspeed we have the full electronics bill-of-materials for CFP2 and CFP4 [module] client-side applications
MACOM entered opto-electronics with the acquisition of Optimai in 2011 that had long-haul and client-side modulator drivers and trans-impedance amplifiers (TIAs). Now with Mindspeed's products, MACOM can capture client-side designs with clock data recovery chips and quad-channel TIAs for 100 Gig modules. "With the acquisition of Mindspeed we have the full electronics bill-of-materials for CFP2 and CFP4 [module] client-side applications," says Moroney.
MACOM also gains silicon germanium technology alongside its indium phosphide and gallium arsenide technologies. Silicon germanium has a lower cost structure once a design is being made in volume production, says Moroney, but the R&D and mask costs are generally higher. Silicon germanium also allows significant integration. "It is BiCMOS in nature," says Moroney. "You can integrate full CMOS functionality into a design too." For example digital control can be added alongside analogue functions. Moroney says the company will use silicon germanium for high-performance analogue designs like TIAs as well as high-frequency millimeter wave and microwave applications.
The company is considering its options regarding the future of the communications processors arm of Mindspeed's business. "MACOM is very much an analogue/ RF company," says Moroney. "It [communications processors] is certainly not seen as a core area of investment for MACOM."
Verizon on 100G+ optical transmission developments
Source: Gazettabyte
Feature: 100 Gig and Beyond. Part 1:
Verizon's Glenn Wellbrock discusses 100 Gig deployments and higher speed optical channel developments for long haul and metro.
The number of 100 Gigabit wavelengths deployed in the network has continued to grow in 2013.
According to Ovum, 100 Gigabit has become the wavelength of choice for large wavelength-division multiplexing (WDM) systems, with spending on 100 Gigabit now exceeding 40 Gigabit spending. LightCounting forecasts that 40,000, 100 Gigabit line cards will be shipped this year, 25,000 in the second half of the year alone. Infonetics Research, meanwhile, points out that while 10 Gigabit will remain the highest-volume speed, the most dramatic growth is at 100 Gigabit. By 2016, the majority of spending in long-haul networks will be on 100 Gigabit, it says.
The market research firms' findings align with Verizon's own experience deploying 100 Gigabit. The US operator said in September that it had added 4,800, 100 Gigabit miles of its global IP network during the first half of 2013, to total 21,400 miles in the US network and 5,100 miles in Europe. Verizon expects to deploy another 8,700 miles of 100 Gigabit in the US and 1,400 miles more in Europe by year end.
"We expect to hit the targets; we are getting close," says Glenn Wellbrock, director of optical transport network architecture and design at Verizon.
Verizon says several factors are driving the need for greater network capacity, including its FiOS bundled home communication services, Long Term Evolution (LTE) wireless and video traffic. But what triggered Verizon to upgrade its core network to 100 Gig was converging its IP networks and the resulting growth in traffic. "We didn't do a lot of 40 Gig [deployments] in our core MPLS [Multiprotocol Label Switching] network," says Wellbrock.
The cost of 100 Gigabit was another factor: A 100 Gigabit long-haul channel is now cheaper than ten, 10 Gig channels. There are also operational benefits using 100 Gig such as having fewer wavelengths to manage. "So it is the lower cost-per-bit plus you get all the advantages of having the higher trunk rates," says Wellbrock.
Verizon expects to continue deploying 100 Gigabit. First, it has a large network and much of the deployment will occur in 2014. "Eventually, we hope to get a bit ahead of the curve and have some [capacity] headroom," says Wellbrock.
We could take advantage of 200 Gig or 400 Gig or 500 Gig today
Super-channel trials
Operators, working with optical vendors, are trialling super-channels and advanced modulation schemes such as 16-QAM (quadrature amplitude amplitude). Such trials involve links carrying data in multiples of 100 Gig: 200 Gig, 400 Gig, even a Terabit.
Super-channels are already carrying live traffic. Infinera's DTN-X system delivers 500 Gig super-channels using quadrature phase-shift keying (QPSK) modulation. Orange has a 400 Gigabit super-channel link between Lyon and Paris. The 400 Gig super-channel comprises two carriers, each carrying 200 Gig using 16-QAM, implemented using Alcatel-Lucent's 1830 photonic service switch platform and its photonic service engine (PSE) DSP-ASIC.
"We could take advantage of 200 Gig or 400 Gig or 500 Gig today," says Wellbrock. "As soon as it is cost effective, you can use it because you can put multiple 100 Gig channels on there and multiplex them."
The issue with 16-QAM, however, is its limited reach using existing fibre and line systems - 500-700km - compared to QPSK's 2,500+ km before regeneration. "It [16-QAM] will only work in a handful of applications - 25 percent, something of this nature," says Wellbrock. This is good for a New York to Boston, he says, but not New York to Chicago. "From our end it is pretty simple, it is lowest cost," says Wellbrock. "If we can reduce the cost, we will use it [16-QAM]. However, if the reach requirement cannot be met, the operator will not go to the expense of putting in signal regenerators to use 16-QAM do, he says.
Earlier this year Verizon conducted a trial with Ciena using 16-QAM. The goals were to test 16-QAM alongside live traffic and determine whether the same line card would work at 100 Gig using QPSK and 200 Gig using 16-QAM. "The good thing is you can use the same hardware; it is a firmware setting," says Wellbrock.
We feel that 2015 is when we can justify a new, greenfield network and that 100 Gig or versions of that - 200 Gig or 400 Gig - will be cheap enough to make sense
100 Gig in the metro
Verizon says there is already sufficient traffic pressure in its metro networks to justify 100 Gig deployments. Some of Verizon's bigger metro locations comprise up to 200 reconfigurable optical add/ drop multiplexer (ROADM) nodes. Each node is typically a central office connected to the network via a ROADM, varying from a two-degree to an eight-degree design.
"Not all the 200 nodes would need multiple 100 Gig channels but in the core of the network, there is a significant amount of capacity that needs to be moved around," says Wellbrock. "100 Gig will be used as soon as it is cost-effective."
Unlike long-haul, 100 Gigabit in the metro remains costlier than ten 10 Gig channels. That said, Verizon has deployed metro 100 Gig when absolutely necessary, for example connecting two router locations that need to be connected using 100 Gig. Here Verizon is willing to pay extra for such links.
"By 2015 we are really hoping that the [metro] crossover point will be reached, that 100 Gig will be more cost effective in the metro than ten times 10 [Gig]." Verizon will build a new generation of metro networks based on 100 Gig or 200 Gig or 400 Gig using coherent receivers rather than use existing networks based on conventional 10 Gig links to which 100 Gig is added.
"We feel that 2015 is when we can justify a new, greenfield network and that 100 Gig or versions of that - 200 Gig or 400 Gig - will be cheap enough to make sense."
Data Centres
The build-out of data centres is not a significant factor driving 100 Gig demand. The largest content service providers do use tens of 100 Gigabit wavelengths to link their mega data centres but they typically have their own networks that connect relatively few sites.
"If you have lots of data centres, the traffic itself is more distributed, as are the bandwidth requirements," says Wellbrock.
Verizon has over 220 data centres, most being hosting centres. The data demand between many of the sites is relatively small and is served with 10 Gigabit links. "We are seeing the same thing with most of our customers," says Wellbrock.
Technologies
System vendors continue to develop cheaper line cards to meet the cost-conscious metro requirements. Module developments include smaller 100 Gig 4x5-inch MSA transponders, 100 Gig CFP modules and component developments for line side interfaces that fit within CFP2 and CFP4 modules.
"They are all good," says Wellbrock when asked which of these 100 Gigabit metro technologies are important for the operator. "We would like to get there as soon as possible."
The CFP4 may be available by late 2015 but more likely in 2016, and will reduce significantly the cost of 100 Gig. "We are assuming they are going to be there and basing our timelines on that," he says.
Greater line card port density is another benefit once 100 Gig CFP2 and CFP4 line side modules become available. "Lower power and greater density which is allowing us to get more bandwidth on and off the card." sats Wellbrock.
Existing switch and routers are bandwidth-constrained: they have more traffic capability that the faceplate can provide. "The CFPs, the way they are today, you can only get four on a card, and a lot of the cards will support twice that much capacity," says Wellbrock.
With the smaller form factor CFP2 and CFP4, 1.2 and 1.6 Terabits card will become possible from 2015. Another possible development is a 400 Gigabit CFP which would achieve a similar overall capacity gains.
Coherent, not just greater capacity
Verizon is looking for greater system integration and continues to encourage industry commonality in optical component building blocks to drive down cost and promote scale.
Indeed Verizon believes that industry developments such as MSAs and standards are working well. Wellbrock prefers standardisation to custom designs like 100 Gigabit direct detection modules or company-specific optical module designs.
Wellbrock stresses the importance of coherent receiver technology not only in enabling higher capacity links but also a dynamic optical layer. The coherent receiver adds value when it comes to colourless, directionless, contentionless (CDC) and flexible grid ROADMs.
"If you are going to have a very cost-effective 100 Gigabit because the ecosystem is working towards similar solutions, then you can say: 'Why don't I add in this agile photonic layer?' and then I can really start to do some next-generation networking things." This is only possible, says Wellbrock, because of the tunabie filter offered by a coherent receiver, unlike direct detection technology with its fixed-filter design.
"Today, if you want to move from one channel to the next - wavelength 1 to wavelength 2 - you have to physically move the patch cord to another filter," says Wellbrock. "Now, the [coherent] receiver can simply tune the local oscillator to channel 2; the transmitter is full-band tunable, and now the receiver is full-band tunable as well." This tunability can be enabled remotely rather than requiring an on-site engineer.
Such wavelength agility promises greater network optimisation.
"How do we perhaps change some of our sparing policy? How do we change some of our restoration policies so that we can take advantage of that agile photonics later," says Wellbroack. "That is something that is only becoming available because of the coherent 100 Gigabit receivers."
Part 2, click here
ECOC 2013 review - Part 1
Gazettabyte surveys some of the notable product announcements made at the recent European Conference on Optical Communication (ECOC) held in London.
Part 1: Highlights
- First CFP4 module demonstration from Finisar
- Acacia Communications unveils first 100 Gig coherent CFP
- Oplink announces a 100 Gig direct detection CFP
- Second-generation coherent components take shape
100 Gigabit pluggables
Finisar used the ECOC exhibition to demonstrate the first CFP4 optical module, the smallest of the CFP MSA family of modules. The first CFP4 supports the 100GBASE-SR4 standard comprising four electrical and four optical channels, each at 25 Gigabit-per-second (Gbps).
The CFP4 is a quarter of the width of the CFP while the CFP2 is about a half the CFP's width. The CFP4 thus promises to quadruple the faceplate port density compared to using the CFP. Finisar says the CFP4 does even better, supporting line cards with 3.6 Terabits of capacity.
"It is not just the [CFP4's] width but the length and height that are shorter," says Rafik Ward, vice president of marketing at Finisar. The CFP4s can be aligned in two columns - belly-to-belly - on the card, achieving 3.6Tbps, each row comprising 18 CFP4 modules.
We see the CFP4 as a necessity to continue to grow the 100 Gigabit Ethernet market
The CFP4 was always scheduled to follow quickly the launch of the CFP2, says Ward. But the availability of the CFP4 will be important for the MSA. Data centre switch vendor Arista Networks has said that the CFP2 was late to market, while Cisco Systems has developed the CPAK, its own CFP2 alternative. "We see it [the CFP4] as a necessity to continue to grow the 100 Gigabit Ethernet market," says Ward.
Other 100 Gigabit Ethernet (GbE) variants will follow in the CFP4 form factor such as the LR4 and SR10 and the 10x10GbE breakout variant. This raises the interesting prospect of requiring an “inverse gearbox” chip that will translate between the CFP4's four electrical channels and the SR10's 10 optical channels. "We are going to see a lot of design activity around CFP4 in 2014," says Ward.
Meanwhile, Acacia Communications unveiled the AC-100, the first 100 Gig coherent CFP module for metro and regional networks, that includes a digital signal processor (DSP) system-on-chip.
"The DSP can be programmed for different performance and power levels to achieve a range of distances," says Daryl Inniss, vice president and practice leader components at market research firm, Ovum.
Acacia Communications says a CFP-based coherent design provides carriers and content providers with a 100 Gig metro solution that is more economical than 10 Gig.
Oplink Communications announced a direct detection 100 Gig metro CFP at ECOC. The 4x28Gbps CFP uses MultiPhy's maximum likelihood sequence estimation (MLSE) algorithm implemented using its MP1100Q and MP1101Q ICs. The devices enhance the reach of the module and allows 10 Gig optical components to be used for the receive and transmit paths. "Oplink’s CFP is the first module to come to market with our devices inside," says Neal Neslusan, vice president of marketing and sales at MultiPhy.
There are now at least three vendors selling direct-detection 100Gbps modules, says Neslusan, with Oplink and Menara Networks, which has also announced a CFP product, joining Finisar.
MultiPhy is working with several additional companies and that one system vendor will come to market with a product using the company's chips in the coming months. The company is also working on a second-generation direct detection IC design. "We believe there is a compelling roadmap story for direct detection," says Neslusan.
Oclaro announced it is now shipping in volume its 10km 100GBASE-LR4 CFP2 supporting 100GbE and OTU4 (OTN) rates. Oclaro has demonstrated the CFP2 working with a Xilinx Virtex 7 FPGA. "If customers choose that combination of technology, we have already tested it for them and they can rely on those rates [100GbE and OTU4] working," says Per Hansen, vice president of product marketing, optical networks solutions at Oclaro.
JDSU also said that its CFP2 LR4 is nearing completion. "We are getting pretty close to releasing it," says Brandon Collings, chief technology officer, communications and commercial optical products at JDSU.
Ed Murphy, JDSU
The integrated transmit and receive optical sub-assembly (TOSA/ ROSA) designs for the CFP2 LR4 use hybrid integration.
"In this case it is not monolithic integration as it is in the case of the indium phosphide line side modules but hybrid integration taking advantage of our PLC (planar lightwave circuit) technology in combination with arrays of photo detectors or high speed EMLs (externally modulated lasers)," says Murphy.
JDSU has based its module roadmap on the CFP2 TOSA and ROSA designs. The designs are sufficiently integrated to also fit within the QSFP28 and CFP4 modules.
There may be tweaks to the chips to lower the power dissipation, says Murphy, but these will be minor variants on existing parts.
Coherent components
Several component makers discussed their latest compact designs for next-generation coherent transmission line cards and modules.
NeoPhotonics detailed its micro-ITLA narrow linewidth tunable laser (micro-ITLA) that occupies less than a third of the area of the existing ITLA design. The company also announced a small form factor intradyne coherent receiver (SFF-ICR), less than half the size of existing integrated coherent receivers (ICRs).
NeoPhotonics supplies components to module and system vendors, and says customer interest in the second-generation coherent components is for higher port count line cards. "Instead of 100 Gig on a line card, you can have 200 or 400 Gigabit on a line card," says Ferris Lipscomb, vice president of marketing at NeoPhotonics. Moving to pluggable module designs will be a follow-on development, but for now, the market is not quite ready, he says.
An integrated coherent transmitter for metro, combining a tunable laser and integrated indium phosphide modulator in a compact package is also offered by NeoPhotonics.
The laser has two outputs - one output is modulated for the transmission while the second output is a local oscillator source feeding the coherent receiver. About half of all 100Gbps designs use such a split laser source, says Lipscomb, rather than two separate lasers, one each for the transmitter and the receiver. "That means that one transponder can only transmit and receive the same wavelength and is a little less flexible but for cost reduction that is what people are doing," says Lipscomb.
Oclaro is now sampling to customers its next-generation indium phosphide-based coherent components. The company, also a supplier of coherent modules, says the components will enable CFP and CFP2 pluggable coherent transceivers. The pluggable modules are suited for use in metro and metro regional networks.
Oclaro's components include an integrated transmitter comprising an indium phosphide laser and modulator, and the SFF-ICR. Oclaro's micro-ITLA is in volume production and has an output power high enough to perform both the transmit and the local oscillator functions. The micro-ITLA is used for line cards, 5x7-inch and 4x5-inch MSAs module and CFP designs.
u2t Photonics is another company that is developing a SFF-ICR. The company gave a private demonstration at ECOC to its customers of its indium phosphide modulator for use with CFP and CFP2 modules. "We demonstrated technical feasibility; it is a prototype which shows the capability of indium phosphide technology," says Jens Fiedler, executive vice president sales and marketing at u2t Photonics.
u2t Photonics and Finisar both licensed 100Gbps coherent indium phosphide modulator technology developed at the Fraunhofer Heinrich-Hertz-Institute.
There are new coherent DSP chips coming out early next year
Also showcased was u2t's gallium arsenide modulator technology implementing 16-QAM (quadrature amplitude modulation) at ECOC, but the company has yet to announce a product.
JDSU also gave an update on its line side coherent components. It is developing an integrated transmitter - a laser with nested modulators - for coherent applications. "This work is underway as a technology for line side CFP and CFP2 modules," says Ed Murphy, senior director, communications and commercial optical products at JDSU.
The difference between the CFP and CFP2 coherent modules is that the DSP system-on-chip is integrated within the CFP. Acacia's AC-100 CFP is the first example of such a product. For the smaller CFP2, the DSP will reside on the line card.
"There are new DSP [chips] coming out early next year," says Robert Blum, director of product marketing for Oclaro's photonic components. The DSPs will require a power consumption no greater than 20W if the complete design - the DSP and optics - is to comply with the CFP's maximum power rating of 32W.
Pluggable coherent modules promise greater port densities per line card. The modules can also be deployed with traffic demand and, in the case of a fault, can be individually swapped rather than having to replace the line card, says Blum.
JDSU says two factors are driving the metro coherent market. One is the need for lower cost designs to meet metro's cost-sensitive requirements. The second is that the metro distances can use essentially the same devices for 16-QAM to support 200Gbps links as well as 100Gbps. "It is the same modulator structure; maybe a few of the specs are a bit tighter but you can think of it as the same device," says Murphy.
System vendors have trialled 200Gbps links but deployments are expected to start from 2014. The deployments will likely use lithium niobate modulators, says Murphy, but will be followed quickly by indium phosphide designs.
NeoPhotonics used ECOC to declare that it has now integrated the semiconductor optical component arm of Lapis Semiconductor which it acquired for $35.2 million in March 2013.
Ferris Lipscomb
The unit, known as NeoPhotonics Semiconductor GK, makes drivers and externally modulated lasers. "These are key technologies for high-speed 100 Gig and 400 Gig transmissions, both on the line side and on the client side," says Lipscomb.
NeoPhotonics, previously a customer of Lapis, decided to acquire the unit and benefit from vertical integration as it expands its 100 Gig and higher-speed coherent portfolio.
Owning the technology has cost and optical performance benefits, says Lipscomb. It enables the integration of a design on one chip, thereby avoiding interfacing issues.
Further reading:
Part 2, click here
OIF demonstrates its 25 Gig interfaces are ready for use
The Open Internetworking Forum (OIF) has demonstrated its specified 25 and 28 Gigabit-per-second (Gbps) electrical interfaces working across various vendors' 100 Gigabit modules and ICs.
"The infrastructure over the backplane is maturing to the point of 25 Gig; you don't need special optical backplanes" John Monson, Mosys
"The ecosystem is maturing," says John Monson, vice president of marketing at Mosys, one of the 11 firms participating in the demonstrations. "The demos are not just showing the electrical OIF interfaces but their functioning between multiple vendors, with optical standards running across them at 100 Gig."
The demonstrations - using the CFP2, QSFP and CPAK optical modules and the 28Gbps CEI-28G-VSR module-to-chip electrical interface - set the stage for higher density 400 and 800 Gigabit line cards, says Monson. The CEI-28G-VSR is specified for up to 10dB of signal loss, equating to some 4 to 6 inches of trace on a high-quality material printed circuit board.
Higher density system backplanes are also ready using the OIF's CEI-25G-LR interface. "Until I get backplanes capable of high rates, there are just too many pins at 10 Gig to support 800 Gig and Terabit [line card] solutions," says Monson.
The ECOC demonstrations include two 100Gbps modules linked over fibre. "You have two CFP2 modules, from different vendors, running at 4x28Gbps OTN [Optical Transport Network] rates over 10km," says Monson.
On the host side, the CEI-28G-VSR interface sits between a retimer inside the CFP2 module and a gearbox chip that translates between 25Gbps and the 10Gbps lanes that link a framer or a MAC IC on the line card.
The demonstrations cover different vendors' gearbox ICs talking to different optical module makers' CFP2s as well as Cisco's CPAK. "We are mixing and matching quite a bit in these demos," says Monson.
The OIF has already started work for the next-generation electrical interfaces that follow the 25 and 28 Gigabit ones
There is also a demo of a QSFP+ module driving active copper cable and one involving two 100 Gigabit SR10 modules and a gearbox IC. Three further demos involve the CEI-25G-LR backplane interface. Lastly, there is a demo involving the thermal modelling of a line card hosting eight slots of the CDFP 400Gbps optical module MSA.
The OIF's CEI-25G-LR is specificed for up to 25dB of loss. The IEEE P802.3bj 100 Gbps Backplane and Copper Cable Task Force is specifying an enhanced backplane electrical interface that supports 35dB of loss using techniques such as forward error correction.
"What the demos say is that the electrical interfaces, at 25 Gig, can be used not just for a 4-6 inch trace, but also high-density backplanes," says Monson. As a result line card density will increase using the smaller form factor 100Gbps optical modules. It also sets the stage for 400 Gig individual optics, says Monson: "The infrastructure over the backplane is maturing to the point of 25 Gig; you don't need special optical backplanes."
Meanwhile, standards work for 400 Gigabit Ethernet is still at an early stage, but proposals for 56Gbps links have been submitted for consideration. "Such a rate would double capacity and reduce the number of pins required on the ASSPs and ASICs," says Monson.
As to how the electrical interface for 400 Gigabit Ethernet will be implemented, it could be 16x25Gbps or 8x50Gbps lanes and will also be influenced by the chosen optical implementation. The OIF has already started work for the next-generation electrical interfaces that follow the 25 and 28 Gigabit ones.
The 11 companies and the two test and measurement companies taking part, as well as the demonstrations, are detailed in an OIF White Paper, click here.
Arista Networks embeds optics to boost 100 Gig port density
Arista Networks' latest 7500E switch is designed to improve the economics of building large-scale cloud networks.
The platform packs 30 Terabit-per-second (Tbps) of switching capacity in an 11 rack unit (RU) chassis, the same chassis as Arista's existing 7500 switch that, when launched in 2010, was described as capable of supporting several generations of switch design.
"The CFP2 is becoming available such that by the end of this year there might be supply for board vendors to think about releasing them in 2014. That is too far off."
Martin Hull, Arista Networks
The 7500E features new switch fabric and line cards. One of the line cards uses board-mounted optics instead of pluggable transceivers. Each of the line card's ports is 'triple speed', supporting 10, 40 or 100 Gigabit Ethernet (GbE). The 7500E platform can be configured with up to 1,152 10GbE, 288 40GbE or 96 100GbE interfaces.
The switch's Extensible Operating System (EOS) also plays a key role in enabling cloud networks. "The EOS software, run on all Arista's switches, enables customers to build, manage, provision and automate these large scale cloud networks," says Martin Hull, senior product manager at Arista Networks.
Applications
Arista, founded in 2004 and launched in 2008, has established itself as a leading switch player for the high-frequency trading market. Yet this is one market that its latest core switch is not being aimed at.
"With the exception of high-frequency trading, the 7500 is applicable to all data centre markets," says Hull. "That it not to say it couldn't be applicable to high-frequency trading but what you generally find is that their networks are not large, and are focussed purely on speed of execution of their transactions." Latency is a key networking performance parameter for trading.
The 7500E is being aimed at Web 2.0 companies and cloud service providers. The Web 2.0 players include large social networking and on-line search companies. Such players have huge data centres with up to 100,000 servers.
The same network architecture can also be scaled down to meet the requirements of large 'Fortune 500' enterprises. "Such companies are being challenged to deliver private cloud as the same competitive price points as the public cloud," says Hull.
The 7500 switches are typically used in a two-tier architecture. For the largest networks, 16 or 32 switches are used on the same switching tier in an arrangement known as a parallel spine.
A common switch architecture for traditional IT applications such as e-mail and e-commerce uses three tiers of switching. These include core switches linked to distribution switches, typically a pair of switches used in a given area, and top-of-rack or access switches connected to each distribution pair.
For newer data centre applications such as social networking, cloud services and search, the computation requirements result in far greater traffic shared on the same tier of switching, referred to as east-west traffic. "What has happened is that the single pair of distribution switches no longer has the capacity to handle all of the traffic in that distribution area," says Hull.
Customers address east-west traffic by throwing more platforms together. Eight or 16 distribution switches are used instead of a pair. "Every access switch is now connected to each one of those 16 distribution switches - we call them spine switches," says Hull.
The resulting two-tier design, comprising access switches and distribution switches, requires that each access switch has significant bandwidth between itself and any other access switch. As a result, many 7500 switches - 16 or 32 - can be used in parallel at the distribution layer.
Source: Arista Networks
"If I'm a Fortune 500 company, however, I don't need 16 of those switches," says Hull. "I can scale down, where four or maybe two [switches] are enough." Arista also offers a smaller 4-slot chassis as well as the 8 slot (11 RU) 7500E platform.
7500E specification
The switch has a capacity of 30Tbps. When the switch is fully configured with 1,152 10GbE ports, it equates to 23Tbps of duplex traffic. The system is designed with redundancy in place.
"We have six fabric cards in each chassis," says Hull, "If I lose one, I still have 25 Terabits [of switching fabric]; enough forwarding capacity to support the full line rates on all those ports." Redundancy also applies to the system's four power supplies. Supplies can fail and the switch will continue to work, says Hull.
The switch can process 14.4 billion 64-byte packets a second. This, says Hull, is another way of stating the switch capacity while confirming it is non-blocking.
The 7500E comes with four line card options: three use pluggable optics while the fourth uses embedded optics, as mentioned, based on 12 10Gbps transmit and 12 10Gbps receive channels (see table).
Using line cards supporting pluggable optics provides the customer the flexibility of using transceivers with various reach options, based on requirements. "But at 100 Gigabit, the limiting factor for customers is the size of the pluggable module," says Hull.
Using a CFP optical module, each card supports four 100Gbps ports only. The newer CFP2 modules will double the number to eight. "The CFP2 is becoming available such that by the end of this year there might be supply for board vendors to think about releasing them in 2014," says Hull. "That is too far off."
Arista's board mounted optics delivers 12 100GbE ports per line card.
The board-mounted triple-speed ports adhere to the IEEE 100 Gigabit SR10 standard, with a reach of 150m over OM4 fibre. The channels can be used discretely for 10GbE, grouped in four for 40GbE, while at 100GbE they are combined as a set of 10.
"At 100 Gig, the IEEE spec uses 20 out of 24 lanes (10 transmit and 10 receive); we are using all 24," says Hull. "We can do 12 10GbE, we can do three 40GbE, but we can still only do one 100Gbps because we have a little bit left over but not enough to make another whole 100GbE." In turn, the module can be configured as two 40GbE and four 10GbE ports, or 40GbE and eight 10GbE.
Using board-mounted optics reduces the cost of 100Gbps line card ports. A full 96 100GbE switch configuration achieves a cost of $10k/port while using existing CFP modules the cost is $30k-50k/ port, claims Arista.
Arista quotes 10GbE as costing $550 per line card port not including the pluggable transceiver. At 40GbE this scales to $2,200. For 100GbE the $10k/ port comprises the scaled-up port cost at 100GbE ($2.2k x 2.5) to which is added the cost of the optics. The power consumption is under 4W/ port when the system is fully loaded.
The company uses merchant chips rather than an in-house ASIC for its switch platform. Can't other vendors develop similar performance systems based on the same ICs? "They could, but it is not easy," says Hull.
The company points out that merchant chip switch vendors use a CMOS process node that is typically a generation ahead of state-of-the-art ASICs. "We have high-performance forwarding engines, six per line card, each a discrete system-on-chip solution," says Hull. "These have the technology to do all the Layer 2 and Layer 3 processing." All these devices on one board talk to all the other chips on the other cards through the fabric.
In the last year, equipment makers have decided to bring silicon photonics technology in-house: Cisco Systems has acquired Lightwire while Mellanox Technologies has announced its plan to acquire Kotura.
Arista says it is watching silicon photonics developments with keen interest. "Silicon photonics is very interesting and we are following that," says Hull. "You will see over the next few years that silicon photonics will enable us to continue to add density."
There is a limit to where existing photonics will go, and silicon photonics overcomes some of those limitations, he says.
Extensible Operating System
Arista's highlights several characteristics of its switch operating system. The EOS is standards-compliant, self-healing, and supports network virtualisation and software-defined networking (SDN).
The operating system implements such protocols as Border Gateway Protocol (BGP) and spanning tree. "We don't have proprietary protocols," says Hull. "We support VXLAN [Virtual Extensible LAN] an open standards way of doing Layer 2 overlay of [Layer] 3."
EOS is also described as self-healing. The modular operating system is composed of multiple software processes, each process described as an agent. "If you are running a software process and it is killed because it is misbehaving, when it comes back typically its work is lost," says Hull. EOS is self-healing in that should an agent need to be restarted, it can continue with its previous data.
"We have software logic in the system that monitors all the agents to make sure none are misbehaving," says Hull. "If it finds an agent doing stuff that it should not, it stops it, restarts it and the process comes back running with the same data." The data is not packet related, says Hull, rather the state of the network.
The operating system also supports network virtualisation, one aspect being VXLAN. VXLAN is one of the technologies that allows cloud providers to provide a customer with server resources over a logical network when the server hardware can be distributed over several physical networks, says Hull. "Even a VLAN can be considered as network virtualisation but VXLAN is the most topical."
Support for SDN is an inherent part of EOS from its inception, says Hull. “EOS is open - the customers can write scripts, they can write their own C-code, or they can install Linux packages; all can run on our switches." These agents can talk back to the customer's management systems. "They are able to automate the interactions between their systems and our switches using extensions to EOS," he says.
"We encompass most aspects of SDN," says Hull. "We will write new features and new extensions but we do not have to re-architect our OS to provide an SDN feature."
Arista is terse about its switch roadmap.
"Any future product would improve performance - capacity, table sizes, price-per-port and density," says Hull. "And there will be innovation in the platform's software.
u2t Photonics pushes balanced detectors to 70GHz
- u2t's 70GHz balanced detector supports 64Gbaud for test and measurement and R&D
- The company's gallium arsenide modulator and next-generation receiver will enable 100 Gigabit long-haul in a CFP2
"The performance [of gallium arsenide] is very similar to the lithium niobate modulator"
Jens Fiedler, u2t Photonics
u2t Photonics has announced a balanced detector that operates at 70GHz. Such a bandwidth supports 64 Gigabaud (Gbaud), twice the symbol rate of existing 100 Gigabit coherent optical transmission systems.
The German company announced a coherent photo-detector capable of 64Gbaud in 2012 but that had an operating bandwidth of 40GHz. The latest product uses two 70GHz photo-detectors and different packaging to meet the higher bandwidth requirements.
"The achieved performance is a result of R&D work using our experience with 100GHz single photo-detectors and balanced detector technology at a lower speed,” says Jens Fiedler, executive vice president sales and marketing at u2t Photonics.
The monolithically-integrated balanced detector has been sampling since March. The markets for the device are test and measurement systems and research and development (R&D). "It will enable engineers to work on higher-speed interface rates for system development," says Fiedler.
The balanced detector could be used in next-generation transmission systems operating at 64 Gbaud, doubling the current 100 Gigabit-per-second (Gbps) data rate while using the same dual-polarisation, quadrature phase-shift keying (DP-QPSK) architecture.
A 64Gbaud DP-QPSK coherent system would halve the number of super-channels needed for 400Gbps and 1 Terabit transmissions. In turn, using 16-QAM instead of QPSK would further halve the channel count - a single dual-polarisation, 16-QAM at 64Gbaud would deliver 400Gbps, while three channels would deliver 1.2Tbps.
However, for such a system to be deployed commercially the remaining components - the modulator, device drivers and the DSP-ASIC - would need to be able to operate at twice the 32Gbaud rate; something that is still several years out. That said, Fiedler points out that the industry is also investigating baud rates in between 32 Gig and 64 Gig.
Gallium arsenide modulator
u2t acquired gallium arsenide modulator technology in June 2009, enabling the company to offer coherent transmitter as well as receiver components.
At OFC/NFOEC 2013, u2t Photonics published a paper on its high-speed gallium arsenide coherent modulator. The company's design is based on the Mach-Zehnder modulator specification of the Optical Internetworking Forum (OIF) for 100 Gigabit DP-QPSK applications.
The DP-QPSK optical modulation includes a rotator on one arm and a polarisation beam combiner at the output. u2t has decided to support an OIF compatible design with a passive polarisation rotator and combiner which could also be integrated on chip. The resulting coherent modulator is now being tested before being integrated with the free space optics to create a working design.
"The performance [of gallium arsenide] is very similar to the lithium niobate modulator," says Fiedler. "Major system vendors have considered the technology for their use and that is still ongoing."
The gallium arsenide modulator is considerably smaller than the equivalent lithium niobate design. Indeed u2t expects the technology's power and size requirements, along with the company's coherent receiver, to fit within the CFP2 optical module. Such a pluggable 100 Gigabit coherent module would meet long-haul requirements, says Fiedler.
The gallium arsenide modulator can also be used within the existing line-side 100 Gigabit 5x7-inch MSA coherent transponder. Fiedler points out that by meeting the OIF specification, there is no space saving benefit using gallium arsenide since both modulator technologies fit within the same dimensioned package. However, the more integrated gallium arsenide modulator may deliver a cost advantage, he says.
Another benefit of using a gallium arsenide modulator is its optical performance stability with temperature. "It requires some [temperature] control but it is stable," says Fiedler.
Coherent receiver
u2t's current 100Gbps coherent receiver product uses two chips, each comprising the 90-degree hybrid and a balanced detector. "That is our current design and it is selling in volume," says Fiedler. "We are now working on the next version, according to the OIF specification, which is size-reduced."
The resulting single-chip design will cost less and fit within a CFP2 pluggable module.
The receiver might be small enough to fit within the even smaller CFP4 module, concludes Fiedler.