Oclaro showcases its pluggable CFP2-DCO at ECOC
Multi-sourcing CFP2-DCO modules, coherent digital signal processor (DSP) partnerships, new laser opportunities and the latest on Lumentum’s acquisition of Oclaro. A conversation with Oclaro’s chief strategy officer, Yves LeMaitre.
Oclaro demonstrated its CFP2 Digital Coherent Optics (CFP2-DCO) pluggable module working with Acacia Communications’ own CFP2-DCO at the recent European Conference on Optical Communication (ECOC), held in Rome.
Yves LeMaitreOclaro announced earlier this year that it would use Acacia’s Meru coherent DSP for a CFP2-DCO product.
The company also announced at ECOC the availability of a portfolio of single-mode lasers that operate over an extended temperature range.
“We see two new laser opportunities for us,” says LeMaitre. “The upgrade of the access networks and, concurrently, the deployment of 5G.”
Coherent pluggables
The CFP2-DCO is a dense wavelength-division multiplexing (DWDM) module that supports 100-gigabit and 200-gigabit data rates. With the CFP2-DCO design, the coherent DSP is integrated within the module, unlike the CFP2 Analog Coherent Optics (CFP2-ACO) where the DSP chip resides on the line card.
“A concern of the market is that there has been essentially only one source of CFP2-DCO for the last few years and it was Acacia,” says LeMaitre. “Now there will be a broader supply for people who want coherent pluggables.”
Oclaro has been selling a CFP2-ACO but the company could not address those systems vendors that do not have their own DSP yet want to use coherent pluggables. “Now we can leverage our optics and combine it with Acacia’s DSP and bring another source of the CFP2-DCO,” says LeMaitre.
Acacia’s Meru is a low-power DSP that supports 200 gigabit-per-second (Gbps) wavelengths using either 8-ary quadrature amplitude modulation (8-QAM) or 16-QAM. Using 8-QAM enhances the optical reach at 200 gigabit. Oclaro’s CFP2-DCO uses its indium phosphide-based optics whereas Acacia’s module uses the company’s silicon photonics technology.
Oclaro sees the deal with Acacia as a first step, given the coming generation of 400-gigabit coherent modules including the 400ZR.
Production of Oclaro’s CFP2-DCO will commence in early 2019.
WaveLogic Ai DSP
Oclaro, along with module makers Lumentum and NeoPhotonics, signed an agreement in 2017 with Ciena to use the equipment maker’s 400-gigabit WaveLogic Ai coherent DSP. Oclaro is now shipping the 400-gigabit optical module that uses the Ciena DSP.
“The market for these types of large 400-gigabit form-factor modules in fairly limited as it is already addressed by many of the network equipment manufacturers,” says LeMaitre. “It [the module] is targeted at a few customers and a few opportunities.”
When the agreement with the three module makers was announced, there was talk of Ciena developing coherent DSPs for emerging applications such as 400-gigabit pluggables. However, Ciena has since decided to bring its own coherent modules to the marketplace and Oclaro does not yet know if it will get access to Ciena’s future coherent DSPs.
“We remain very interested in working with Ciena if they give us access to a DSP that could fit into pluggable coherent solutions but we have no agreement on that,” says LeMaitre.
There is an expectation in terms of dollar-per-bit that 400-gigabit modules are not yet meeting
Access and 5G wireless
At ECOC, Oclaro announced the availability of extended-temperature 10-gigabit and 25-gigabit lasers for access network and 5G deployments. The company also detailed its electro-absorption modulated laser (EML) supporting single-wavelength 100-gigabit transmissions for the data centre.
LeMaitre says the latest laser opportunities stem from the expansion and speed upgrades of the access infrastructure as well as upcoming 5G deployments. “This is resulting in a new lease of life for single-mode lasers because of the faster speeds and increased distances,” he says. These distances range from 10-40km and even 80km.
The environmental conditions required for these applications means the lasers must operate over industrial temperature (I-Temp) ranges, from -40 to 85oC and even higher.
Oclaro’s 25-gigabit directly-modulated laser (DML) for 5G fronthaul and mid-haul applications operates at up to 95oC. This means the laser does not need a thermo-electric cooler, simplifying the module design and reducing its power consumption. The laser has also been operated at 50 gigabit-per-second (Gbps) using 4-level pulse-amplitude modulation (PAM-4).
LeMaitre says the architectures for 5G will vary depending on the density of deployments and the primary application such as broadband or the Internet of Things.
Oclaro also announced an extended temperature range DML for 10-gigabit passive optical networks such as XGS-PON and 10GE-PON. The laser, which operates at the 1270nm wavelength, is used at the optical network unit (ONU) at the premises. Oclaro is also developing new 10-gigabit EMLs for the downstream link, from the PON optical line terminal (OLT) to the ONU. Transmission distances for such PONs can be 20km.
The company recently expanded laser production at its Japan and UK facilities, while the 10- and 25-gigabit lasers are now being mass-produced.
400 Gigabit Ethernet
Oclaro was one of five companies that took part in a 100-gigabit single-wavelength interoperability demonstration organised by the Ethernet Alliance at the show. The other four were Applied Optoelectronics, InnoLight Technology, Source Photonics, and Sumitomo Electric Industries.
The company showed its EML operating at 50 gigabaud with PAM-4 in the 100-Gigabit QSFP28 module. The 50Gbaud EML can operate uncooled such that no thermo-electric cooler is needed.
Oclaro says it will soon start sampling a 400-gigabit QSFP-DD FR4 module. The 2km four-channel FR4 developed by the 100-Gigabit Single Lambda MSA will use four 50Gbaud lasers. Volume production of the FR4 module is expected from the second quarter of 2019.
LeMaitre says 400-gigabit modules for the data centre face two key challenges.
One is meeting the power consumption of the new form factor modules such as the QSFP-DD. The optics for a four-wavelength design consumes 3-4W while the accompanying PAM-4 digital signal processor can consume 7-8W. “A transceiver burning 10-12W might be an issue for large-scale deployments,” says LeMaitre. “There is a power issue here that needs to be fixed.”
The second challenge for 400-gigabit client-side is cost. The price of 100-gigabit modules has now come down considerably. “There is an expectation in terms of dollar-per-bit that 400-gigabit modules are not yet meeting,” says LeMaitre. If the DSPs have yet to meet the power needs while the cost of the new modules is not in line with the dollar-per-bit performance of 100-gigabit modules, then 400-gigabit modules will be delayed, he says.
Acquisition
Lumentum’s acquisition of Oclaro, announced in March, continues to progress.
LeMaitre says two of the main three hurdles have now been overcome: anti-trust clearance in the U.S. and gaining shareholder approval. What remains is achieving Chinese clearance via the State Authority for Market Regulation.
“Until the merger deal is closed, we have to continue to operate as two separate companies,” says LeMaitre. But that doesn't prevent the two firms planning for the day when the deal is completed. Issues being worked through include the new organisation, the geographic locations of the companies’ groups, and how the two firms will work together to build a combined financial model.
The deal is expected to close before the year-end.
NeoPhotonics ups the baud rate for line and client optics
- Neophotonics’ 64 gigabaud optical components are now being designed into optical transmission systems. The components enable up to 600 gigabits per wavelength and 1.2 terabits using a dual-wavelength transponder.
- The company’s high-end transponder that uses Ciena’s WaveLogic Ai coherent digital signal processor (DSP) is now shipping.
- NeoPhotonic is also showcasing its 53 gigabaud components for client-side pluggable optics capable of 100-gigabit wavelengths at the current European Conference on Optical Communication (ECOC) show being held in Rome.
NeoPhotonics says its family of 64 gigabaud (Gbaud) optical components are being incorporated within next-generation optical transmission platforms.
Ferris LipscombThe 64Gbaud components include a micro intradyne coherent receiver (micro-ICR), a micro integrable tunable laser assembly (micro-ITLA) and a coherent driver modulator (CDM).
The micro-ICR and micro-ITLA are the Optical Internetworking Forum’s (OIF) specification, while the CDM is currently being specified.
“Three major customers have selected to use all three [64Gbaud components] and several others are using a subset of those,” says Ferris Lipscomb, vice president of marketing at NeoPhotonics.
NeoPhotonics also unveiled and demonstrated two smaller 64Gbaud component designs at the OFC show held in March. The devices - a coherent optical sub-assembly (COSA) and a nano-ITLA - are aimed at 400-gigabit coherent pluggable modules as well as compact line-card designs.
“These [two compact components] continue to be developed as well,” says Lipscomb.
Baud rate and modulation
The current 100-gigabit coherent transmission uses polarisation-multiplexing, quadrature phase-shift keying (PM-QPSK) modulation operating at 32 gigabaud. The 100 gigabits-per-second (Gbps) data rate is achieved using four bits per symbol and a symbol rate of 32Gbaud.
Optical designers use two approaches to increase the wavelength’s data rate beyond 100Gbps. One approach is to increase the modulation scheme beyond QPSK using 16-ary quadrature amplitude modulation (16-QAM) or 64-QAM, the other is to increase the baud rate.
“The baud rate is the on-off rate as opposed to the bit rate. That is because you are packing more bits in there than the on-off supports,” says Lipscomb. “But if you double the on-off rate, you double the number of bits.”
Doubling the baud rate from 32Gbaud to 64Gbaud achieves just while using 64-QAM trebles the data sent per symbol compared to 100-gigabit PM-QSPK. Combining the two - 64Gbaud and 64-QAM - creates the 600 gigabits per wavelength.
A higher baud rate also has a reach advantage, says Lipscomb, with its lower noise. “For longer distances, increasing the baud rate is better.”
But doubling the baud rate requires more capable DSPs to interpret things at twice the rate. “And such DSPs now exist, operating at 64Gbaud and 64-QAM,” he says.
Three major customers have selected to use all three [64Gbaud components] and several others are using a subset of those
Coherent components
NeoPhotonics’ 64Gbaud optical components are suitable for line cards, fixed-packaged transponders, 1-rack-unit modular platforms used for data centre interconnect and the CFP2 pluggable form factor.
For data centre interconnect using 600-gigabits-per-wavelength transmissions, the distance achieved is up to 100km. For longer distances, the 64Gbaud components achieve metro-regional reaches at 400Gbps, and 2,000km for long-haul at 200Gbps.
But to fit within the most demanding pluggable form factors such as the OSFP and QSFP-DD, smaller componentry is required. This is what the coherent optical sub-assembly (COSA) and nano-ITLA are designed to address. The COSA combines the coherent modular driver and the ICR in a single gold-box package that is no larger than the individual 64Gbaud micro-ICR and CDM packages.
Source: Gazettabyte
“There is a lot of interest in 400-gigabit applications for a CFP2, and in that form factor you can use the separate components,” says Lipscomb. “But for data centre interconnect, you want to increase the density as much as possible so going to the smaller OSPF or QSFP-DD requires another generation of [component] shrinking.”
NeoPhotonics says there are two main approaches. One, and what NeoPhotonics has done with the nano-ITLA and COSA, is to separate the laser from the remaining circuitry such that two components are needed overall. A benefit of a separate laser is also lower noise. “But the ultimate approach would be to put all three in one gold box,” says Lipscomb.
For data centre interconnect, you want to increase the density as much as possible so going to the smaller OSPF or QSFP-DD requires another generation of [component] shrinking
Both approaches are accommodated as part of the OIF’s Integrated Coherent Transmitter-Receiver Optical Sub-Assembly (IC-TROSA) project.
Another challenge to achieving coherent designs such as the emerging 400ZR standard using the OSFP or QSFP-DD is accommodating the DSP with the optics while meeting the modules’ demanding power constraints. This requires a 7nm CMOS DSP and first samples are expected by year-end with limited production occurring towards the end of 2019. Volume production of coherent OSFP and QSFP-DD modules are expected in 2020 or even 2021, says Lipscomb.
100G client-side wavelengths
NeoPhotonics also used the OFC show last March to detail its 53Gbaud components for client-side pluggables that are 100-gigabit single-wavelength and four-wavelength 400-gigabit designs. Samples of these have now been delivered to customers and are part of demonstrations at ECOC this week.
The components include an electro-absorption modulated laser (EML) and driver for the transmitter, and photodetectors and trans-impedance amplifiers for the receiver path. The 53Gbaud EML can operate uncooled, is non-hermetic and is aimed for use with OSFP and QSFP-DD modules.
To achieve a 100-gigabit wavelength, 4-level pulse-amplitude modulation (PAM-4) is used and that requires an advanced DSP. Such PAM-4 DSPs will only be available early next year, says NeoPhotonics.
The first 400-gigabit modules using 100-gigabit wavelengths will gain momentum by the end of 2019 with volume production in 2020, says Lipscomb.
The various 8-wavelength implementations such as the IEEE-defined 2km 400GBASE-FR8 and 10km 400GBASE-LR8 are used when data centre operators must have 400-gigabit client interfaces.
The adoption of 100-gigabit single-wavelength implementations of 400 gigabits, in contrast, will be adopted when it becomes cheaper on a cost-per-bit basis, says Lipscomb: “It [100-gigabit single-wavelength-based modules] will be a general replacement rather than a breaking of bottlenecks.”
NeoPhotonics is also making available its DFB laser technology for silicon-photonics-based modules such as the 2km 400G-FR4, as well as the 100-gigabit single-wavelength DR1 and the parallel-fibre 400-gigabit DR4 standards.
WaveLogic AI transponder
NeoPhotonics has revealed it is shipping its first module using Ciena’s WaveLogic Ai coherent DSP. “We are shipping in modest volumes right now,” says Lipscomb.
The company is one of three module makers, the others being Lumentum and Oclaro, that signed an agreement with Ciena to use of its flagship WaveLogic Ai DSP for their coherent module designs.
Lipscomb describes the market for the module as a niche given its high-end optical performance, what he describes as a fully capable, multi-haul transponder. “It has lots of features and a lot of expense too,” he says. “It is applied to specific cases where long distance is needed; it can go 12,000km if you need it to.”
The agreement with Ciena also includes the option to use future Ciena DSPs. “Nothing is announced yet and so we will have to see how that all plays out.”
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.
Oclaro makes available its EMLs and backs 400G-FR4
Lumentum’s plan to acquire Oclaro for $1.8 billion may have dominated the news at last month’s OFC show held in San Diego, but it was business as usual for Oclaro with its product and strategy announcements.
Adam Carter, chief commercial officer (pictured), positions Oclaro’s announcements in terms of general industry trends.
“On the line side, everywhere there are 100-gigabit and 200-gigabit wavelengths, you will see that transition to 400 gigabit and 600 gigabit,” he says. “And on the client side, you have 100 gigabit going to 400 gigabit.”
400G-FR
Oclaro announced it will offer the QSFP56-DD module implementing 400-FR4, the four-wavelength 400-gigabit 2km client-side interface. The 400G-FR4 is a design developed by the 100G Lambda MSA.
“This [QSFP-DD FR4] will enable our customers, particularly network equipment manufacturers, to drive 400 gigabit up to 36 ports in a one-rack-unit [platform],” says Carter.
Oclaro has had the required optical components - its 53-gigabaud lasers and high-end photo-detectors - for a while. What Oclaro has lacked is the accompanying 4-level pulse amplitude modulation (PAM-4) gearbox chip to take the 8x50 gigabits-per-second electrical signals and encode them into four 50-gigabaud ones.
The chips have now arrived for testing and if the silicon meets the specs, Oclaro will deliver the first modules to customers later this year.
Oclaro chose the QSFP-DD first as it expects the form factor to sell in higher volumes but it will offer the 400G-FR4 in the OSFP module.
Certain customers prefer the OSFP, in part because of its greater power-handling capabilities. “Some people believe that the OSFP’s power envelope gives you a little bit more freedom,” he says. “There is still a debate in the industry whether the QSFP-DD will be able to do long-reach [80km data centre interconnect] types of products.”
Oclaro says its transmit and receive optical sub-assemblies (TOSAs and ROSAs) are designed to fit within the more demanding QSFP-DD such they will also suit the OSFP.
If people want to buy the [EML] chips and do next-generation designs, they can come to Oclaro
EMLs for sale
Oclaro has decided to sell its electro-absorption modulated lasers (EMLs), capable of 25, 50 and 100-gigabit speeds.
“If people want to buy the chips and do next-generation designs, they can come to Oclaro for some top-end single-mode chipsets that we have developed for our own use,” says Carter.
Oclaro's EMLs are used for both coarse wavelength-division multiplexing (CWDM) and the tighter LAN-WDM wavelength grid based client-side interfaces and are available in uncooled and cooled packages.
Until now the company only sold its 25-gigabit directly modulated lasers (DMLs). “We have been selling [EMLs] strategically to one very large customer who consigns them to a manufacturer,” says Carter.
The EMLs are being made generally available due to demand. “There are not many manufacturers of this chip in the world,” says Carter, adding that the decision also reflects an evolving climate for business models.
5G and cable
Oclaro claims it is selling the industry’s first 10-gigabit tunable SFP+ operating over industrial temperature (I-temp) ranges: -40 to 85oC. There are two tunable variants spanning 40km and 80km, both supporting up to 96 dense WDM (DWDM) channels on a fibre. The module was first announced at OFC 2017.
Oclaro says cable networks and 5G wireless will require the I-temp tunable SFP+.
The cable industry’s adoption of a distributed access architecture (DAA) 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 the residential units. This helps cable operators cope with continual traffic growth and their facilities becoming increasingly congested with equipment. Comcast, for example, says it is seeing an annual growth in downstream traffic (to the home) of 40-50 percent.
The use of tunable SFP+ modules boost the capacity that can be sent over a fibre, says Carter. But the tunable SFP+ modules are now located at the remote PHY, an uncontrolled temperature environment.
For 5G, the 10Gbps tunables will carry antenna traffic to centralised base stations. Carter points out that the 40km and 80km reach of the tunable SFP+ will not be needed in all geographies but in China, for example, the goal is to limit the number of central offices such that the distances are greater.
Oclaro also offers an I-temp fixed-wavelength 25-gigabit SFP28 LR module. “It is lower cost than the tunable SFP+ so if you need 10km [for mobile fronthaul], you would tend to go for this transceiver,” says Carter.
Also unveiled is an optical chip combining a 1310nm distributed feedback laser (DFB) laser and a Mach-Zehnder modulator. “The 1310nm device will be used in certain applications inside the data centre,” says Carter. “There are customers that are looking at using PAM-4 interfaces for short-reach connections between leaf and spine switches.” The device will support 50-gigabit and 100-gigabit PAM-4 wavelengths.
Line-side optics
Oclaro announced it is extending its integrated coherent transmitter and integrated coherent receiver to operate in the L-band. The coherent optical devices support a symbol rate of up to 64 gigabaud to enable 400-gigabit and 600-gigabit wavelengths.
Telcos want to use the L-band alongside the C-band to effectively double the capacity of a fibre.
Also announced by Oclaro at OFC was a high-bandwidth co-packaged modulator driver, an indium phosphide-based Mach-Zehnder modulator.
Oclaro was part of the main news story at last year’s OFC when Ciena announced it would share its 400-gigabit WaveLogic Ai coherent digital signal processor (DSP) with three module makers: Oclaro, Lumentum and NeoPhotonics. Yet there was no Oclaro announcement at this year’s OFC regarding the transponder.
Carter says the WaveLogic Ai transponder is sampling and that it has been demonstrated to customers and used in several field trials: “It is still early right now with regard volume deployments so there is nothing to announce yet."
Verizon, Ciena and Juniper trial 400 Gigabit Ethernet
Verizon has sent a 400 Gigabit Ethernet signal over its network, carried using a 400-gigabit optical wavelength.
The trial’s goal was to demonstrate multi-vendor interoperability and in particular the interoperability of standardised 400 Gigabit Ethernet (GbE) client signals.
Glenn Wellbrock“[400GbE] Interoperability with the client side has been the long pole in the tent - and continues to be,” says Glenn Wellbrock, director, optical transport network - architecture, design and planning at Verizon. “This was trial equipment, not generally-available equipment.”
It is only the emergence of standardised modules - in this case, an IEEE 400GbE client-side interface specification - that allows multi-vendor interoperability, he says.
By trialing a 400-gigabit lightpath, Verizon also demonstrated the working of a dense wavelength-division multiplexing (DWDM) flexible grid, and a baud rate nearly double the 32-35Gbaud in wide use for 100-gigabit and 200-gigabit wavelengths.
“It shows we can take advantage of the entire system; we don’t have to stick to 50GHz channel spacing anymore,” says Wellbrock.
[400GbE] Interoperability with the client side has been the long pole in the tent - and continues to be
Trial set-up
The trial used Juniper Networks’ PTX5000 packet transport router and Ciena’s 6500 packet-optical platform, equipment already deployed in Verizon’s network.
The Verizon demonstration was not testing optical transmission reach. Indeed the equipment was located in two buildings in Richardson, within the Dallas area. Testing the reach of 400-gigabit wavelengths will come in future trials, says Wellbrock.
The PTX5000 core router has a traffic capacity of up to 24 terabits and supports 10-gigabit, 40-gigabit and 100-gigabit client-side interfaces as well as 100-gigabit coherent interfaces for IP-over-DWDM applications. The PTX5000 uses a mother card on which sits one or more daughter cards hosting the interfaces, what Juniper calls a flexible PIC concentrator (FPC) and physical interface cards (PICs), respectively.
Juniper created a PIC with a 400GbE CFP8 pluggable module implementing the IEEE’s 10km 400GBASE-LR8 standard.
“For us, it was simply creating a demo 400-gigabit pluggable line card to go into the line card Verizon has already deployed,” says Donyel Jones-Williams, director of product marketing management at Juniper Networks.
Donyel Jones-WilliamsThe CFP8 400GbE interface connected the router to Ciena’s 6500 packet-optical platform.
Ciena also used demonstration hardware developed for 400-gigabit trials. “We expect to develop other hardware for general deployment,” says Helen Xenos, senior director, portfolio marketing at Ciena. “We are looking at smaller form-factor pluggables to carry 400 Gigabit Ethernet.”
400-gigabit deployments and trials
Ciena started shipping its WaveLogic Ai coherent modem that implements 400-gigabit wavelengths in the third quarter of 2017. Since then, the company has announced several 400-gigabit deployments and trials.
Vodafone New Zealand deployed 400 gigabits in its national transport network last September, a world first, claims Ciena. German cable operator, Unitymedia, has also deployed Ciena’s WaveLogic Ai coherent modem to deliver a flexible grid and 400-gigabit wavelengths to support growing content delivered via its data centres. And JISC, which runs the UK’s national research and education network, has deployed the 6500 platform and is using 400-gigabit wavelengths.
Helen Xenos
Last September, AT&T conducted its own 400-gigabit trial with Ciena. With AT&T’s trial, the 400-gigabit signal was generated using a test bed. “An SDN controller was used to provision the circuit and the [400-gigabit] signal traversed an OpenROADM line system,” says Xenos.
Using the WaveLogic Ai coherent modem and its support for a 56Gbaud rate means that tunable capacity can now be doubled across applications, says Xenos. The wavelength capacity used for long-haul distances can now be 200 gigabits instead of 100 gigabits, while metro-regional networks spanning 1,000km can use 300-gigabit wavelengths. Meanwhile, 400-gigabit lightpaths suit distances of several hundred kilometres.
It is the large data centre operators that are driving the majority of 400 gigabit deployments, says Ciena. The reason the 400-gigabit announcements relate to telecom operators is because the data centre players have not gone public with their deployments, says Xenos.
Juniper Networks’ PTX5000 core router with 400GbE interfaces will primarily be used by the telecom operators. “We are in trials with other providers on 400 gigabits,” says Jones-Williams. “Nothing is public as yet.”
Oclaro’s 400-gigabit plans
Adam Carter, Oclaro’s chief commercial officer, discusses the company’s 400-gigabit and higher-speed coherent optical transmission plans and the 400-gigabit client-side pluggable opportunity.
Oclaro showcased its first coherent module that uses Ciena’s WaveLogic Ai digital signal processor at the ECOC show held recently in Gothenburg.
Adam CarterOclaro is one of three optical module makers, the others being Lumentum and NeoPhotonics, that signed an agreement with Ciena earlier this year to use the system vendor’s DSP technology and know-how to bring coherent modules to market. The first product resulting from the collaboration is a 5x7-inch board-mounted module that supports 400-gigabits on a single-wavelength.
The first WaveLogic Ai-based modules are already being tested at several of Oclaro’s customers’ labs. “They [the module samples] are very preliminary,” says Adam Carter, the chief commercial officer at Oclaro. “The really important timeframe is when we get towards the new year because then we will have beta samples.”
DSP developments
The coherent module is a Ciena design and Carter admits there isn’t going to be much differentiation between the three module makers’ products.
“We have some of the key components that sit inside that module and the idea is, over time, we would design in the rest of the componentry that we make that isn’t already in there,” says Carter. “But it is still going to be the same spec between the three suppliers.”
The collaboration with the module makers helps Ciena promote its coherent DSP to a wider market and in particular China, a market where its systems are not deployed.
Over time, the scope for differentiation between the three module makers will grow. “It [the deal] gives us access to another DSP chip for potential future applications,” says Carter.
Here, Oclaro will be the design authority, procuring the DSP chip for Ciena before adding its own optics. “So, for example, for the [OIF’s] 400G ZR, we would ask Ciena to develop a chip to a certain spec and then put our optical sub-assemblies around it,” says Carter. “This is where we do believe we can differentiate.”
Oclaro also unveiled at ECOC an integrated coherent transmitter and an intradyne coherent receiver optical sub-assemblies using its indium phosphide technology that operate at up to 64 gigabaud (Gbaud).
We expect to see 64Gbaud optical systems being trialed in 2018 with production systems following at the end of next year
A 64Gbaud symbol rate enables a 400-gigabit wavelength using 16-ary quadrature amplitude modulation (16-QAM) and a 600-gigabit wavelength using 64-QAM.
Certain customers want such optical sub-assemblies for their line card designs and Oclaro will also use the building blocks for its own modules. The devices will be available this quarter. “We expect to see 64Gbaud optical systems being trialed in 2018 with production systems following at the end of next year and the beginning of 2019,” says Carter.
Oclaro also announced that its lithium niobate modulator supporting 400-gigabit single wavelengths is now in volume production. “Certain customers do have their preferences when it comes to first designs and particularly for long-reach systems,” says Carter. “Lithium niobate seems to be the one people go with.”
400-gigabit form factors
Oclaro did not make any announcements regarding 400-gigabit client-side modules at ECOC. At the OFC show held earlier this year, it detailed two CFP8-based 400-gigabit designs based on eight wavelengths with reaches of 10km and 40km.
“We are sampling the 400-gigabit 10km product right now,” says Carter. “The product is being tested at the system level and will go through various qualification runs.”
The 40km CFP8 product is further out. There are customers interested in such a module as they have requirements to link IP routers that are more than 10km apart.
Carter describes the CFP8 400-gigabit modules as first-generation products. The CFP8 is similar in size to the CFP2 pluggable module and that is too large for the large-scale data centre players. They want higher aggregate bandwidth and greater front panel densities for their switches and are looking such form factors as the double-density QSFP (QSFP-DD) and the Octal Small Form Factor pluggable (OSFP).
The OSFP is a fresh design, has a larger power envelope - some 15W compared to the 12W of the QSFP-DD - and has a roadmap that supports 800-gigabit data rates. In contrast, the QSFP-DD is backward compatible with the QSFP, an attractive feature for many vendors.
But it is not only a module’s power envelope that is an issue for 400-gigabit designs but also whether a one-rack-unit box can be sufficiently cooled when fully populated to avoid thermal runaway. Some 36 QSFP-DDs can fit on the front panel compared to 32 OSFPs.
Carter stresses both form factors can’t be dismissed for 400-gigabit: “Everyone is pursuing designs that are suitable for both.” Oclaro is not an advocate of either form factor given it provides optical sub-assemblies suitable for both.
The industry really wants four-channels. When you use more lasers, you are adding more cost.
Optical formats
Oclaro’s core technology is indium phosphide and, as such, its focusses on single-mode fibre designs.
The single mode options for 400 gigabits are split between eight-wavelength designs such as the IEEE 802.3bs 2km 400GBASE-FR8 and 10km 400GBASE-LR8 and the newly announced CWDM8 MSA, and four-wavelength specifications - the 500m IEEE 802.3bs parallel fibre 400GBASE-DR4 and the 2km 100G Lambda MSA 400G-FR4 that is under development. Oclaro is a founding member of the 100 Gigabit Lambda MSA but has not joined the CWDM8 MSA.
"The industry really wants four channels," says Carter. "When you use more lasers, you are adding more cost." It is also not trivial fitting eight lasers into a CFP8 never mind into the smaller QSFP-DD and OSFP modules.
“There might be some that have the technology to do the eight-channel part and there might be customers that will use that,” says Carter. “But most of the discussions we’ve been having are around four channels.”
Challenges
The industry’s goal is to have 400-gigabit QSFP-DD and OSFP module in production by the end of next year and into 2019. “There is still some risk but everybody is driving to meet that schedule,” says Carter.
Oclaro says first samples of 100-gigabit PAM-4 chips needed for 100-gigabit single wavelengths are now in the labs. Module makers can thus add their optical sub-assemblies to the chips and start testing system performance. Four-channel PAM-4 chips will be needed for the 400-gigabit module products.
Carter also acknowledges that any further delay in four-wavelength designs could open the door for other 400-gigabit solutions and even interim 200-gigabit designs.
“As a transceiver supplier and an optical component supplier you are always aware of that,” he says. “You have to have backup plans if that comes off.”
Real-time visibility makes optical networking smarter
Systems vendors are making optical networks smarter. Their latest equipment, combining intelligent silicon and software, can measure the status of the network and enable dynamic network management.
Ciena recently announced its Liquid Spectrum networking product while Infinera has launched its Instant Network. Both vendors exploit the capabilities of their latest generation coherent DSPs to allow greater network automation and efficiency. The vendors even talk about their products being an important step towards autonomous or cognitive networks.
"Operators need to do things more efficiently," says Helen Xenos, director, portfolio solutions marketing at Ciena. "There is a lot of unpredictability in how traffic needs to be connected over the network." Moreover, demands on the network are set to increase with 5G and the billions of devices to be connected with the advent of Internet of Things.
Existing optical networks are designed to meet worse-case conditions. Margins are built into links based on the fibre used and assumptions are made about the equipment's end-of-life performance and the traffic to be carried. Now, with Ciena's latest WaveLogic Ai coherent DSP-ASIC, not only is the performance of the network measured but the coherent DSP can be used to exploit the network's state rather than use the worse-case end-of-life conditions. "With Liquid Spectrum, you now don't need to operate the network in a static mode," says Xenos.
We are at the beginning of this new world of operating networks
Software applications
Ciena has announced the first four software applications as part of Liquid Spectrum. The first, Performance Meter, uses measured signal-to-noise ratio data from the coherent DSP-ASICs to gauge the network's state to determine how efficiently the network is operating.
Bandwidth Optimiser acts on the network planner's request for bandwidth. The app recommends the optimum capacity that can be run on the link, based on exploiting baud rate and the reach, and also where to place the wavelengths within the C-band spectrum. Moreover, if service demands change, the network engineer can decide to reduce the built-in margins. "I may decide I don't need to reserve a 3dB margin right now and drop it down to 1dB," says Xenos. Bandwidth Optimiser can then be rerun to see how the new service demand can be met.
This approach contrasts with the existing way end points are connected, where all the wavelengths used are at the same capacity, a user decides their wavelengths and no changes are made once the wavelengths are deployed. "It is much simpler, it [the app] takes away complexity from the user," says Xenos.
The Liquid Restoration app ensuring alternative capacity in response to the loss of a 300-gigabit route due to a fault. Source: Ciena
The two remaining apps launched are Liquid Restoration and Wave-Line Synchroniser. Liquid Restoration looks at all the available options if a particular path fails. "It will borrow against margin to get as much capacity as possible," says Xenos. Wave-Line Synchroniser is a tool that helps with settings so that Ciena's optics can work with another vendor's line system or optics from another vendor work with Ciena's line system.
Liquid Spectrum will be offered as a bundle as part of Ciena's latest BluePlanet Manage, Control and Plan tool that combines service and network management, resource control and planning.
Xenos says Liquid Spectrum represents the latest, significant remaining piece towards the industry's goal of developing an agile optical infrastructure. Sophisticated reconfigurable optical add-drop multiplexers (ROADMs) and flexible coherent DSPs have existed for a while but how such flexible technology has been employed has been limited because of the lack of knowledge of the real-time state of the network. Moreover, with these latest Liquid Spectrum software tools, much of the manual link engineering and complexity regarding what capacity can be supported and where in the spectrum it should be placed, says Xenos.
"We are at the beginning of this new world of operating networks," says Xenos. "Going forward, there will be an increasingly level of sophistication that will be built into the software."
Ciena demonstrated Liquid Spectrum at the OFC show held in Los Angeles last month.
Part 2: Infinera's Instant Network, click here
Ciena brings data analytics to optical networking
- Ciena's WaveLogic Ai coherent DSP-ASIC makes real-time measurements, enabling operators to analyse and adapt their networks.
- The DSP-ASIC supports 100-gigabit to 400-gigabit wavelengths in 50-gigabit increments.
- The WaveLogic Ai will be used in Ciena’s systems from 2Q 2017.
Ciena has unveiled its latest generation coherent DSP-ASIC. The device, dubbed WaveLogic Ai, follows Ciena’s WaveLogic 3 family of coherent chips which was first announced in 2012. The Ai naming scheme reflects the company's belief that its latest chipset represents a significant advancement in coherent DSP-ASIC functionality.
Helen XenosThe WaveLogic Ai is Ciena's first DSP-ASIC to support two baud rates, 35 gigabaud for fixed-grid optical networks and 56 gigabaud for flexible-grid ones. The design also uses advanced modulation schemes to optimise the data transmission over a given link.
Perhaps the most significant development, however, is the real-time network monitoring offered by the coherent DSP-ASIC. The data will allow operators to fine-tune transmissions to adapt to changing networking conditions.
“We do believe we are taking that first step towards a more automated network and even laying the foundation for the vision of a self-driving network,” says Helen Xenos, director, portfolio solutions marketing at Ciena.
All those assumptions of the past [based on static traffic] aren't holding true anymore
Network Analytics
Conservative margins are used when designing links due to a lack of accurate data regarding the optical network's status. This curtails the transmission capacity that can be sent since a relatively large link margin is used. In turn, cloud services and new applications mean networks are being exercised in increasingly dynamic ways. “The business environment has changed a little bit,” says Joe Cumello, vice president, portfolio marketing at Ciena. “All those assumptions of the past [based on static traffic] aren't holding true anymore.”
Ciena is being asked by more and more operators to provide information as to what is happening within their networks. Operators want real-time data that they can feed to analytics software to make network optimisation decisions. "Imagine a network where, instead of those rigid assumptions in place, run on manual spreadsheets, the network is making decisions on its own," says Cumello.
WaveLogic Ai performs real-time analysis, making available network measurements data every 10ms. The data can be fed through application programming interfaces to analytics software whose output is used by operators to adapt their networks.
Joe Cumello
The network parameters collected include the transmitter and receiver optical power, polarisation channel and chromatic dispersion conditions, error rates and transmission latency. In addition, the DSP-ASIC separates the linear and non-linear noise components of the signal-to-noise ratio. An operator will thus see what the network margin is and allow links to operate more closely to the limit, improving transmissions by exploiting the WaveLogic Ai's 50-gigabit transmission increments.
"Maybe there are only a few wavelengths in the network such that the capacity can be cranked up to 300 gigabits. But as more and more wavelengths are added, if you have the tools, you can tell the operator to adjust,” says Xenos. “This helps them get to the next level; something that has not been available before.”
WaveLogic Ai
The WaveLogic Ai's lower baud rate - 35 gigabaud - is a common symbol rate used by optical transmission systems today. The baud rate is suited to existing fixed-grid networks based on 50GHz-wide channels. At 35 gigabaud, the WaveLogic Ai supports data rates from 100 to 250 gigabits-per-second (Gbps).
The second, higher 56 gigabaud rate enables 400Gbps single-wavelength transmissions and supports data rates of 100 to 400Gbps in increments of 50Gbps.
Using 35 gigabaud and polarisation multiplexing, 16-ary quadrature amplitude modulation (PM-16QAM), a 200-gigabit wavelength has a reach is 1,000km.
With 35-gigabaud and 16-QAM, effectively 8 bits per symbol are sent.
In contrast, 5 bits per symbol are used with the faster 56 gigabaud symbol rate. Here, a more complex modulation scheme is used based on multi-dimensional coding. Multi-dimensional formats add additional dimensions to the four commonly used based on real and imaginary signal components and the two polarisations of light. The higher dimension formats may use more than one time slot, or sub-carriers in the frequency domain, or even use both techniques.
For the WaveLogic Ai, the 200-gigabit wavelength at 56 gigabaud achieves a reach of 3,000km, a threefold improvement compared to using a 35 gigabaud symbol rate. The additional reach occurs because fewer constellation points are required at 56 gigabaud compared to 16-QAM at 35 gigabaud, resulting in a greater Euclidean distance between the constellation points. "That means there is a higher signal-to-noise ratio and you can go a farther distance," says Xenos. "The way of getting to these different types of constellations is using a higher complexity modulation and multi-dimensional coding."
We do believe we are taking that first step towards a more automated network and even laying the foundation for the vision of a self-driving network
The increasingly sophisticated schemes used at 56 gigabaud also marks a new development whereby Ciena no longer spells out the particular modulation scheme used for a given optical channel rate. At 56 gigabaud, the symbol rate varies between 4 and 10 bits per symbol, says Ciena.
The optical channel widths at 56 gigabaud are wider than the fixed grid 50GHz. "Any time you go over 35 gigabaud, you will not fit [a wavelength] in a 50GHz band," says Xenos.
The particular channel width at 56 gigabaud depends on whether a super-channel is being sent or a mesh architecture is used whereby channels of differing widths are added and dropped at network nodes. Since wavelengths making up a super-channel go to a single destination, the channels can be packed more closely, with each channel occupying 60GHz. For the mesh architecture, guard bands are required either side of the wavelength such that a 75GHz optical channel width is used.
The WaveLogic Ai enables submarine links of 14,000km at 100Gbps, 3,000km links at 200Gbps (as detailed), 1,000km at 300Gbps and 300km at 400Gbps.
Hardware details
The WaveLogic Ai is implemented using a 28nm semiconductor process known as fully-depleted silicon-on-insulator (FD-SOI). "This has much lower power than a 16nm or 18nm FinFET CMOS process," says Xenos. (See Fully-depleted SOI vs FinFET)
Using FD-SOI more than halves the power consumption compared to Ciena’s existing WaveLogic 3 coherent devices. "We did some network modelling using either the WaveLogic 3 Extreme or the WaveLogic 3 Nano, depending on what the network requirements were," says Xenos. "Overall, it [the WaveLogic Ai] was driving down [power consumption] more than 50 percent." The WaveLogic 3 Extreme is Ciena's current flagship coherent DSP-ASIC while the Nano is tailored for 100-gigabit metro rates.
Other Ai features include support for 400 Gigabit Ethernet and Flexible Ethernet formats. Flexible Ethernet is designed to support Ethernet MAC rates independent of the Ethernet physical layer rate being used. Flexible Ethernet will enable Ciena to match the client signals as required to fill up the variable line rates.
Further information:
SOI Industry Consortium, click here
STMicroelectronics White Paper on FD-SOI, click here
Other coherent DSP-ASIC announcements in 2016
Infinera's Infinite Capacity Engine, click here
Nokia's PSE-2, click here