Oclaro uses Acacia’s Meru DSP for its CFP2-DCO
Oclaro will use Acacia Communications’ coherent DSP for its pluggable CFP2 Digital Coherent Optics (CFP2-DCO) module. The module will be compatible with Acacia’s own CFP2-DCO, effectively offering customers a second source.
Tom Williams This is the first time Acacia is making its coherent DSP technology available to a fellow module maker, says Tom Williams, Acacia’s senior director, marketing.
Acacia benefits from the deal by expanding the market for its technology, while Oclaro gains access to a leading low-power coherent DSP, the Meru, and can bring to market its own CFP2-DCO product.
Williams says the move was encouraged by customers and that having a second source and achieving interoperability will drive CFP2-DCO market adoption. That said, Acacia is not looking for further module partners. “With two strong suppliers, we don’t see a need to add additional ones,” says Williams.
“This agreement is a sign that the market is reaching maturity, with suppliers transitioning from grabbing market share at all costs to more rational strategies,” says Vladimir Kozlov, CEO and founder of LightCounting Market Research.
CFP2-DCO
The CFP2-DCO is a dense wavelength-division multiplexing module that supports 100-gigabit and 200-gigabit data rates.
With the CFP2-DCO design, the coherent DSP sits within the module, unlike the CFP2 Analog Coherent Optics (CFP2-ACO) where the DSP chip is external, residing on the line card.
According to Kevin Affolter, Oclaro’s vice president strategic marketing, the company looked at several merchant and non-merchant coherent DSPs but chose the Meru due to its low power consumption and its support for 200 gigabits using 8-ary quadrature amplitude modulation (8-QAM) as well as the 16-QAM scheme. Using 8-QAM extends the optical reach of 200-gigabit wavelengths.
This agreement is a sign that the market is reaching maturity, with suppliers transitioning from grabbing market share at all costs to more rational strategies
At 100 gigabits the CFP2-DCO achieves long-haul distances of 2,000km whereas at 200 gigabit at 8-QAM, the reach is in excess of 1,000km. The 8-QAM requires a wider passband than the 16-QAM, however, such that in certain metro networks where the signal passes through several ROADM stages, it is better to use the 16-QAM mode, says Acacia.
Source: Acacia, Gazettabyte
Oclaro’s design will combine the Meru with its indium phosphide-based optics whereas Acacia’s CFP2-DCO uses silicon photonics technology. The power consumption of the CFP2-DCO module is of the order of 20W.
The two companies say their CFP2-DCO modules will be compatible with the multi-source agreement for open reconfigurable add-drop multiplexers (ROADMs). The Open ROADM MSA is backed by 16 companies, eight of which are operators. The standard currently only defines 100-gigabit transmission based on a hard-decision forward-error correction.
“There are several carriers, AT&T being the most prominent, within Open ROADM,” says Affolter. “It makes sense for both companies to make sure the needs of Open ROADM are addressed.”
Coherent shift
In 2017, Oclaro was one of three optical module companies that signed an agreement with Ciena to use the systems vendor’s WaveLogic Ai coherent DSP to develop a 400-gigabit transponder.
Kevin Affolter
Affolter says the Ciena and Acacia agreements should be seen as distinct; the 400-gigabit design is a large, 5x7-inch non-pluggable module designed for maximum reach and capacity. “The deals are complementary and this announcement has no impact on the Ciena announcement,” says Affolter.
Does the offering of proprietary DSPs to module makers suggest a shift in coherent that has always been seen as a strategic technology that allows for differentiation?
Affolter thinks not. “There are several vertically integrated vendors with their own DSPs that will continue to leverage their investment as much as they can,” he says. “But there is also an evolution of end customers and network equipment manufacturers that are moving to more pluggable solutions and that is where the -DCO really plays.”
Oclaro expects to have first samples of its CFP2-DCO by year-end. Meanwhile, Acacia’s CFP2-DCO has been generally available for over six months.
Elenion's coherent and fibre-to-the-server plans
- Elenion’s coherent chip - an integrated modulator-receiver assembly - is now generally available.
- The company has a silicon photonics design library that includes over 1,000 elements.
- Elenion is also developing an optical engine for client-side interfaces.
Elenion Technologies has given an update on its activities and strategy after announcing itself eight months ago. The silicon photonics-based specialist is backed by private equity firm, Marlin Equity Partners, which also owns systems vendor, Coriant. Elenion had already been active for two and a half years and shipping product when it emerged from its state of secrecy last December.
Larry SchwerinElenion has since announced it is selling its telecom product, a coherent transceiver PIC, to Coriant and now other companies.
It has also progressed its optical engine design for the data centre that will soon be a product. Elenion has been working with Ethernet switch chip maker, Cavium, and data centre player, Microsoft, as part of its datacom work.
“We have moved forward,” says Larry Schwerin, the CEO of Elenion.
Coherent PIC
Elenion’s integrated modulator-receiver assembly is being used by Coriant for two CFP2 Analogue Coherent Optics (CFP2-ACO) modules as part of its Groove G30 platform.
The first is a short-reach CFP2-ACO for point-to-point 200-gigabit links that has a reach of at least 80km. The second is a high-performance CFP2-ACO that has a reach of up to 4,000km at 100 gigabits and 650km at 200 gigabits.
Schwerin says the company is now selling the coherent PIC to “a lot of people”. In addition to the CFP2-ACO, there is the Digital Coherent Optics (DCO) pluggable market where the PIC and the coherent digital signal processor (DSP) are integrated within the module. Examples include the CFP-DCO and the smaller CFP2-DCO which is now being designed into new systems. ADVA Optical Networking is using the CFP2-DCO for its Teraflex, as is its acquisition target MRV with its 200-gigabit coherent muxponder. Infinera’s latest XTM II platforms also use the CFP2-DCO.
We have got a library that has well over 1,000 elements
Using silicon photonics benefits the cost and performance of the coherent design, says Schwerin. The cost benefit is a result of optical integration. “You can look at it as a highly simplified supply chain,” says Schwerin. Coupling the electronics close to the optics also optimises overall performance.
Elenion is also targeting the line-card market for its coherent PIC. “This is one of the reasons why I wanted to stay out of the pluggable business,” says Schwerin. “There are a lot more customers out there if you stay out of pluggables because now you are selling an [optical] engine.”
The company is also developing a coherent PIC design that will support higher data rates such as 400- and 600-gigabit per lambda. “Without being too specific because we do remain stealthy, we have plans to support these applications,” says Schwerin.
Schwerin stresses that the real strength of the company is its design library used to develop its silicon photonics circuits. Elenion emerged out of a silicon photonics design-for-service company. “We have got a library that has well over 1,000 elements,” he says. Elenion says it can address custom design requests of companies using its design library.
Datacom
Elenion announced at the OFC show held in Los Angeles in March that it is working with Jabil AOC Technologies, a subsidiary of the manufacturing firm, Jabil Circuits. Elenion chose the contract manufacturer due to its ability to address both line-card and pluggable designs, the markets for its optical engines.
The two firms have also been working at the chip level on such issues as fibre attach, coupling the laser and adding the associated electronics. “We are trying to make the interface as elegant and streamlined as possible,” says Schwerin. “We have got initiatives underway so that you don't need these complex arrangements.”
Schwerin highlights the disparity between the unit volumes needed for the telecom and datacom markets. According to forecasts from market research firms, the overall coherent market is expected to grow to 800,000 and 1 million units a year by 2020. In contrast, the interfaces used inside one large-scale data centre can be up to 2 million. “To achieve rapid manufacturing and yield, you have got to simplify the process,” he says.
This is what Elenion is tackling. If 1,000 die can be made on a single silicon wafer, and knowing the interface volumes required and the yields, the total number of wafer runs can be determined. And it is the overall time taken from starting a wafer to the finished transceiver PIC output that Elenion is looking to shorten, says the CEO.
We ran that demo from 7 AM to 2 AM every day of the show
At OFC, Elenion hired a hotel suite near the convention centre to demonstrate its technologies to interested companies. One demonstration used its 25Gbps optical engine directly mounted on a Cavium QLogic network interface card (NIC) connecting a server to a high-capacity Cavium Xpliant Ethernet switch chip. The demo showed how 16 NICs could be connected to the switch chip for a total capacity of 400 gigabits. “No more direct-attached cables or active optical cables, literally fibre-to-the-server,” says Schwerin. “We ran that demo from 7 AM to 2 AM every day of the show.”
Elenion’s on-board optics design was based on the emerging Consortium of On-Board Optics (COBO) standard. “The Microsoft folks, we work with them closely, so obviously what we are doing follows their intent,” says Schwerin.
The optical engine will also support 56Gbps links when used with four-level pulse-amplitude modulation (PAM-4) and the company is even eyeing 100Gbps interfaces. For now, Elenion’s datacom optical engine remains a technical platform but a product will soon follow.
The company’s datacom work is also benefiting its telecom designs. “The platform technology that we use for datacom has now found its way into the coherent programme, especially around the packaging,” says Schwerin.
* The article was changed on July 25th to mention that Elenion's PIC is being used in two Coriant CFP-ACOs.
Acacia looks to co-package its coherent PIC and DSP-ASIC
- Acacia Communications is working to co-package its coherent DSP and its silicon photonics transceiver chip.
- The company is also developing a digital coherent optics module that will support 400 gigabit.
Acacia Communications is working to co-package its coherent DSP and its silicon photonics transceiver chip. The line-side optical transceiver company is working on a digital coherent optics module that will support 400 gigabits.
Acacia announced last November that it was sampling the industry’s first CFP2 Digital Coherent Optics (CFP2-DCO) that supports 100- and 200-gigabit line rates. The CFP2-DCO integrates the DSP and its silicon photonics chip within a CFP2 module, which is half the size of a CFP module, with each chip packaged separately.
The CFP2-DCO adds to the company’s CFP2-ACO design that was announced a year ago. In the CFP2-ACO, the CFP2 module contains just the optics with the DSP-ASIC chip on the same line card connected to the module via a special high-speed interface connector.
Now, Acacia is working to co-package the two chips, which will not only improve the performance of its CFP2-DCO but also enable new, higher-performance optical modules such as a 400-gigabit DCO. The Optical Internetworking Forum announced a new implementation agreement last December for an interoperable 400-gigabit ZR (80km) coherent interface.
Both [the DSP and silicon photonics chip] are based on CMOS processes. The next step for Acacia is to bring them into a single package.
Portfolio upgrades
Acacia has also upgraded its existing portfolio of coherent transceivers. The company has integrated the enhanced silicon photonics coherent transceiver in its AC100-CFP and its AC-400 5x7-inch modules.
The silicon-photonics transceiver achieves a more efficient coupling of light in and out of the chip and uses an improved modulator driver design that reduces the overall power consumption. The design also supports flexible grid, enabling channel sizes of 37.5GHz in addition to fixed-grid 50GHz channels.
The resulting AC100-CFP module has a greater reach of 2,500km and a lower power consumption than the first generation design announced in 2014. The enhanced PIC has also been integrated within the AC-400. The AC-400, announced in 2015, integrates two silicon photonics chips to support line rates of 200, 300 and 400 gigabits.
CFP2-DCO
Acacia is using the coherent transceiver photonic integrated circuit (PIC), first used in its CFP2-ACO, alongside a new coherent DSP to integrate the optics and DSP within the compact CFP2.
“The third-generation PIC is a mini PIC; in a gold box that is about the size of a dime, which is a third of the size of our original PIC,” says Benny Mikkelsen, founder and CTO of Acacia.
One design challenge with its latest DSP was retaining the reach of the original DSP used in the AC100-CFP while lowering its power consumption. Having an inherently low-power coherent DSP design in the first place is one important factor. Mikkelsen says this is achieved based on several factors such as the DSP algorithms chosen and how they are implemented in hardware, the clock frequencies used within the chip, how the internal busses are implemented, and the choice of bits-per-symbol used for the processing.
The resulting DSP’s power consumption can be further reduced by using an advanced CMOS process. Acacia uses a 16nm CMOS process for its latest DSP.
Other challenges to enable a CFP2-DCO module include reducing the power consumption of the optics and reducing the packaging size. “The modulator driver is the piece part that consumes the most power on the optics side,” says Mikkelsen.
Acacia's CFP2-DCO supports polarisation multiplexing, quadrature phase-shift keying (PM-QPSK) for 100 gigabits, and two modulation schemes: polarisation multiplexing, 8-ary quadrature amplitude multiplexing (PM-8QAM) and 16-ary QAM - for 200-gigabit line rates. In contrast, its -ACO supports just PM-QPSK and PM-16QAM.
At 100 gigabits, the DSP consumes about half the power of the Sky DSP used in the original AC100. Using PM-8QAM for 200 gigabits means the new DSP and optics support a higher baud rate - some 45 gigabaud compared to the traditional 32-35 gigabaud used for 100 and 200-gigabit transmission. However, while this increases the power consumption, the benefit of 8QAM is a 200-gigabit reach beyond 1,000km.
Mikkelsen stresses that a key reason the company can achieve a CFP2-DCO design is having both technologies in-house: “You can co-optimise the DSP and the silicon photonics”.
We think, at least in the near term, that the OSPF module seems to be a good form factor to work on
ACO versus DCO
Since Acacia now offers both the CFP2-ACO and CFP2-DCO modules, it is less concerned about how the relative demand for the two modules develops. “We don’t care too much which one is going to have the majority of the market,” says Mikkelsen. That said, Acacia believes that the CFP2-DCO market will become the larger of the two.
When the CFP2-ACO was first considered several years ago, the systems vendors and optical module makers shared a common interest. Systems vendors wanted to use their custom coherent DSP-ASICs while the -ACO module allowed component makers that didn't have the resources to develop their own DSP to address the market with their optics. It was also necessary to separate the DSP and the optics if the smaller CFP2 form factor was to be used.
But bringing CFP2-ACOs to volume production has proved more difficult than first envisaged. The CFP2-DCO is far easier to use, says Mikkelsen. The module can be plugged straight into equipment whereas the CFP2-ACO must be calibrated by a skilled optical engineer when a wavelength is first turned up.
Future work
Acacia is now looking at new module form factors and new packaging technologies. “Both [the DSP and silicon photonics chip] are based on CMOS processes,” says Mikkelsen. “The next step for Acacia is to bring them into a single package.”
In addition to the smaller size, a single package promises a slightly lower power consumption as well as manufacturing cost advantages. “We also expect to see higher performance once the DSP and optics are sitting next to each other which we believe will improve signal integrity between the two,” says Mikkelsen.
Acacia is not waiting for any industry challenges to be overcome for a single-package design to be achieved. The company points out that its silicon photonics chip is not temperature sensitive, aiding its co-packaging with the DSP.
Acacia is working on a 400-gigabit DCO design and is looking at several potential module types. The company is a member of the OSFP module MSA as well as the Consortium of On-Board Optics (COBO) which has started a coherent working group. “We think, at least in the near term, that the OSPF module seems to be a good form factor to work on,” says Mikkelsen.
NeoPhotonics samples its first CFP-DCO products
The company has announced two such CFP Digital Coherent Optics (CFP-DCO) modules: a 100 gigabit-per-second (Gbps) module and a dual-rate 100Gbps and 200Gbps one.
“Our rationale [for entering the CFP-DCO market] is we have all the optical components and the [merchant coherent] DSPs are now becoming available,” says Ferris Lipscomb (pictured), vice president of marketing at NeoPhotonics. “It is possible to make this product without developing your own custom DSP, with all the expense that entails.”
-DCO versus -ACO
The pluggable transceiver line-side market is split between Digital Coherent Optics and Analog Coherent Optics (ACO) modules.
Optical module makers are already supplying the more compact CFP2 Analog Coherent Optics (CFP2-ACO) transceivers. The CFP2-ACO integrates the optics only, with the accompanying coherent DSP-ASIC chip residing on the line card. The CFP2-ACO suits system vendors that have their own custom DSP-ASICs and can offer differentiated, higher-transmission performance while choosing the optics in a compact pluggable module from several suppliers.
In contrast, the CFP-DCO suits more standard deployments, and for those end-customers that do not want to be locked into a single vendor and a proprietary DSP. The -DCO is also easier to deploy. In China, currently undertaking large-scale 100-gigabit optical transport deployments, operators want a module that can be deployed in the field by a relatively unskilled technician. Deploying an ACO requires an engineer to perform the calibration due to the analogue interface between the module and the DSP, says NeoPhotonics.
The DCO also suits those systems vendors that do not have their own DSP and do not want to source a merchant coherent DSP and implement the analogue integration on the line card.
Our rationale [for entering the CFP-DCO market] is we have all the optical components and the [merchant coherent] DSPs are now becoming available
One platform, two products
The two announced ClearLight CFP-DCO products are a 100 gigabit-per-second (Gbps) module implemented using polarisation multiplexing, quadrature phase-shift keying modulation (PM-QPSK), and a module that supports both 100Gbps and 200Gbps using PM-QPSK and 16 quadrature amplitude modulation (PM-16QAM), respectively.
The two modules share the same optics and DSP-ASIC. Where they differ is in the software loaded onto the DSP and the host interface used. The lower-speed module has a 4 by 25-gigabit interface whereas the 200-gigabit CFP-DCO uses an 8 by 25-gigabit-wide interface. “The 100-gigabit CFP-DCO plugs into existing client-side slots whereas the 200-gigabit CFPs have to plug into custom designed equipment slots,” says Lipscomb.
The 100-gigabit CFP-DCO has a reach of 1,000km plus and has a power consumption under 24W. Lipscomb points out that the actual specs including the power consumption are negotiated on a customer-by-customer basis. The 200-gigabit CFP-DCO has a reach of 500km.
NeoPhotonics says it is using a latest-generation 16nm CMOS merchant DSP. NTT Electronics (NEL) and Clariphy have both announced 16nm CMOS coherent DSPs.
“We are designing to be able to second-source the DSP,” says Lipscomb. “There are currently only two merchant suppliers but there are others that have developments but are not yet at the point where they would be in the market.”
The CFP-DCO modules also support flexible grid that can fit a carrier within the narrower 37.5GHz channel to increase overall transmission capacity sent across a fibre’s C-band.
NeoPhotonics’s 100Gbps CFP-DCO is already sampling and it expected to be generally available in mid-2017, while the 200Gbps CFP-DCO is expected to be available one-quarter later.
“For 200-gigabit, you need to have customers building slots,” says Lipscomb. “For 100-gigabit, there are lots of slots available that you can plug into; 200-gigabits will take a little bit longer.”
NeoPhotonics’ CFP-DCO delivers the line rate used by the Voyager white box packet optical switch being developed as part of the Telecom Infra Project backed by Facebook and ten operators including Deutsche Telekom and SK Telecom. But the one-rack-unit Voyager packet optical platform uses four 5"x7" modules not pluggable CFP-DCOs to achieve the total line rate of 800Gbps.
Roadmap
NeoPhotonics is developing coherent module designs that will use higher baud rates than the standard 32-35 gigabaud (Gbaud), such as 45Gbaud and 64Gbaud.
The company also plans to develop a CFP2-DCO. Such a module is expected around 2018 once lower-power DSP-ASICs become available that can fit within the 12W power envelope of the CFP2. Such merchant DSP-ASICs will likely be implemented in a more advanced CMOS process such as 12nm or even 7nm.
Acacia Communications is already sampling a CFP2-DCO. Acacia designs its own silicon photonics-based optics and the coherent DSP-ASIC.
NeoPhotonics is also considered future -ACO designs beyond the CFP2 such as the CFP8, the 400-gigabit OSFP form factor and even the CFP4. “We are studying it but we don't know yet which directions things are going to go,” says Lipscomb.
Corrected on Dec 22nd. The Voyager box does not use pluggable CFP-DCO modules.
Talking markets: Oclaro on 100 gigabits and beyond
Oclaro’s chief commercial officer, Adam Carter, discusses the 100-gigabit market, optical module trends, silicon photonics, and why this is a good time to be an optical component maker.
Oclaro has started its first quarter 2017 fiscal results as it ended fiscal year 2016 with another record quarter. The company reported revenues of $136 million in the quarter ending in September, 8 percent sequential growth and the company's fifth consecutive quarter of 7 percent or greater revenue growth.
Adam CarterA large part of Oclaro’s growth was due to strong demand for 100 gigabits across the company’s optical module and component portfolio.
The company has been supplying 100-gigabit client-side optics using the CFP, CFP2 and CFP4 pluggable form factors for a while. “What we saw in June was the first real production ramp of our CFP2-ACO [coherent] module,” says Adam Carter, chief commercial officer at Oclaro. “We have transferred all that manufacturing over to Asia now.”
The CFP2-ACO is being used predominantly for data centre interconnect applications. But Oclaro has also seen first orders from system vendors that are supplying US communications service provider Verizon for its metro buildout.
The company is also seeing strong demand for components from China. “The China market for 100 gigabits has really grown in the last year and we expect it to be pretty stable going forward,” says Carter. LightCounting Market Research in its latest optical market forecast report highlights the importance of China’s 100-gigabit market. China’s massive deployments of FTTx and wireless front haul optics fuelled growth in 2011 to 2015, says LightCounting, but this year it is demand for 100-gigabit dense wavelength-division multiplexing and 100 Gigabit Ethernet optics that is increasing China’s share of the global market.
The China market for 100 gigabits has really grown in the last year and we expect it to be pretty stable going forward
QSFP28 modules
Oclaro is also providing 100-gigabit QSFP28 pluggables for the data centre, in particular, the 100-gigabit PSM4 parallel single-mode module and the 100-gigabit CWDM4 based on wavelength-division multiplexing technology.
2016 was expected to be the year these 100-gigabit optical modules for the data centre would take off. “It has not contributed a huge amount to date but it will start kicking in now,” says Carter. “We always signalled that it would pick up around June.”
One reason why it has taken time for the market for the 100-gigabit QSFP28 modules to take off is the investment needed to ramp manufacturing capacity to meet the demand. “The sheer volume of these modules that will be needed for one of these new big data centres is vast,” says Carter. “Everyone uses similar [manufacturing] equipment and goes to the same suppliers, so bringing in extra capacity has long lead times as well.”
Once a large-scale data centre is fully equipped and powered, it generates instant profit for an Internet content provider. “This is very rapid adoption; the instant monetisation of capital expenditure,” says Carter. “This is a very different scenario from where we were five to ten years ago with the telecom service providers."
Data centre servers and their increasing interface speed to leaf switches are what will drive module rates beyond 100 gigabits, says Carter. Ten Gigabit Ethernet links will be followed by 25 and 50 Gigabit Ethernet. “The lifecycle you have seen at the lower speeds [1 Gigabit and 10 Gigabit] is definitely being shrunk,” says Carter.
Such new speeds will spur 400-gigabit links between the data centre's leaf and spine switches, and between the spine switches. “Two hundred Gigabit Ethernet may be an intermediate step but I’m not sure if that is going to be a big volume or a niche for first movers,” says Carter.
400 gigabit CFP8
Oclaro showed a prototype 400-gigabit module in a CFP8 module at the recent ECOC show in September. The demonstrator is an 8-by-50 gigabit design using 25 gigabaud optics and PAM-4 modulation. The module implements the 400Gbase-LR8 10km standard using eight 1310nm distributed feedback lasers, each with an integrated electro-absorption modulator. The design also uses two 4-wide photo-detector arrays.
“We are using the four lasers we use for the CWDM4 100-gigabit design and we can show we have the other four [wavelength] lasers as well,” says Carter.
Carter says IP core routers will be the main application for the 400Gbase-LR8 module. The company is not yet saying when the 400-gigabit CFP8 module will be generally available.
We can definitely see the CFP2-ACO could support 400 gigabits and above
Coherent
Oclaro is already working with equipment customers to increase the line-side interface density on the front panel of their equipment.
The Optical Internetworking Forum (OIF) has already started work on the CFP8-ACO that will be able to support up to four wavelengths, each supporting up to 400 gigabits. But Carter says Oclaro is working with customers to see how the line-side capacity of the CFP2-ACO can be advanced. “We can definitely see the CFP2-ACO could support 400 gigabits and above,” says Carter. “We are working with customers as to what that looks like and what the schedule will be.”
And there are two other pluggable form factors smaller than the CFP2: the CFP4 and the QSFP28. “Will you get 400 gigabits in a QSFP28? Time will tell, although there is still more work to be done around the technology building blocks,” says Carter.
Vendors are seeking the highest aggregate front panel density, he says: “The higher aggregate bandwidth we are hearing about is 2 terabits but there is a need to potentially going to 3.2 and 4.8 terabits.”
Silicon photonics
Oclaro says it continues to watch closely silicon photonics and to question whether it is a technology that can be brought in-house. But issues remain. “This industry has always used different technologies and everything still needs light to work which means the basic III-V [compound semiconductor] lasers,” says Carter.
“Producing silicon photonics chips versus producing packaged products that meet various industry standards and specifications are still pretty challenging to do in high volume,” says Carter. And integration can be done using either silicon photonics or indium phosphide. “My feeling is that the technologies will co-exist,” says Carter.
600-gigabit channels on a fibre by 2017
NeoPhotonics has announced an integrated coherent receiver that will enable 600-gigabit optical transmission using a single wavelength. A transmission capacity of 48 terabits over the fibre’s C-band is then possible using 80 such channels.
NeoPhotonics’ micro integrated coherent receiver operates at 64 gigabaud, twice the symbol rate of deployed 100-gigabit optical transport systems and was detailed at the recent ECOC show.
Current 100 gigabit-per-second (Gbps) coherent systems use polarisation-multiplexing, quadrature phase-shift keying (PM-QPSK) modulation operating at 32 gigabaud. “That is how you get four bits [per symbol],” says Ferris Lipscomb, vice president of marketing at NeoPhotonics.
Optical designers have two approaches to increase the data transmitted on a wavelength: they can use increasingly complex modulation schemes - such as 16 quadrature amplitude modulation (16-QAM) or 64-QAM - and they can increase the baud rate. “You double the baud rate, you double the transmission capacity,” says Lipscomb. “And using 64-QAM and 64 gigabaud, you can go to 600 gigabit per channel; of course when you do that, you reduce the reach.”
The move to the higher 64 gigabaud symbol rate will help Internet content providers increase capacity between their large-scale data centres. Typical transmission distances between sites are relatively short, up to 100km.
Telcos too will benefit from the higher baud rate as it will enable them to use software-defined networking to adapt, on-the-fly, a line card’s data rate and reach depending on the link. Such a flexible rate coherent line card would allow 600Gbps on a single channel over 80km, 400 gigabit (16-QAM) over 400km, or 100 gigabit over thousands of kilometers.
Status
NeoPhotonics says it is now sampling its 64 gigabaud coherent receiver. It is still premature to discuss when the high-speed coherent receiver will be generally available, the company says, as it depends on the availability of other vendors’ components working at 64 gigabaud. These include the modulator, the trans-impedance amplifier and the coherent digital signal processor ASIC (DSP-ASIC).
Lipscomb says that a 64-gigabaud modulator in lithium niobate already exists but not in indium phosphide. The lithium niobate modulator is relatively large and will fit within a CFP module but the smaller CFP2 module will require a 64-gigabaud indium phosphide modulator.
“General availability will be timed based on when our customers are ready to go into production,” says Lipscomb. “Trials will happen in the first half of 2017 with volume shipments only happening in the second half of next year.”
Using 64-QAM and 64 gigabaud, you can go to 600 gigabit per channel
Challenges
A micro integrated coherent receiver has two inputs - the received optical signal and the local oscillator - and four balanced receiver outputs. Also included are two polarisation beam splitters and two 90-degree hybrid mixers.
Lipscomb says Neophotonics worked for over a year to develop its coherent receiver: “It is a complete design from the ground up.”
The slowest element sets the speed at which the receiver can operator such that the design not only involves the detector and trans-impedance amplifier but other elements such as the wirebonds and the packaging. “Everything has to be upgraded,” says Lipscomb. “It is not just a case of plopping in a faster detector and everything works.”
Nano-ICR and the CFP2-DCO
The industry is now working on a successor, smaller coherent detector dubbed the nano integrated coherent receiver (nano-ICR). “It has not all gelled yet but the nano-ICR would be suitable for the CFP2-DCO.”
The CFP2-DCO is a CFP2 Digital Coherent Optics pluggable module that integrates the coherent DSP-ASIC. In contrast, the CFP2 Analog Coherent Optics (CFP2-ACO) modules holds the optics and the DSP-ASIC resides on the line card.
“As the new DSPs come out using the next CMOS [process] nodes, they will be lower power and will be accommodated in the CFP2 form factor,” says Lipscomb. “Then the optics has to shrink yet again to make room for the DSP.”
Lipscomb sees the CFP2-ACO being used by system vendors that have already developed their own DSP-ASICs and will offer differentiated, higher-transmission performance. The CFP2-DCO will be favoured for more standard deployments and by end-customers that do not want to be locked into a single vendor and a proprietary DSP.
There is also the CFP2-DCO’s ease of deployment. In China, currently undertaking large-scale 100-gigabit optical transport deployments, operators want a module that can be deployed in the field by a relatively unskilled technician. “The ACOs with the analogue interface tend to require a lot of calibration,” says Lipscomb. “You can’t just plug it in and it works; you have to run it in, calibrate it and bring it up to get it to work properly.”
The CFP2-DCO module is expected in 2018 as the DSP-ASICs will require an advanced 12nm or even 7nm CMOS process.
QSFP28 MicroMux expands 10 & 40 Gig faceplate capacity
- ADVA Optical Networking's MicroMux aggregates lower rate 10 and 40 gigabit client signals in a pluggable QSFP28 module
- ADVA is also claiming an industry first in implementing the Open Optical Line System concept that is backed by Microsoft
The need for terabits of capacity to link Internet content providers’ mega-scale data centres has given rise to a new class of optical transport platform, known as data centre interconnect.
Source: ADVA Optical Networking
Such platforms are designed to be power efficient, compact and support a variety of client-side signal rates spanning 10, 40 and 100 gigabit. But this poses a challenge for design engineers as the front panel of such platforms can only fit so many lower-rate client-side signals. This can lead to the aggregate data fed to the platform falling short of its full line-side transport capability.
ADVA Optical Networking has tackled the problem by developing the MicroMux, a multiplexer placed within a QSFP28 module. The MicroMux module plugs into the front panel of the CloudConnect, ADVA’s data centre interconnect platform, and funnels either 10, 10-gigabit ports or two, 40-gigabit ports into a front panel’s 100-gigabit port.
"The MicroMux allows you to support legacy client rates without impacting the panel density of the product," says Jim Theodoras, vice president of global business development at ADVA Optical Networking.
Using the MicroMux, lower-speed client interfaces can be added to a higher-speed product without stranding line-side bandwidth. An alternative approach to avoid wasting capacity is to install a lower-speed platform, says Theodoras, but then you can't scale.
ADVA Optical Networking offers four MicroMux pluggables for its CloudConnect data centre interconnect platform: short-reach and long-reach 10-by-10 gigabit QSFP28s, and short-reach and intermediate-reach 2-by-40 gigabit QSFP28 modules.
The MicroMux features an MPO connector. For the 10-gigabit products, the MPO connector supports 20 fibres, while for the 40-gigabit products, it is four fibres. At the other end of the QSFP28, that plugs into the platform, sits a CAUI-4 4x25-gigabit electrical interface (see diagram above).
“The key thing is the CAUI-4 interface; this is what makes it all work," says Theodoras.
Inside the MicroMux, signals are converted between the optical and electrical domains while a gearbox IC translates between 10- or 40-gigabit signals and the CAUI-4 format.
Theodoras stresses that the 10-gigabit inputs are not the old 100 Gigabit Ethernet 10x10 MSA but independent 10 Gigabit Ethernet streams. "They can come from different routers, different ports and different timing domains," he says. "It is no different than if you had 10, 10 Gigabit Ethernet ports on the front face plate."
Using the pluggables, a 5-terabit CloudConnect configuration can support up to 520, 10 Gigabit Ethernet ports, according to ADVA Optical Networking.
The first products will be shipped in the third quarter to preferred customers that help in its development while the products will be generally available at the year-end.
ADVA Optical Networking unveiled the MicroMux at OFC 2016, held in Anaheim, California in March. ADVA also used the show to detail its Open Optical Line System demonstration with switch vendor, Arista Networks.
Two years after Microsoft first talked about the [Open Optical Line System] concept at OFC, here we are today fully supporting it
Open Optical Line System
The Open Optical Line System is a concept being promoted by the Internet content providers to afford them greater control of their optical networking requirements.
Data centre players typically update their servers and top-of-rack switches every three years yet the optical transport functions such as the amplifiers, multiplexers and ROADMs have an upgrade cycle closer to 15 years.
“When the transponding function is stuck in with something that is replaced every 15 years and they want to replace it every three years, there is a mismatch,” says Theodoras.
Data centre interconnect line cards can be replaced more frequently with newer cards while retaining the chassis. And the CloudConnect product is also designed such that its optical line shelf can take external wavelengths from other products by supporting the Open Optical Line System. This adds flexibility and is done in a way that matches the work practices of the data centre players.
“The key part of the Open Optical Line System is the software,” says Theodoras. “The software lets that optical line shelf be its own separate node; an individual network element.”
The data centre operator can then manage the standalone CloudConnect Open Optical Line System product. Such a product can take coloured wavelength inputs and even provide feedback with the source platform, so that the wavelength is tuned to the correct channel. “It’s an orchestration and a management level thing,” says Theodoras.
Arista recently added a coherent line card to its 7500 spine switch family.
The card supports six CFP2-ACOs that have a reach of up to 2,000km, sufficient for most data centre interconnect applications, says Theodoras. The 7500 also supports the layer-two MACsec security protocol. However, it does not support flexible modulation formats. The CloudConnect does, supporting 100-, 150- and 200-gigabit formats. CloudConnect also has a 3,000km reach.
Source: ADVA Optical Networking
In the Open Optical Line System demonstration, ADVA Optical Networking squeezed the Arista 100-gigabit wavelength into a narrower 37.5GHz channel, sandwiched between two 100 gigabit wavelengths from legacy equipment and two 200 gigabit (PM-16QAM) wavelengths from the CloudConnect Quadplex card. All five wavelengths were sent over a 2,000km link.
Implementing the Open Optical Line System expands a data centre manager’s options. A coherent card can be added to the Arista 7500 and wavelengths sent directly using the CFP2-ACOs, or wavelengths can be sent over more demanding links, or ones that requires greater spectral efficiency, by using the CloudConnect. The 7500 chassis could also be used solely for switching and its traffic routed to the CloudConnect platform for off-site transmission.
Spectral efficiency is important for the large-scale data centre players. “The data centre interconnect guys are fibre-poor; they typically only have a single fibre pair going around the country and that is their network,” says Theodoras.
The joint demo shows that the Open Optical Line System concept works, he says: “Two years after Microsoft first talked about the concept at OFC, here we are today fully supporting it.”
Ciena enhances its 6500 packet-optical transport family
"The 6500 T-Series is a big deal as Ciena can offer two different systems depending on what the customer is looking for," says Andrew Schmitt, founder and principal analyst of market research firm, Cignal AI.
Helen XenosIf customers want straightforward transport and the ability to reach a number of different distances, there is the existing 6500 S-series, says Schmitt. The T-series is a system specifically for metro-regional networks that can accommodate multiple traffic types – OTN or packet.
"It has very high density for a packet-optical system and offers pay-as-you-grow with CFP2-ACO [coherent pluggable] modules," says Schmitt.
Ciena says the T-series has been developed to address new connectivity requirements service providers face. Content is being shifted to the metro to improve the quality of experience for end users and reduce capacity on backbone networks. Such user consumption of content is one factor accounting for the strong annual 40 percent growth in metro traffic.
According to Ciena, service providers have to deploy multiple overlays of network elements to scale capacity, including at the photonic switch layer, because they need more than 8-degree reconfigurable optical add/ drop multiplexers (ROADMs).
Operators are looking for a next-generation platform for these very high-capacity switching locations to efficiently distribute content
But overlays add complexity to the metro network and slow the turn-up times of services, says Helen Xenos, director, product and technology marketing at Ciena: "Operators are looking for a next-generation platform for these very high-capacity switching locations to efficiently distribute content."
U.S. service provider Verizon is the first to announce the adoption of the 6500 T-series to modernise its metro and is now deploying the platform. "Verizon is dealing with a heterogeneous network in the metro with many competing requirements," says Schmitt. "They don’t have the luxury of starting over or specialising like some of the hyper-scale transport architectures."
The T-series, once deployed, will handle the evolving requirements of Verizon's network. "Sure, it comes with additional costs compared with bare-bones transport but my conversation with folks at Verizon would indicate flexibility is worth the price," says Schmitt.
Ciena has over 500 customers in 50 countries for its existing 6500 S-series. Customers include 18 of the top 25 communications service providers and three of the top five content providers.
Xenos says an increasing number of service providers are interested in its latest platform. The T-series is part of six request-for-proposals (RFPs) and is being evaluated in several service providers' labs. The 6500 T-series will be generally available this month.
6500 T-series
The existing 6500 S-series family comprises four platforms, from the 2 rack-unit (RU) 6500-D2 chassis to the 22RU 6500-S32 that supports Ethernet, time-division multiplexed traffic and wavelength division multiplexing, and 3.2 terabit-per-second (Tbps) packet/ Optical Transport Network (OTN) switching.
The two T-series platforms are the half rack 6500-12T and the full rack 6500-24T. The cards have been upgraded from 100-gigabit switching per slot to 500-gigabit per slot.
The 6500-T12 has 12 service slots which house either service interfaces or photonic modules. There are also 2 control modules. Shown at the base of the chassis are four 500 Gig switching modules. Source: Ciena
The 500 gigabit switching per slot means the 6500-12T supports 6 terabits of switching capacity while the -24T will support 12 terabits by year end. The platforms have been tested and will support 1 terabit per slot, such that the -24T will deliver the full 24 terabit. Over 100 terabit of switching capacity will be possible in a multiple-chassis configuration, managed as a single switching node.
The latest platforms can use Ciena's existing coherent line cards that support two 100 gigabit wavelengths. The T-Series also supports a 500-gigabit coherent line card with five CFP2-ACOs coupled with Ciena's WaveLogic 3 Nano DSP-ASIC.
"We will support higher-capacity wavelengths in a muxponder configuration using our existing S-series," says Xenos. "But for switching applications, switching lower-speed traffic across the shelf onto a very high-capacity wavelength, this is something that the T-series would be used for."
The T-series also adds a denser, larger-degree ROADM, from an existing 6500 S-series 8-degree to a 16-degree flexible grid, colourless, directionless and contentionless (CDC) design. Xenos says the ROADM design is also more compact such that the line amplifiers fit on the same card.
"The requirements of this platform is that it has full integration of layer 0, layer 1 and layer 2 functions," says Xenos.
The 6500 T-series supports open application programming interfaces (APIs) and is being incorporated as part of Ciena's Emulation Cloud. The Emulation Cloud enabling customers to test software on simulated network configurations without requiring 6500 hardware and is being demonstrated at OFC 2016.
The 6500 is also being integrated as part of Ciena's Blue Planet orchestration and management architecture.
OFC 2016: a sample of the technical paper highlights
Here is a small sample of the technical paper highlights being presented at the conference.
Doubling core network capacity
Microsoft has conducted a study measuring the performance of its North American core backbone network to determine how the use of bandwidth-variable transceivers (BVTs) could boost capacity.
The highest capacity modulation scheme suited for each link from the choice of polarisation-multiplexed, quadrature phase-shift keying (PM-QPSK), polarisation-multiplexed, 8 quadrature amplitude modulation (PM-8QAM) and PM-16QAM can then be used.
By measuring the signal (Q-factor) for all its PM-QPSK based 100 gigabit links, Microsoft's study found that network capacity could be increased by 70 percent using BVTs. Equally, having the ability to increase capacity in 25-gigabit increments would increase capacity by a further 16 percent while a finer resolution of 1-gigabit would add an extra 13 percent.
Microsoft says such tuning of links need not be done in real time but rather when a link is commissioned or undergoing maintenance.
[paper M2J.2]
Architecting a new metro
How can operators redesign their metro network to enable rapid service innovation? This is the subject of a joint paper from AT&T, the Open Networking Lab and Stanford University. The work is part of a programme dubbed CORD to redesign the central office as a data centre using commodity hardware and open software to enable the rapid scaling of services. In particular, OpenFlow-enabled white boxes, the Open Network Operating System (ONOS) - a software-defined networking (SDN) operating system, and network control and management applications are used.
As part of CORD, three legacy telecom devices - optical line termination (OLT), customer premises equipment (CPE), and broadband network gateways (BNG) - have been virtualised and implemented on servers.
The paper details how a single SDN control plane based on ONOS is used to create a converged packet-optical metro network and how its support for bandwidth on-demand and automatic restoration at the optical level is used for enterprise connectivity and video distribution services.
The paper also discusses how the metro architecture supports 'disaggregated' reconfigurable optical add/ drop multiplexers (ROADMs). By disaggregating a chassis-based ROADM into commodity components, an operator can size its infrastructure as required and grow it with demand, the paper says.
[paper Th1A.7]
400 gigabit single-carrier transmission
Nokia Bell Labs reports work on 400 gigabit-per-second (Gbps) single-carrier optical transmission over submarine distances. The attraction of adopting 400 gigabit single-carrier transmission as that it is the most efficient way to reduce the cost-per-bit of optical transmission systems.
The Bell Labs' paper reviews state-of-the-art 400 gigabit single-channel transmissions over 6,000km and greater distances, and discusses the tradeoffs between such variables as symbol rate, modulation and forward error correction (FEC) schemes.
400Gbps single-carrier submarine transmission is likely in the next few years
PM-16QAM is proposed as a promising modulation scheme to achieve beyond 6,000km distances and a spectral efficiency exceeding 5b/s/Hz. But this requires a symbol rate of greater than 60 gigabaud to accommodate the 20 percent overhead FEC. Pulse-shaping at the transmitter is also used.
Exploring the receiver performance with the varying symbol rate/ FEC overhead, Bell Labs reports that the best tradeoff between coding gain and implementation penalties is 64 gigabaud and 27.3% overhead. It concludes that single-carrier 400Gbps submarine transmission is likely in the next few years.
[paper Th1B.4]
Silicon modulator for CFP2-ACOs
Cisco has developed a compact flip-chip assembly that combines a silicon photonics modulator and a silicon germanium BiCMOS Mach-Zehnder modulator driver. Such an assembly forms the basis for low-cost advanced coherent optical transceivers such as the CFP2-ACO.
Cisco has demonstrated the assembly operating at 128.7Gbps using PM-QPSK and 257.3Gbps using PM-16QAM. Cisco believes this is the first demonstration of transmission at 257.3Gbps using PM-16QAM over 1,200km of standard single-mode fibre using a silicon photonics-based device.
The modulator has also been demonstrated operating at 321.4Gbps using PM-16QAM transmission and a 20 percent FEC overhead, the highest bit rate yet achieved using a silicon-photonics based transmitter, claims Cisco.
Cisco is already using CFP2-ACO modules as part of its NCS 1002 data centre interconnect platform that implement PM-16QAM and deliver 250 gigabit due to the use of a higher baud rate than the 32 gigabaud used for existing 100-gigabit coherent systems.
[paper Th1F.2]
Flexible Ethernet to exploit line-side efficiencies
Given how the optical network network is starting to use adaptive-rate interfaces, a paper from Google asks how the client side can benefit from such line-side flexibility.
The paper points out that traditional DWDM transport equipment typically multiplexes lower-rate client ports but that this doesn't apply to network operators that manage their own data centres. Here, traffic is exclusively packet-based from IP routers and typically matches the line rate. This is why data centre interconnect platforms have become popular as they require limited grooming capability.
Google highlights how Flexible Ethernet (FlexE), for which the Optical Internetworking Forum has just defined an Implementation Agreement for, combined with data centre interconnect equipment is an extremely effective combination.
FlexE supports Ethernet MAC rates independent of the Ethernet physical layer rate being used. Google shows examples of how using FlexE, sub client rates can match the line-side rate as well as how multiple client ports can support a higher speed router logical port.
The paper concludes that combining FlexE with data centre interconnect results in a low cost, low power, compact design that will enable Internet content providers to scale their networks.
[paper W4G.4]
OIF document aims to spur line-side innovation
The CFP2-ACO. Source: OIF
The pluggable CFP2-ACO houses the coherent optics, known as the analogue front end. The components include the tuneable lasers, modulation, coherent receiver, and the associated electronics - the drivers and the trans-impedance amplifier. The Implementation Agreement also includes the CFP2-ACO's high-speed electrical interface connecting the optics to the coherent DSP chip that sits on the line card.
One historical issue involving the design of innovative optical components into systems has been their long development time, says Ian Betty of Ciena, and OIF board member and editor of the CFP2-ACO Implementation Agreement. The lengthy development time made it risky for systems vendors to adopt such components as part of their optical transport designs. Now, with the CFP2-ACO, much of that risk is removed; system vendors can choose from a range of CFP2-ACO suppliers based on the module's performance and price.
Implementation Agreement
Much of the two-year effort developing the Implementation Agreement involved defining the management interface to the optical module. "This is different from our historical management interfaces," says Betty. "This is much more bare metal control of components."
For 7x5-inch and 4x5-inch MSA transponders, the management interface is focused on system-level parameters, whereas for the CFP2-ACO, lower-level optical parameters are accessible given the module's analogue transmission and receive signals.
"A lot of the management is to interrogate information about power levels, or adjusting transfer functions with pre-emphasis, or adjusting drive levels on drivers internal to the device, or asking for information: 'Have you received my RF signal?'," says Betty. "It is very much a lower-level interface because you have separated between the DSP and the optical interface."
The Implementation Agreement's definitions for the CFP2-ACO are also deliberately abstract. The optical technology used is not stated, nor is the module's data rate. "The module has no information associated with the system level - if it is 16-QAM or QPSK [modulation] or what the dispersion is," says Betty.
This is a strength, he says, as it makes the module independent of a data rate and gives it a larger market because any coherent ASIC can make use of this analogue front end. "It lets the optics guys innovate, which is what they are good at," says Betty.
Innovation
The CFP2-ACO is starting to be adopted in a variety of platforms. Arista Networks has added a CFP2-ACO line card to its 7500 data centre switches while several optical transport vendors are using the module for their data centre interconnect platforms.
One obvious way optical designers can innovate is by adding flexible modulation formats to the CFP2-ACO. Coriant's Groove G30 data centre interconnect platform uses CFP2-ACOs that support polarisation-multiplexed, quadrature phase-shift keying (PM-QPSK), polarisation-multiplexed, 8-state quadrature amplitude modulation (PM-8QAM) and PM-16QAM, delivering 100, 150 and 200 gigabit-per-second transmission, respectively. Coriant says the CFP2-ACOs it uses are silicon photonics and indium phosphide based.
Cisco Systems uses CFP2-ACO modules for its first data centre interconnect product, the NCS 1002. The system can use a CFP2-ACO with a higher baud rate to deliver 250 gigabit-per-second using a single carrier and PM-16QAM.
Ian BettyThe CFP2-ACO enables a much higher density line-side solution than other available form factors. The Groove G30, for example, fits eight such modules on one rack-unit line card. "That is the key enabler that -ACOs give," says Betty.
And being agnostic to a particular DSP, the CFP2-ACO enlarges the total addressable market. Betty hopes that by being able to sell the CFP2-ACO to multiple systems vendors, the line-side optical module players can drive down cost.
Roadmap
Betty says that the CFP2-ACO may offer the best route to greater overall line side capacity rather than moving to a smaller form factor module in future. He points out that in the last decade, the power consumption of the optics has gone down from some 16W to 12W. He does not foresee the power consumption coming down further to the 6W region that would be needed to enable a CFP4-ACO. "The size [of the CFP4] with all the technology available is very doable," says Betty. "But there is not an obvious way to make it [the optics] 6W."
The key issue is the analogue interface which determines what baud rate and what modulation or level of constellation can be put through a module. "The easiest way to lump all that together is with an implementation penalty for the optical front end," says Betty. "If you make the module smaller, you might have a higher implementation penalty, and with this penalty, you might not be able to put a higher constellation through it."
In other words, there are design trade-offs: the data rates supported by the CFP2 modules may achieve a higher overall line-side rate than more, smaller modules, each supporting a lower maximum data rate due to a higher implementation penalty.
"What gets you the ultimate maximum density of data rate through a given volume?" says Betty. "It is not necessarily obvious that making it smaller is better."
Could a CFP2-ACO support 32-QAM and 64-QAM? "The technical answer is what is the implementation penalty of the module?" says Betty. This is something that the industry will answer in time.
"This isn't the same as client optics where there is a spec, you do the spec and there are no brownie points for doing better than the spec, so all you can compete on is cost," says Betty. "Here, you can take your optical innovation and compete on cost, and you can also compete by having lower implementation penalties."