Infinera buying Coriant will bring welcome consolidation
Infinera is to purchase privately-held Coriant for $430 million. The deal will effectively double Infinera’s revenues, add 100 new customers and expand the systems vendor’s product portfolio.
Infinera's CEO, Tom FallonBut industry analysts, while welcoming the consolidation among optical systems suppliers, highlight the challenges Infinera faces making the Coriant acquisition a success.
“The low price reflects that this isn't the best asset on the market,” says Sterling Perrin, principal analyst, optical networking and transport at Heavy Reading. “They are buying $1 of revenue for 50 cents; the price reflects the challenges.”
Benefits
According to Perrin, there are still too many vendors facing "brutal price pressures" despite the optical industry being mature. Removing one vendor that has been cutting prices to win business is good news for the rest.
For Infinera, the acquisition of Coriant promises three main benefits, as outlined by its CEO, Tom Fallon, during a briefing addressing the acquisition.
The first is expanding its vertically-integrated business model across a wider portfolio of products. Infinera develops its own optical technology: its indium-phosphide photonic integrated circuits (PICs) and accompanying coherent DSPs that power its platforms. Having its own technology differentiates the optical performance of its platforms and helps it achieve leading gross margins of over 40 percent, said Fallon.
Exploiting the vertical integration model will be a central part of the Coriant acquisition. Indeed, the company mentioned vertical integration 21 times in as many minutes during its briefing outlining the deal. Infinera expects to deliver industry-leading growth and operating margins once it exploits the benefits of vertical integration across an expanded portfolio of platforms, said Fallon.
Having a seat at the table with the largest global service providers to strategise about where their business is going will be invaluable
Buying Coriant also gives Infinera much-needed scale. Not only will Infinera double its revenues - Coriant’s revenues were about $750 million in 2017 while Infinera’s were $741 million for the same period - but it will expand its customer base including key tier-one service providers and webscale players. According to Fallon, the newly combined company will include nine of the top 10 global tier-one service providers and the six leading global internet content providers.
Infinera admits it has struggled to break into the tier-one operators and points out that trying to enter is an expensive and time-consuming process, estimated at between $10 million to $20 million each time. “[Now, with Coriant,] having a seat at the table with the largest global service providers to strategise about where their business is going will be invaluable,” said Fallon.
Sterling Perrin of Heavy Reading The third benefit Infinera gains is an expanded product portfolio. Coriant has expertise in layer 3 networking, in the metro core with its mTera universal transport platform as well as SDN orchestration and white box technologies. Heavy Reading’s Perrin says Coriant has started development of a layer-3 router white box for edge applications.
Combining the two companies also results in a leading player in data centre interconnect.
“Coriant expands our portfolio, particularly in packet and automation where significant network investment is expected over the next decade,” said Fallon. The deal is happening at the right time, he said, as operators ramp spending as they undertake network transformation.
Infinera will pay $230 million in cash - $150 million up front and the rest in increments - and a further $200 million in shares for Coriant. The company expects to achieve cost savings of $250 million between 2019 and 2021 by combining the two firms, $100 million in 2019 alone. The deal is expected to close in the third quarter of 2018.
If a company is going to put that integrated product into their network, it’s a full-blown RFP process which Infinera may or may not win
Challenges
Industry analysts, while seeing positives for Infinera, have concerns regarding the deal.
A much-needed consolidation of weaker vendors is how George Notter, an analyst at the investment bank, Jefferies, describes the deal. For Infinera, however, continuing as before was not an option. Heavy Reading’s Perrin agrees: ”Infinera has been under a lot of pressure; their core business of long-haul has slowed.”
The deal brings benefits to Infinera: scale, complementary product sets, and the promise of being able to invest more in R&D to benefit its PIC technology, says Notter in a research note.
Gaining customers is also a key positive. “Infinera is really excited about getting the new set of customers and that is what they are paying for,” says Vladimir Kozlov, CEO of LightCounting Market Research. “However, these customers were gained by pricing products at steep discounts.”
What is vital for Infinera is that it delivers its upcoming 2.4-terabit Infinite Capacity Engine 5 (ICE5) optical engine on time. The ICE5 is expected to ship in early 2019. In parallel, Infinera is developing its ICE6 due two years later. Infinera is developing two generations of ICE designs in parallel after being late to market with its current 1.2-terabit optical engine.
Infinera is really excited about getting the new set of customers and that is what they are paying for
But even if the ICE5 is delivered on time, upgrading Coriant's platforms will be a major undertaking. “It sounds like they are going to fit their optical engines in all of Coriant’s gear; I don’t see how that is going to happen anytime quickly,” says Perrin.
Customers bought Coriant's equipment for a reason. Once upgraded with Infinera’s PICs, these will be new products that have to undergo extensive lab testing and full evaluations.
Perrin questions how moving customers off legacy platforms to the new will not result in the service providers triggering a new request-for-proposal (RFP). “If a company is going to put that integrated product into their network, it’s a full-blown RFP process which Infinera may or may not win,” says Perrin. “Infinera talked a lot about the benefits of vertical integration but they didn’t really address the challenges and the specific steps they would take to make that work.”
LightCounting's Vladimir KozlovLightCounting’s Kozlov also questions how this will work.
“The story about vertical integration and scaling up PIC production is compelling, but how will they support Coriant products with the PIC?” he says. “Will they start making pluggable modules internally? Will Coriant’s customers be willing to move away from the pluggables and get locked into Infinera’s PICs? Do they know something that we don’t?”
While Infinera is a top five optical platform supplier globally it hasn’t dominated the market with its PIC technologies, says Perrin. “Even if they technically pull off the vertical integration with the Coriant products, how much is that going to win business for them?” he says. “It is one architecture in a mix that has largely gone to pluggables.”
Transmode
Infinera already has experience acquiring a systems vendor when it bought in 2015 metro-access player, Transmode. Strategically, this was a very solid acquisition, says Perrin, but the jury is still out as to its success.
“The integration, making it work, how Transmode has performed within Infinera hasn’t gone as well as they wanted,” says Perrin. “That said, there are some good opportunities going forward for the Transmode group.”
Infinera also had planned to integrate its PIC technology within Transmode’s products but it didn't make economic sense for the metro market. There may also have been pushback from customers that liked the Transmode products, says Perrin: “With Coriant it looks like they really are going to force the vertical integration.”
Infinera acknowledges the challenges ahead and the importance of overcoming them if it is to secure its future.
“Given the comparable sizes of each company’s revenues and workforce, we recognise that integration will be challenging and is vital for our ultimate success,” said Fallon.
Ciena goes stackable with 8180 'white box' and 6500 RLS
Ciena has unveiled two products - the 8180 coherent networking platform and the 6500 reconfigurable line system - that target cable and cellular operators that are deploying fibre deep in their networks, closer to subscribers.
The 6500 line system is also aimed at the data centre interconnect market given how the webscale players are experiencing a near-doubling of traffic each year.
Source: Ciena
The cable industry is moving to a distributed access architecture (DAA) that brings fibre closer to the network’s edge and splits part of the functionality of the cable modem termination system (CMTS) - the remote PHY - closer to end users. The cable operators are deploying fibre to boost the data rates they can offer homes and businesses.
Both Ciena’s 8180 modular switch and the 6500 reconfigurable line system are suited to the cable network. The 8180 is used to link the master headend with primary and secondary hub sites where aggregated traffic is collected from the digital nodes (see network diagram). The 8180 platforms will use the modular 6500 line system to carry the dense wavelength-division multiplexed (DWDM) traffic.
“The [cable] folks that are modernising the access network are not used to managing optical networking,” says Helen Xenos, senior director, portfolio marketing at Ciena (pictured). “They are looking for simple platforms, aggregating all the connections that are coming in from the access.”
The 8180 can play a similar role for wireless operators, using DWDM to carry aggregated traffic for 4G and 5G networks.
Ciena says the 6500 optical line system will also serve the data centre interconnect market, complementing the WaveServer Ai, Ciena’s second-generation 1RU modular platform that has 2.4 terabits of client-side interfaces and 2.4 terabits of coherent capacity.
With the 8180, you are only using the capacity on the fibre that you have traffic for
“They [the webscale players] are looking for as many efficiencies as they can get from the platforms they deploy,” says Xenos. “The 6500 reconfigurable line system gives them the flexibility they need - a colourless, directionless, contentionless [reconfigurable optical add-drop multiplexer] and a flexible grid that extends to the L-band.”
A research note from analyst house, Jefferies, published after the recent OFC show where Ciena announced the platforms, noted that in many cable networks, 6-strand fibre is used: two fibre pairs allocated for business services and one for residential. Adding the L-band to the existing C-band effectively doubles the capacity of each fibre pair, it noted.
The 8180
Ciena’s 8180 is a modular packet switch that includes coherent optics. The 8180 is similar in concept to the Voyager and Cassini white boxes developed by the Telecom Infra Project. However, the 8180 is a two-rack-unit (2RU) 6.4-terabit switch compared to the 1RU, 2-terabit Voyager and the 1.5RU 3.2-terabit Cassini. The 8180 also uses Ciena’s own 400-gigabit coherent DSP, the WaveLogic Ai, rather than merchant coherent DSP chips.
The platform comprises 32 QSFP+/ QSFP28 client-side ports, a 6.4-terabit switch chip and four replaceable modules or ‘sleds’, each capable of accommodating 800 gigabits of capacity. The options include an initial 400-gigabit line-side coherent interface (a sled with two coherent WaveLogic Ai DSPs will follow), an 8x100-gigabit QSFP28 sled, a 2x400-gigabit sled and also the option for an 800-gigabit module once they become available.
Source: Ciena
Using all four sleds as client-side options, the 8180 becomes a 6.4-terabit Ethernet switch. Using only coherent sleds instead, the packet-optical platform has a 1.6-terabit line-side capacity. And because there is a powerful switch chip integrated, the input ports can be over-subscribed.“With the 8180, you are only using the capacity on the fibre that you have traffic for,” says Xenos.
6500 line system
The 6500 reconfigurable line system is also a modular design. Aimed at the cable, wireless, and data centre interconnect markets, only a subset of Ciena’s existing optical line systems features is used.
“The 6500 software has a lot of capabilities that the content providers are not using,” says Xenos. “They just want to use it as a photonic layer.”
There are three 6500 reconfigurable line system platform sizes: 1RU, 2RU and 4RU. The chassis can be stacked and managed as one unit. Card options that fit within the chassis include amplifiers and reconfigurable optical add-drop multiplexers (ROADMs).
The amplifier options area dual-line Erbium-doped fibre amplifiercard that includes an integrated bi-directional optical time-domain reflectometer (OTDR) used to characterise the fibre. There is also a half-line-width RAMAN amplifier card. The line system will support the C and L bands, as mentioned.
The reconfigurable line system also has ROADM cards: a 1x12 wavelength-selective switch (WSS) with integrated amplifier, a colourless 16-channel add-drop that support channels of any size (flexible grid), and a full-width card 1x32 WSS. “The 1x32 would be used for colourless, directionless and directionless [ROADM] configurations,” says Xenos.
The 6500 reconfigurable line system also supports open application porgramming interfaces (APIs) for telemetry, with a user able to program the platform to define the data streamed.“The platform can also be provisioned via REST APIs; something a content provider will do,” she says.
Ciena is a member of the OpenROADM multi-source agreement and was involved in last year’s AT&T OpenROADM trial with its 6500 Converged Packet Optical Transport (POTS) platform.
Will the 6500 reconfigurable line system be OpenROADM-compliant?
“This card [and chassis form factor] could be used for OpenROADM if AT&T preferred this platform to the other [6500 Converged POTS] one,” says Xenos. “You also have to design the hardware to meet the specifications for OpenROADM.”
Ciena expects both platforms to be available by year-end. The 6500 reconfigurable line system will be in customer trials at the end of this quarter while the 8180 will be trialed by the end of the third quarter.
Juniper Networks opens up the optical line system
Juniper Networks has responded to the demands of the large-scale data centre players with an open optical line system architecture.
Donyel Jones-WilliamsThe system vendor has created software external to its switch, IP router and optical transport platforms that centrally controls the optical layer.
Juniper has also announced a reconfigurable optical add-drop multiplexer (ROADM) - the TCX1000 - that is Lumentum’s own white box ROADM design. Juniper will offer the Lumentum white box as its own, part of its optical product portfolio.
The open line system architecture, including the TCX1000, is also being pitched to communications service providers that want an optical line system and prefer to deal with a single vendor.
“Juniper plans to address the optical layer with a combination of software and open hardware in the common optical layer,” says Andrew Schmitt, founder and lead analyst at Cignal AI. “This is the solution it will bring to customers rather than partnering with an optical vendor, which Juniper has tried several times without great success.”
Open line systems
An optical line system comprises terminal and transmission equipment and network management software. The terminal equipment refers to coherent optics hosted on platforms, while line elements such as filters, optical amplifiers and ROADMs make up the transmission equipment. Traditionally, a single vendor has provided all these elements with the network management software embedded within the vendor’s platforms.
An open optical line system refers to line equipment and the network management system from a vendor such as Nokia, Infinera or Ciena that allows the attachment of independent terminal equipment. An example would be the Telecom Infra Project’s Voyager box linked to a Nokia line system, says Schmitt.
The open line system can also be implemented as a disaggregated design. Here, says Schmitt, the control software would be acquired from a vendor such as Juniper, Fujitsu, or Ciena with the customer buying open ROADMs, amplifiers and filters from various vendors before connecting them. Open software interfaces are used to communicate with these components. And true to an open line system, any terminal equipment can be connected.
The advantage of an open disaggregated optical line system is that elements can be bought from various sources to avoid vendor lock-in. It also allows the best components to be acquired and upgraded as needed.
Meanwhile, disaggregating the management and control software from the optical line system and equipment appeals to the way the internet content providers architect and manage their large-scale data centres. This is what Juniper’s proNX Optical Director platform enables, the second part of its open line system announcement.
Juniper believes its design is an industry first in how it separates the control plane from the optical hardware.
“We have taken the concept of disaggregation and software-defined networking to separate the control plane out of the hardware,” says Donyel Jones-Williams, director of product marketing management at Juniper Networks. “Our control plane is no longer tied to physical hardware.”
Having an open line system supplied by one vendor gets you 90% of the way there
Disaggregated control benefits the optimisation of the open line system, and enables flexible updates without disrupting the service.
Cignal AI’s Schmitt says that the cloud and co-location players are already using open line systems just not disaggregated ones.
“Having an open line system supplied by one vendor gets you 90% of the way there,” says Schmitt. For him, a key question is what problem is being solved by taking this one step further and disaggregating the hardware.
Schmitt’s view is that an operator introduces a lot of complexity into the network for the marginal benefit of picking hardware suppliers independently. “And realistically they are still single-sourcing the software from a vendor like Juniper or Ciena,” says Schmitt.
Juniper now can offer an open line system, and if a customer wants a disaggregated one, it can build it. “I don’t think users will choose to do that,” says Schmitt. “But Juniper is in a great position to sell the right open line system technology to its customer base and this announcement is interesting and important because Juniper is clearly stating this is the path it plans to take.”
TCX1000 and proNX
Juniper’s open optical line system announcement is the latest development in its optical strategy since it acquired optical transport firm, BTI Systems, in 2016.
BTI’s acquisition provided Juniper with a line system for 100-gigabit transport. “The filters and ROADMs didn’t allow the system to scale to 200-gigabit and 400-gigabit line rates and to support super-channels and flexgrid,” says Jones-Williams.
With the TCX1000, Juniper now has a one-rack-unit 20-degree ROADM that is colourless, directionless and which supports flexgrid to enable 400-gigabit, 600-gigabit and even higher capacity optical channels in future. The TCX1000 supports up to 25.6 terabits-per-second per line.
A customer can also buy the white box ROADM from Lumentum directly, says Juniper. “It gives our customers freedom as to how they want to source their product,” says Jones-Williams.
Competition between vendors is now in the software domain. We no longer believe that there is differentiation in the optical line system hardware
Juniper’s management and control software, the ProNX Optical Director, has been architected using microservices. Microservices offers a way to architect applications using virtualisation technology. Each application is run in isolation based on the service they provide. This allows a service to run and scale independently while application programming interfaces (APIs) enable communication with other services.
Container technology is used to implement microservices. Containers use fewer hardware resources than virtual machines, an alternative approach to server virtualisation.
Source: Juniper Networks.
“It is built for data centre operators,” says Don Frey, principal analyst, routers and transport at the market research firm, Ovum. “Microservices makes the product more modular.”
Juniper believes the competition between vendors is now in the software domain. “We no longer believe that there is differentiation in the optical line system hardware,” says Jones-Williams.
Data centre operators are not concerned about line system interoperability, they are just trying to remove the blade lock-in so they can get the latest technology.
Market demands
Most links between data centres are point-to-point networks yet despite that, the internet content providers are interested in ROADMs, says Juniper. What they want is to simplify network design using the ROADM’s colourless and flexible grid attributes. A directionless ROADM is only needed for complex hub sites that require flexibility in moving wavelengths through a mesh network.
The strategy of the large-scale data centre operators is to split the optical system between an open line system and purpose-built blades. The split allows them to upgrade to the best blades or pluggable optics while leaving the core untouched. “The concept is similar to the open submarine cables as the speed of innovation in core systems is not the same as the line optics,” says Frey. “Data centre operators are not concerned about line system interoperability, they are just trying to remove the blade lock-in so they can get the latest technology.”
Juniper says there is also interest from communications service providers in the ROADM as part of their embrace of open initiatives such as the Open ROADM MSA. Frey says AT&T will make its first deployment of the Open ROADM before the year-end or in early 2018.
“There are a lot of synergies in terms of what we have announced and things like Open ROADM,” says Jones-Williams. “But we know that there are customers out there that just want a line system and they do not care if it is open or not.”
Juniper is already working with customers with its open line system as part of the development of its proNX software.
The branded ROADM and the proNX Optical Director will be generally available in early 2018.
Has coherent optical transmission run its course?
Feature: Coherent's future
Three optical systems vendors share their thoughts about coherent technology and the scope for further improvement as they look two generations ahead to symbol rates approaching 100 gigabaud
Optical transmission using coherent detection has made huge strides in the last decade. The latest coherent technology with transmitter-based digital signal processing delivers 25x the capacity-reach of 10-gigabit wavelengths using direct-detection, according to Infinera.
Since early 2016, the optical systems vendors Infinera, Ciena and Nokia have all announced new coherent digital signal processor (DSP) designs. Each new generation of coherent DSP improves the capacity that can be transmitted over an optical link. But given the effectiveness of the latest coherent systems, has most of the benefits already been achieved?
Source: Infinera
“It is getting harder and harder,” admits Kim Roberts, vice president, WaveLogic science at Ciena. “Unlike 10 years ago, there are no factors of 10 available for improvement.”
Non-linear Shannon limit
It is the non-linear Shannon limit that defines how much information can be sent across a fibre, a function of the optical signal-to-noise ratio.
Kim Roberts of CienaThe limit is based on the work of famed mathematician and information theorist, Claude Shannon. Shannon's work was based on a linear communication channel with added Gaussian noise. Optical transport over a fibre is a more complex channel but the same Shannon bound applies, although assumptions for the non-linearities in the fibre must be made.
Roberts stresses that despite much work, the industry still hasn't figured out just what the upper limit is over a fibre for a given optical signal-to-noise ratio.
It is getting harder and harder. Unlike 10 years ago, there are no factors of 10 available for improvement.
"There are papers that show that with this method and this method, you can do this much," says Roberts. "And there are other papers that show that as the power goes up, there is no theoretical limit until you melt the fibre."
These are theoretical things, he says, but the key is that the headroom available remains unknown. What is known is that the theoretical limit remains well ahead of practical systems. Accordingly, systems performance can be improved using a combination of techniques and protocols coupled with advances in electro-optics.
Design goals
A key goal when designing a new optical transmission system is to increase the data sent for a given cost i.e. decrease the cost-per-bit. This is an ongoing requirement as the service providers contend with ever growing network traffic.
Another challenge facing engineers is meeting the demanding power, density and thermal constraints of their next-generation optical transport system designs.
One way to reduce the cost-per-bit is to up the symbol rate to increase the data sent over a wavelength. Traditional 100-gigabit and 200-gigabit dense wavelength-division multiplexing (DWDM) systems use 32-35 gigabaud (GBaud). The latest coherent DSPs already support more than one baud rate: Nokia’s PSE-2s coherent DSP supports 33Gbaud or 45Gbaud while Ciena’s WaveLogic Ai chipset supports 35Gbaud or 56Gbaud.
Having a choice of baud rates coupled with the various modulation scheme options means the same number of bits can be sent over a range of optical reaches. The more complex the modulation scheme, the closer the points are in a constellation and the harder it is to correctly detect the data at the receiver in the presence of noise. Accordingly, using the combination of a simpler modulation scheme and a higher baud rate allows the same data to be sent further.
Capacity-reach is what matters: how much capacity you can extract for a given reach
Nokia's 1.4-billion transistor PSE-2s supports two 200 gigabit-per-second (Gbps) formats: polarisation-multiplexing, 16-ary quadrature amplitude modulation (PM-16QAM) at 33Gbaud, or using PM-8QAM at 45Gbaud. The 200-gigabit wavelength has an optical reach of some 800km using 16-QAM at 33Gbaud but this rises to 1,600km when PM-8QAM at 45Gbaud is used. Alternatively, using 45Gbaud and PM-16QAM, more data can be sent: 250 gigabits-per-wavelength over 800km.
Nokia's Randy EisenachCoherent systems designers are not stopping there. “The next higher baud rate the industry is targeting is 61-68 Gbaud,” says Randy Eisenach, senior product marketing manager, optical networks at Nokia.
Operating at the higher gigabaud range - Infinera talks of 65-70Gbaud - a single transmitter-receiver pair sends twice the amount of data of traditional 32-35Gbaud systems using the same modulation format. But the higher-baud rates require the electro-optics to operate twice as fast. The analogue-to-digital and digital-to-analogue converters of the coherent DSP must sample at twice the baud rate - at least 130 billion samples-per-second. A 65-70Gbaud rate also requires silicon implemented using a more advanced and expensive CMOS process mode - 16nm instead of 28nm. In turn, the optical modulator and drivers need to work well at these higher rates.
“The optical networking industry is well on its way to solving these engineering and component issues in the next year or so,” says Eisenach.
The capacity-per-wavelength also goes up with baud rate. For shorter reach links, 400-600 gigabits-per-wavelength are possible at 65-70Gbaud and, according to Pravin Mahajan, Infinera’s director of product and corporate marketing, power consumption in terms of watts-per-gigabit will improve by some 2.5x.
Pravin Mahajan of InfineraAnd the system vendors are not stopping there: the next baud rate hike after 65-70Gbaud will be in the region of 80-100 Gbaud. The coherent DSPs that will support such data rates will need to be implemented using 7nm CMOS process (see table).
“Capacity-reach is what matters: how much capacity you can extract for a given reach,” says Mahajan. “These successive generations [of faster baud rates] all keep moving that curve upwards.”
DSP features
In addition to the particular baud rates chosen by the vendors for their DSP designs, each includes unique features.
Instead of modulating the data onto a single carrier, Infinera’s FlexCoherent DSP uses multiple Nyquist sub-carriers spread across a channel. The number of subs-carriers varies depending on the link. The benefit of the approach, says Infinera, is that it allows a lowering of the baud rate used which increases the tolerance to non-linear channel impairments experienced during optical transmission.
The FlexCoherent DSP also supports enhanced soft-decision forward-error correction (SD-FEC) including the processing of two channels that need not be contiguous. This is possible as the FlexCoherent DSP is dual-channel which particularly benefits long-haul and subsea applications, claims Infinera. By pairing two channels, the FEC codes can be shared. Pairing a strong channel with a weak one and sharing the codes allows some of the strength of the strong signal to be used to bolster the weaker one, extending its reach or even allowing a more advanced modulation scheme to be used.
Infinera has just announced that by using Nyquist sub-carriers and the FEC gain sharing technologies, its customer, Seaborn Networks, is able delivering 11.8 terabits of capacity over a 10,600km submarine link.
Nokia’s PSE-2s DSP has sufficient processing performance to support two coherent channels. Each channel can implement a different modulation format if desired, or the two can be tightly coupled to form a super-channel. Using 45Gbaud and PM-16QAM, two 250-gigabit channels can be implemented to enable a 500-gigabit muxponder card. The PSE-2s can also implement 400-gigabit wavelength but that is the only format where only one channel can be supported by the PSE-2s.
Ciena’s WaveLogic Ai, meanwhile, uses advanced coding schemes such that it no longer mentions particular modulation schemes but rather a range of line rates in 50-gigabit increments.
Coding schemes with names such as set-partition QPSK, matrix-enhanced PM-BPSK, and 8D-2QAM, have already started to appear in the vendors’ coherent DSPs.
“Vendors use a lot of different terms essentially for the same thing: applying some type of coding to symbols to improve performance,” says Eisenach.
There are two main coding approaches: constellation shaping, also known as probabilistic shaping, and multi-dimensional coding. Combining the two - probabilistic shaping and multi-dimensional coding - promises enhanced performance in the presence of linear and non-linear transmission impairments. These are now detailed.
Probabilistic shaping
The four constellation points of QPSK modulation are equidistant from the origin. With more advanced modulation schemes such as 16-QAM, the constellation points differ in their distance from the origin and hence have different energies. Points in the corners of the constellation, furthest from the origin, have the most energy since a point’s power is the square of the distance from the origin.
Here the origin is at the centre of the square 64-QAM constellation. With probabilistic shaping, more of the points closer to the origin are chosen with the resulting data rate going down. Source: Nokia
Probabilistic shaping uses the inner constellation points more than the outer points, thereby reducing the overall average energy and this improves the signal-to-noise ratio. To understand why, Ciena points out that the symbol error rate at the receiver is dominated by the distance between neighbouring points of the constellation. Reduced the average energy still keeps the distance between the points the same, but when gain is applied to restore the signal’s power levels, the effect is to increase the distance between points. “It means we have better separation between the points, we’ve expanded everything,” says Roberts.
Using probabilistic shaping delivers a maximum 1.53dB of improvement in a linear transmission channel. “That is the theoretical limit,” says Roberts. “In a non-linear world, we get a greater benefit from shaping beyond just shaping the noise.”
Probabilistic shaping also has another benefit: it allows the number of bits sent per symbol to be defined.
Using standard modulation schemes such as 64-QAM with no constellation shaping, 6 bits-per-symbol are sent. Using shaping and being selective in what points are used, fewer bits are sent and they don’t need to be integer values. “I can send 5.7, 5.6, 5.3, even 5.14 bits-per symbol,” says Roberts. “Until I get to 5 bits, and then I have a choice: do I use more shaping or do I start with 32-QAM, which is 5 bits-per-symbol.”
Technology A shows today's coherent DSPs: operating at 30-35Gbaud and delivering 100, 150 and 200Gbps capacities per wavelength. Technology B is Ciena's WaveLogic A. Operating at 56Gbaud, it delivers up to 400Gbps per wavelength in 50Gbps. Technology C will continue this trend. Operating around 70Gbaud, up to 600Gbps per wavelength will be possible in even finer speed increments of 25Gbps. Is this Ciena's next WaveLogic? Source: Ciena
This is very useful as it allows fine control of the data sent such that operators can squeeze just enough data to suit the margins available on a particular fibre link. “You don't have to choose between 100-gigabit and 200-gigabit wavelengths,” says Roberts. "You can use smaller jumps and that sometimes means sending more capacity.”
Three things are needed to fine-tune a link in this way. One is a coherent DSP that can deliver such variable increments on a wavelength using probabilistic shaping. Also needed is a flexible client signalling scheme such as the OIF’s Flexible Ethernet (FlexE) protocol, a protocol mechanism to vary the Ethernet payload for transmission. Lastly, intelligent networking software is required to determine what is happening in the network and the margins available to assess how much data can be squeezed down a link.
Ciena says it has not implemented probabilistic shaping in its latest WaveLogic Ai coherent DSP. But given the Ai will be a family of devices, the technique will feature in upcoming coherent DSPs.
Nokia published a paper at the OFC event held earlier this year showing the use of probabilistic shaping over a transatlantic link. Using probabilistic-shaped 64-QAM (PS-64QAM), a spectral efficiency of 7.46b/s/Hz was achieved over the 5,523km link. This equates to 32 terabits of capacity over the fibre, more than 2.5x the 12 terabits of the existing DWDM system that uses 100Gbps PM-QPSK.
Advanced coding
Multi-dimensional coding is another technique used to improve optical transmission. A 16-QAM constellation is a two-dimensional (2D) representation in one polarisation, says Roberts. But if both polarisations of light are considered as one signal then it becomes a 4D, 256-point (16x16) symbol. This can be further extended by including the symbols in adjacent time slots. This forms an 8D representation.
Non-linear compensation has been an interesting research topic. Nokia continues to investigate the topic and implementation methods but the benefits appear small for most real-world applications
The main two benefits of multi-dimensional coding are better noise performance and significantly better performance in the presence of non-linear impairments.
Nokia’s PSE-2s uses coding for its set-partition QPSK (SP-QPSK). Standard PM-QPSK uses amplitude and phase modulation, resulting in a 4-point constellation. With SP-QPSK, only three of the four constellation points are used for each symbol. A third fewer constellation points means less data is transported but the benefit of SP-QPSK is extended reach due to the greater Euclidean distance between the symbol points created by carefully mapping the sequence of symbols. This results in 2.5dB of extra gain compared to PM-QPSK, for a reach beyond 5,000km.
Using the PSE-2’s 45Gbaud symbol rate, the fewer constellation points of SP-QPSK can be compensated for to achieve the same overall 100Gbps capacity as PM-QPSK at 33Gbaud.
Infinera’s FlexCoherent uses what it calls matrix-enhanced PM-BPSK, a form of averaging that adds 1dB of gain. “Any innovation that adds gain to a link, the margin that you give to operators, is always welcome,” says Mahajan.
Ciena’s WaveLogic 3 Extreme coherent DSP supports the multi-dimension coding scheme 8D-2QAM to improve reach or capacity of long-reach spans.
Such techniques mean vendors have a wealth of available choices available. It is also why Ciena has stopped referring to modulation schemes and talks about its WaveLogic Ai at 35Gbaud supporting 100-250Gbps data rates in 50-gigabit increments while at 56Gbaud, the WaveLogic Ai delivers 100-400Gbps optical channels in 50-gigabit steps.
Probabilistic shaping and multi-dimensional coding are distinct techniques but combining the two means the shaping can be done across dimensions.
Design engineers thus have various techniques to keep improving performance and there are other directions too.
Forward-error correction is about 2dB from the theoretical limit and with improved design Ciena’s Roberts expects 1dB can be reclaimed.
In turn, signal processing techniques could be applied at the transmitter to compensate for expected non-linear effects. “Non-linear compensation has been an interesting research topic,” says Eisenach. “Nokia continues to investigate the topic and implementation methods but the benefits appear small for most real-world applications.”
So is there much scope for further overall improvement?
“There is still a lot more juice left," says Mahajan.
“It [coherent transmission improvement] is getting harder and harder,” adds Roberts. “It is taking more mathematics and more and more CMOS gates, but Moore’s law is providing lots of CMOS gates.”
This is an updated and extended version of an article that first appeared in Optical Connections magazine earlier this year.
Infinera unveils its next-gen packet-optical platforms
Source: Infinera
Infinera has unveiled its latest metro products that support up to 200-gigabit wavelengths using CFP2-DCO pluggable modules.
The XTM II platform family is designed to support growing metro traffic, low-latency services and the trend to move sophisticated equipment towards the network edge. Placing computing, storage and even switching near the network edge contrasts with the classical approach of backhauling traffic, sometimes deep within the network.
“If you backhaul everything, you really do not know if it belongs in that part of the network,” says Geoff Bennett, director, solutions and technology at Infinera. Backhauling inherently magnifies traffic whereas operators want greater efficiencies in dealing with bandwidth growth, he says: “This is where the more cloud-like architectures towards the network edge come in.”
But locating equipment at the network edge means it must fit within existing premises or in installed prefabricated huts where space and the power supplied are constrained.
“If you are asking service providers to put more complex equipment there, then you need low power utilisation,” says Bennett. “This has been a key piece of feedback from customers we have been asking as to how they want our existing products to evolve in the metro-access.”
Having a distributed switch fabric is a long-term advantage for Infinera
Infinera says its latest XTM II products are eight times denser in terms of tranmission capacity while setting a new power-consumption low of 20W-27W per 100 gigabits depending on the operating temperature (25oC to 55oC). Infinera claims its nearest metro equipment competitor achieves 47W per 100 gigabits.
Sterling Perrin, principal analyst, optical networking and transport at Heavy Reading, says Infinera has achieved the power-efficient design by using a distributed switch architecture rather that a central switch fabric and adopting the CFP2-DCO pluggable module with its low-power coherent DSP.
“If you have a centralised fabric and you put it into an edge application then for some cases it will be a perfect fit but for many applications, it will be overkill in terms of capacity and hence power,” says Perrin. “Infinera is able to do it in a modular fashion in terms of just how much capacity and power is put in an application.”
Having a distributed switch fabric is a long-term advantage for Infinera for these applications, says Perrin, whereas competitor vendors will also benefit from the CFP2-DCO for their next designs.
And even if a competitor uses a distributed design, they will not leapfrog Infinera, says Perrin, although he expects competitors’ designs to come down considerably in power with the adoption of the CFP2-DCO.
Infinera has chosen not to use its photonic integrated circuit (PIC) technology for its latest metro platform given the large installed base of XTM chassis that already use pluggable modules. “It would make sense that customers would give feedback that they want a product that has industry-leading performance but which is also backwards compatible,” says Bennett.
Infinera has said it will evaluate whether its PIC technology will be applied to each new generation of the product line. “So when you get to the XTM III they will have another round looking at it,” says Perrin. “If I were placing bets on the XTM III, I would say they are going to continue down this route [of using pluggables].”
Perrin expects line-side pluggable technology to continue to progress with companies such as Acacia Communications and the collaboration between Ciena with its WaveLogic DSP technology and several optical module makers.
“At what point is the PIC going to be better than what is available with the pluggables?” says Perrin. “For this application, I don’t see it.”
XTM II family
Infinera has already been shipping upgraded XTM chassis for the last 18 months in advance of the launch of its latest metro cards. The upgraded chassis - the one rack unit (1RU) TM-102/II, the 3RU TM-301/II and the 11RU TM-3000/II - all feature enhanced power management and cooling.
What Infinera is unveiling now are three cards that enhance the capacity and features of the enhanced chassis. The new cards will work with the older generation XTM chassis (without the ‘II’ suffix) as long as a vacant card slot is available and the chassis’ total power supply is not exceeded. This is important given over 30,000 XTM chassis have been deployed.
The Infinera cards announced are the 400-flexponder, a 200-gigabit muxponder, and the EMXP440 packet-optical transport switch. The distributed switch architecture is implemented using the EMXP440 card.
Operators will also be offered Infinera’s Instant Bandwidth feature as part of the XTM II whereby they can pay for the line side capacity they use: either 100-gigabit or 200-gigabit wavelengths using the CFP2-DCO. The Instant Bandwidth offered is not the superchannel format available for Infinera’s other platforms that use its PIC but it does offer operators the option of deploying a higher-speed wavelength when needed and paying later.
400G flexponder
The flexponder can operate as a transponder and as a muxponder. For a transponder, the client signal and line-side data rate operate at the same data rate. In contrast, a muxponder aggregates lower data-rate client signals for transport on a single wavelength.
Infinera’s 400-gigabit flexponder card uses four 100 Gigabit Ethernet QSFP28 client interfaces and two 200-gigabit CFP2-DCO pluggable line-side modules. Each CFP2-DCO can transport data at 100 gigabits using polarisation-multiplexing, quadrature phase-shift keying (PM-QPSK) modulation or at 200 gigabits using 16-ary quadrature amplitude modulation (PM-16QAM).
The 400-gigabit card can thus operate as a transponder when the CFP2-DCO transports at 100 gigabits and as a muxponder when it carries two 100-gigabit signals over a 200-gigabit lambda. Given the card has two CFP2 line-side modules, it can even operate as a transponder and muxponder simultaneously.
The flexponder card also supports OTN block encryption using the AES-256 symmetric key protocol.
The flexponder is an upgrade on Infinera’s existing 100-gigabit muxponder card. The eightfold increase in capacity is achieved by using two 200-gigabit ports instead of a single 100-gigabit module and halving the width of the line card.
Using the flexponder card, the TM-102/II chassis has a transport capacity of 400 gigabits, up to 1.6 terabits with the TM-301/II and a total of 4 terabits using the TM-3000/II platform.
We can dial back the FEC if you need low latency and don't need the reach
200G muxponder
The double-width 200G card includes all the electronics needed for multi-service multiplexing. The line-side optics is a single CFP2-DCO module whereas the client side can accommodate two QSFP28s and 12 SFP+ 10-gigabit modules. The card can multiplex a mix of services including 10GbE, 40GbE, and 100GbE; 8-, 16- and 32-gigabit Fibre Channel; OTN and legacy SONET/SDH traffic.
Other features include support for OTN block encryption using the AES-256 symmetric key protocol.
The card’s forward error correction performance can also be traded to reduce the traffic latency. “We can dial back the FEC if you need low latency and don't need the reach,” says Bennett.
OTN add-drop multiplexing can also be implemented by pairing two of the multiplexer cards.
EMXP440 switch and flexible open line system
The EMXP440 packet-optical transport switch card supports layer-two functionality such as Carrier Ethernet 2.0 and MPLS-TP. “Mobile backhaul and residential broadband, these are the cards the operators tend to use,” says Bennett.
The two-slot EMXP440 card has two CFP2-DCOs and 12 SFP+ client-side interfaces. The reason why the line side and client side interface capacity differ (400 gigabits versus 120 gigabits) is that the card can be used to build simple packet rings (see diagram, top).
The line-side interfaces can be used for ‘East’ and ‘West' traffic while the SFP+ modules can be used to add and drop signals. The EMXP440 card also has an MPO port such that up to 12 SFP+ further ports can be added using Infinera’s PTIO-10G card, part of its PT Fabric products.
A flexible grid open line system is also available for the XTM II. The XTM II’s 100-gigabit and 200-gigabit wavelengths fit within a 50GHz-wide fixed grid channel but Infinera is already anticipating future higher baud rates that will require channels wider than 50GHz. A flexible grid also improves the use of the fibre’s overall capacity. In turn, RAMAN amplification will also be needed to extend the reach using future higher order modulation schemes such as 32- and 64-QAM.
Infinera says the 400-gigabit flexponder card will be available in the next quarter while the 200-gigabit muxponder and the EMXP440 cards will ship in the final quarter of 2017.
TIP seeks to shake up the telecom marketplace
Niall Robinson
Now, ten telcos, systems vendors, component and other players have joined Facebook as part of the Telecom Infra Project, or TIP, to bring the benefits of open-source design and white-box platforms to telecoms. TIP has over 300 members and has seven ongoing projects across three network segments of focus: access, backhaul, and core and management.
Facebook's involvement in a telecoms project is to benefit its business. The social media giant has 1.79 billion active monthly users and wants to make Internet access more broadly available. Facebook also has demanding networking requirements, both the linking of its data centres and supporting growing video traffic. It also wants better networks to support emerging services using technologies such as virtual reality headsets.
It is time to disrupt this closed market; it is time to reinvent everything we have today
The telecom operators want to collaborate with Facebook having seen how its Open Compute Project has created flexible, scalable equipment for the data centre. The operators also want to shake up the telecom industry. At the inaugural TIP summit held in November, the TIP chairman and CTO of SK Telecom, Alex Jinsung Choi, discussed how the scale and complexity of telecom networks make it hard for innovators and start-ups to enter the market. “It is time to disrupt this closed market; it is time to reinvent everything we have today,” said Choi during his TIP Summit talk.
Voyager
TIP unveiled a white-box packet optical platform dubbed Voyager at the summit. The one rack-unit (1RU) box is a project for backhaul. Voyager has been designed by Facebook and the platform’s specification has been made available to TIP.
Voyager is based on another platform Facebook has developed: the Wedge top-of-rack switch for the data centre. Wedge switches are now being made by several contract manufacturers. Each can be customised based on the operating system used and the applications loaded onboard. The goal is to adopt a similar approach with Voyager.
“Eventually, there will be something that is definitely market competitive in terms of hardware cost,” says Niall Robinson, vice president, global business development at ADVA Optical Networking, one of the companies involved in the Voyager initiative. “And you have got an open-source community developing a feature set from a software perspective.”
Other companies backing Voyager include Acacia Communications, Broadcom and Lumentum which are involved in the platform’s hardware design. Snaproute is delivering the software inside the box while first units are being made by the contract manufacturer, Celestica.
ADVA Optical Networking’s will provide a sales channel for Voyager and is interfacing it to its network management system. The system vendor will also provide services and software support. Coriant is another systems vendor backing the project. It is providing networking support including routeing and switching as well as dense WDM transmission capabilities.
This [initiative] has shown me that the whole supply and design chains for transport can be opened up; I find that fascinating.
Robinson describes TIP as one of the most ambitious and creative projects he has been involved in. “It is less around the design of the box," he says. "It is the shaking up of the ecosystem, that is what TIP is about.”
A 25-year involvement in transport has given Robinson an ingrained view that it is different to other aspects of telecom. For example, a vendor’s transport system must be at each end of the link due to the custom nature of platforms that are designed to squeeze maximum performance over a link. “In some cases, transport is different but what TIP maybe realises is that transport does not always have to be different,” says Robinson. “This [initiative] has shown me that the whole supply and design chains for transport can be opened up; I find that fascinating.”
Specification
At the core of the 1RU Voyager is the Broadcom StrataXGS Tomahawk. The 3.2-terabit switch chip is also the basis of the Wedge top-of-rack switch. The Tomahawk features 128 x 25 gigabit-per-second (Gbps) serdes to enable 32 x 100 gigabit ports, and supports layer-2 switching and layer-3 routeing.
Voyager uses 12, 100 Gigabit Ethernet client-side pluggable interfaces and four 200-gigabit networking interfaces based on Acacia’s AC-400 optical module. The AC-400 uses coherent optics and supports polarisation multiplexing, 16 quadrature amplitude modulation (PM-16QAM). “If it was a pure transport box the input rate would equal the output rate but because it is a packet box, you can take advantage of layer 2 over-subscription,” says Robinson.
At layer-3 the total routeing capacity is 2 terabits, the sum of the client and network interfaces. “At layer-3, the Tomahawk chip does not know what is a client port and what is a networking port; they are just Ethernet ports on that device,” says Robinson.
ADVA Optical Networking chose to back Voyager because it does not have a packet optical platform in its product portfolio. Until now, it has partnered with Juniper Networks and Arista Networks when such functionality has been needed. “We are chasing certain customers that are interested in Voyager,” says Robinson. “We are enabling ourselves to play in the packet optical space with a self-contained box.”
Status and roadmap
The Voyager is currently in beta-prototype status and has already been tested in trials. Equinix has tested the box working with Lumentum’s open line system over 140km of fiber, while operator MTN has also tested Voyager.
The platform is expected to be generally available in March or April 2017, by when ADVA Optical Networking will have completed the integration of Voyager with its network management system.
Robinson says there are two ways Voyager could develop.
Source: Gazettabyte
One direction is to increase the interface and switching capacities of the 1RU box. Next-generation coherent digital signal processors that support higher baud rates will enable 400Gbps and even 600Gbps wavelengths using PM-64QAM. This could enable the line-side capacity to increase from the current 800Gbps to 2 or 3 terabits. And soon, 400Gbps client-side pluggable modules will become available. Equally, Broadcom is already sampling its next-generation Tomahawk II chip that has 6.4 terabits of switching capacity.
Another direction the platform could evolve is to add an backplane to connect multiple Voyagers. This is something already done with the Wedge '6-pack' that combines six Wedge switch cards. A Voyager 6-pack would result in a packet-optical platform with multiple terabits of switching and routeing capacity.
“This is an industry-driven initiative as opposed to a company-driven one,” says Robinson. “Voyager will go whichever way the industry thinks the lowest cost is.”
Corrected on Dec 22nd. The AC-400 is a 5"x7" module and not as originally stated.
Juniper Networks to acquire Aurrion for $165 million
The announcement of the acquisition was low key. A CTO blog post and a statement that Juniper Networks had entered into an agreement to acquire Aurrion, the fabless silicon photonics start-up. No fee was mentioned.
However, in the company's US Securities and Exchange Commission filing, Juniper values the deal at approximately $165 million. "The Company believes the acquisition will help to fuel its long-term competitive advantage by enabling cost-effective, high-density, high-speed optical networks," it said. The deal is expected to be closed this quarter.
But the deal is significant for a number of reasons.
First, Aurrion, like Intel, is a proponent of heterogeneous integration, combining indium phosphide and other technologies on a silicon wafer platform through bonding. The approach has still to be proven in commercial volumes but it promises the use of III-V materials on 12-inch silicon wafers manufactured in a chip fabrication plant.
Aurrion has made tunable lasers for telecom that cover both the C- and L-bands, as well as uncooled laser arrays for datacom applications. The start-up has also been developing high-speed transceivers for the data centre.
The company has also been working on the manufacturing aspects of silicon photonics, a considerable undertaking. These include automated wafer-scale testing, connecting fibre to a silicon photonics chip, and packaging.
Juniper is thus getting an advanced silicon photonics technology suited for volume manufacturing that it will use to advance its data centre networking offerings.
Juniper may choose to make its own optical transceivers but, more likely, it will use silicon photonics as part of its switch designs to tackle issues of data centre scaling and the continual challenge of growing power consumption. It could also use the technology for its IP core routers and longer term, to tackle I/O issues alongside custom ASICs.
Systems vendors drive silicon photonics
The Aurrion acquisition also highlights how it is systems vendors that are acquiring silicon photonics start-ups rather than the traditional optical component and module makers.
This is partly a recognition that silicon photonics' main promise is as a systems technology. Acacia, the coherent transmission specialist, is one company that has shown how silicon photonics can benefit optical module design but the technology's longer-term promise is for systems design rather than optical modules.
A consequence of such acquisitions by systems vendors is that technology being developed by silicon-photonics start-ups is being swallowed within systems houses for their own use and not for the merchant market. Systems vendors have deep pockets to develop the technology but it will be for their own use. For the wider community, silicon photonics technology being developed by the likes of Aurrion is no longer available.
This is what AIM Photonics, the US public-private partnership that is developing technology for integrated photonics, is looking to address: to advance the manufacturing of silicon photonics, making the resulting technology available to small to medium sized businesses and entrepreneurial ventures. However, AIM Photonics is one year into a five-year venture.
Implications
Should major systems vendors owning silicon photonics technology in-house concern the traditional optical component vendors?
Not for now.
Optical transceiver sales continue to grow and the bulk of designs are not integrated. And while silicon photonics is starting to be used for integrated designs, it is competing against the established technologies of indium phosphide and gallium arsenide.
But as photonics moves closer to the silicon and away from a system's faceplate, silicon photonics becomes more strategically important and this is where systems vendors can start developing custom designs.
Must the systems houses own the technology to do that?
Not necessarily, but they will need silicon photonics design expertise, and in the case of Juniper, it can hit the ground running with Aurrion.
Longer term, it will be the much larger chip industry that will drive silicon photonics rather than the optical industry. There are chip foundries now that are making silicon photonic ICs as there are top-ten chip companies such as Intel and STMicroelectronics. But ultimately it will be a very different supply chain that will take shape.
It is early days but Juniper's acquisition is the latest indicator that it is the systems vendors that are moving first at the very beginnings of this new ecosystem.
Nokia’s PSE-2s delivers 400 gigabit on a wavelength
Four hundred gigabit transmission over a single carrier is enabled using Nokia’s second-generation programmable Photonic Service Engine coherent processor, the PSE2, part of several upgrades to Nokia's flagship PSS 1830 family of packet-optical transport platforms.
Kyle Hollasch“One thing that is clear is that performance will have a key role to play in optics for a long time to come, including distance, capacity per fiber, and density,” says Sterling Perrin, senior analyst at Heavy Reading.
This limits the appeal of the so-called “white box” trend for many applications in optics, he says: “We will continue to see proprietary advances that boost performance in specific ways and which gain market traction with operators as a result”.
The 1830 Photonic Service Switch
The 1830 PSS family comprises dense wavelength-division multiplexing (DWDM) platforms and packet-OTN (Optical Transport Network) switches.
The DWDM platform includes line amplifiers, reconfigurable optical add-drop multiplexers (ROADMs), transponder and muxponder cards. The 1830 platforms span the PSS-4, -8, -16 and the largest and original -32, while the 1830 PSS packet-OTN switches include the PSS-36 and the PSS-64 platforms. The switches include their own coherent uplinks but can be linked to the 1830 DWDM platforms for their line amps and ROADMs.
The 1830 PSS upgrades include a 500-gigabit muxponder card for the DWDM platforms that feature the PSE2, new ROADM and line amplifiers that will support the L-band alongside the C-band to double fibre capacity, and the PSS-24x that complements the two existing OTN switch platforms.
100-gigabit as a service
In DWDM transmissions, 100-gigabit wavelengths are commonly used to transport multiplexed 10-gigabit signals. Nokia says it is now seeing increasing demand to transport 100-gigabit client signals.
“One hundred gigabit is becoming the new currency,” says Kyle Hollasch, director, optical marketing at Nokia. “No longer is the thinking of 100 gigabit just as a DWDM line rate but 100 gigabit as a service, being handed from a customer for transport over the network.”
Current PSS 1830 platform line cards support 50-gigabit, 100-gigabit and 200-gigabit coherent transmission using polarisation-multiplexed, binary phase-shift keying (PM-BPSK), quadrature phase-shift keying (PM-QPSK) and 16 quadrature amplitude modulation (PM-16QAM), respectively. Nokia now offers a 500-gigabit muxponder card that aggregates and transports 100-gigabit client signals. The 500-gigabit muxponder card has been available since the first quarter and already several hundred cards have been shipped.
“The challenge is not just to crank up capacity but to do so profitably,” says Hollasch. “Keeping the cost-per-bit down, the power consumption down while pushing towards the Shannon limit [of fibre] to carry more capacity.”
Source: Nokia
Modulation formats
The PSE2 family of coherent processors comprises two designs: the high-end super-coherent PSE-2s and the compact low-power PSE-2c.
Nokia joins the likes of Ciena and Infinera in developing several coherent ASICs, highlighting how optical transport requirements are best met using custom silicon. Infinera also announced its latest generation photonic integrated circuit that supports up to 2.4 terabits.
The high-end PSE-2s is a significant enhancement on the PSE coherent chipset first announced in 2012. Implemented using 28nm CMOS, the PSE-2s has a power consumption similar to the original PSE yet halves the power consumption-per-bit given its higher throughput.
The PSE-2s adds four modulation formats to the PSE’s existing three and supports two symbol rates: 32.5 gigabaud and 44.5 gigabaud. The modulation schemes and distances they enable are shown in the chart.
The 1.4 billion transistor PSE-2s has sufficient processing performance to support two coherent channels. Each channel can implement a different modulation format if desired, or the two can be tightly coupled to form a super-channel. The only exception is the 400-gigabit single wavelength format. Here the PSE-2s supports only one channel implemented using a 45 gigabaud symbol rate and PM-64QAM. The 400-gigabit wavelength has a relatively short 100-150km reach, but this suits data centre interconnect applications where links are short and maximising capacity is key.
Nokia recently conducted a lab experiment resulting in the sending of 31.2 terabits of data over 90km of standard single-mode fibre using 78, 400-gigabit channels spaced 50GHz apart across the C-band. "We were only limited by the available hardware from reaching 35 terabits," says Hollasch.
Using the 45-gigabaud rate and PM-16QAM enables two 250-gigabit channels. This is how the 500-gigabit muxponder card is achieved. The 250-gigabit wavelength has a reach of 900km, and this can be extended to 1,000km but at 200 gigabit by dropping to the 32-gigabaud symbol rate, as implemented with the current PSE chipset.
Nokia also offers 200 gigabit implemented using 45 gigabaud and 8-QAM. “The extra baud rate gets us [from 150 gigabit] to 200 gigabit; this is very valuable,” says Hollasch. The resulting reach is 2,000km and he expects this format to gain the most market traction.
The PSE-2s, like the PSE, also implements PM-QPSK and PM-BPSK but with reaches of 3,000-5,000km and 10,000km, respectively.
The PSE-2s introduces a fourth modulation format dubbed set-partition QPSK (SP-QPSK).
Standard QPSK uses amplitude and phase modulation resulting in a 4-point constellation. With SP-QPSK, only three out of the possible four constellation points are used for any given symbol. The downside of the approach is that a third fewer constellation points are used and hence less data is transported but the lost third can be restored using the higher 45-gigabaud symbol rate.
The benefit of SP-QPSK is its extended reach. “By properly mapping the sequence of symbols in time, you create a greater Euclidean distance between the symbol points,” says Hollasch. “What that gives you is gain.” This 2.5dB extra gain compared to PM-QPSK equates to a reach beyond 5,000km. “That is the territory most implementation are using BPSK and also addresses a lot of sub-sea applications,” says Hollasch. “Using SP-QPSK [at 100 gigabit] also means fewer carriers and hence, it is more spectrally efficient than [50-gigabit] BPSK.”
The PSE-2c
The second coherent DSP-ASIC in the new family is the PSE-2c compact, also implemented in 28nm CMOS, designed for smaller, low-power metro platforms and metro-regional reaches.
The PSE-2c supports a 100-gigabit line rate using PM-QPSK and will be used alongside the CFP2-ACO line-side pluggable module. The PSE-2c consumes a third of the power of the current PSE operating at 100 gigabit.
“We are putting the PSE2 [processors] in multiple form factors and multiple products,” says Hollasch.
The recent Infinera and Nokia announcements highlight the electronic processing versus photonic integration innovation dynamics, says Heavy Reading's Perrin. He notes how innovations in electronics are driving transmission across greater distances and greater capacities per fibre and finding applications in both long haul and metro networks as a result.
“Parallel photonic integration is a density play, but even Infinera’s ICE announcement is a combination of photonic integration and electronic processing advancements,” says Perrin. “In our view, electronic processing has taken a front seat in importance for addressing fibre capacity and transmission distance, which is why the need for parallel photonic integration in transport has not really spread beyond Infinera so far.”
The PSS-24x showing the 24, 400 gigabit line cards and 3 switch fabric cards, 2 that are used and one for redundancy. Source: Nokia
PSS-24x OTN switch
Nokia has also unveiled its latest 28nm CMOS Transport Switch Engine, a 2.4-terabit non-blocking OTN switch chip that is central to its latest PSS-24x switch platform. Two such chips are used on a fabric card to achieve 4.8 terabits, and three such cards are used in the PSS-24x, two active cards and a third for redundancy. The result is 9.6 terabits of switching capacity instead of the current platforms' 4 terabits, while power consumption is halved.
Nokia says it already has a roadmap to 48-terabits of switching capacity. “The current generation [24x] shipping in just a few months is 400-gigabit per slot,” says Hollasch. The 24 slots that fit within the half chassis results in 9.6 terabits of switching capacity. However, Nokia's platform roadmap will achieve 1 terabit-per-slot by 2018-19. The backplane is already designed to support such higher speeds, says Hollasch. This would enable 24 terabits of switching capacity per shelf and with two shelves in a bay, a total switching capacity of 48 terabits.
The transport switch engine chip switches OTN only. It is not designed as a packet and OTN switch. “A cell-based agnostic switching architecture comes with a power and density penalty,” explains Hollasch, adding that customers prefer the lowest possible power consumption and highest possible density.
The result is a centralised OTN switch fabric with line-card packet switching. Nokia will introduce packet switching line cards next year that will support 300 gigabit per card. Two such cards will be ‘pair-able’ to boost capacity to 600 gigabit but Hollasch stresses that the PSS-24x will not switch packets through its central fabric.
Doubling capacity with the L-band
By extending the 1830 PSS platform to include the L-band, up to 70 terabits of data can be supported on a fibre, says Hollasch.
Nokia has developed a line card that supports both C-band and L-band amplification that will be available around the fourth quarter of this year. The ROADM and 500-gigabit muxponder card for the L-band will be launched in 2017.
Once the amplification is available, operators can start future-proofing their networks. Then when the L-band ROADMs and muxponder cards become available, operators can pay as they grow; extending wavelengths into the L-band, once all 96 channels of the C-band are used, says Hollasch.
The white box concept gets embraced at the optical layer
Brandon Collings
White boxes have arisen to satisfy the data centre operators’ need for simple building-block functions in large number that they can direct themselves.
“They [data centre operators] started using very simple white boxes - rather simple functionality, much simpler than the large router companies were providing - which they controlled themselves using software-defined networking orchestrators,” says Brandon Collings, CTO of Lumentum.
Such platforms have since evolved to deliver high-performance switching, controlled by third-party SDN orchestrators, and optimised for the simple needs of the data centre, he says. Now this trend is moving to the optical layer where the same flexibility of function is desired. Operators would like to better pair the functionality that they are going to buy with the exact functionality they need for their network, says Collings.
“There is no plan to build networks with different architectures to what is built today,” he says. “It is really about how do we disaggregate conventional platforms to something more flexible to deploy, to control, and which you can integrate with control planes that also manage higher layers of the network, like OTN and the packet layer.”
White box products
Lumentum has a background in integrating optical functions such as reconfigurable optical add/drop multiplexers (ROADMs) and amplifiers onto line cards, known as its TrueFlex products. “That same general element is now the element being demanded by these white box strategies, so we are putting them in pizza boxes,” says Collings.
At OFC, Lumentum announced several white box designs for linking data centres and for metro applications. Such designs are for large-scale data centre operators that use data centre interconnect platforms. But several such operators also have more complex, metro-like optical networking requirements. Traditional telcos such as AT&T are also interested in pursuing the approach.
The first Lumentum white box products include terminal and line amplifiers, a dense WDM multiplexer/ demultiplexer and a ROADM. These hardware boxes come with open interfaces so that they can be controlled by an SDN orchestrator and are being made available to interested parties.
OpenFlow, which is used for electrical switches in the data centre, could be use with such optical white boxes. Other more likely software are the Restconf and Netconf protocols. “They are just protocols that are being defined to interface the orchestrator with a collection of white boxes,” says Collings.
Lumentum’s mux-demux is defined as a white box even though it is passive and has no power or monitoring requirements. That is because the mux-demux is a distinct element that is not part of a platform.
AT&T is exploring the concept of a disaggregated ROADM. Collings says a disaggregated ROADM has two defining characteristics. One is that the hardware isn’t required to come with a full network control management system. “You can buy it and operate it without buying that same vendor’s control system,” he says. The second characteristic is that the ROADM is physically disaggregated - it comes in a pizza box rather than a custom, proprietary chassis.
There remains a large amount of value between encompassing optical hardware in a pizza box to delivering an operating network
Lumentum: a systems vendor?
The optical layer white box ecosystem continues to develop, says Collings, with many players having different approaches and different levels of ‘aggressiveness’ in pursuing the concept. There is also the issue of the orchestrators and who will provide them. Such a network control system could be written by the hyper-scale data centre operators or be developed by the classical network equipment manufacturers, says Collings.
Collings says selling pizza boxes does not make Lumentum a systems vendor. “There is a lot of value-add that has to happen between us delivering a piece of hardware with simple open northbound control interfaces and a complete deployed, qualified, engineered system.”
Control software is needed as is network engineering; value that traditional system vendors have been adding. “That is not our expertise; we are not trying to step into that space,” says Collings. There remains a large amount of value between encompassing optical hardware in a pizza box to delivering an operating network, he says.
This value and how it is going to be provided is also at the core of an ongoing industry debate. “Is it the network provider or the people that are very good at it: the network equipment makers, and how that plays out.”
Lumentum’s white box ROADM was part of an Open Networking Lab proof-of-concept demonstration at OFC.
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.”