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.
Finisar demonstrates its first silicon photonics transceiver
- Finisar unveiled its first silicon photonics-based product, a 400-gigabit QSFP-DD DR4 module, at the recent ECOC event.
- The company also showed transceiver technology that simplifies the setting up of dense wavelength-division multiplexing (DWDM) links.
- Two 200-gigabit QSFP56 client-side modules and an extended reach 30km 400-gigabit eLR8 were also demonstrated by Finisar.
- A 64-gigabaud integrated tunable transmitter and receiver assembly (ITTRA) was used to send a 400-gigabit coherent wavelength.
Finisar is bringing to market its first silicon photonics-based optical module.
Christian UrricarietThe 400GBASE-DR4 is an IEEE 500m-reach 400-gigabit parallel fibre standard based on four fibres, each carrying a 100-gigabit 4-level pulse amplitude modulation (PAM-4) signal. Finisar’s DR4 is integrated into a QSFP-DD module.
“The DR4 is the 400-gigabit interface that most of the hyperscale cloud players are interested in first,” says Christian Urricariet, senior director of global marketing at Finisar.
The company demonstrated the module at the recent European Conference on Optical Communication (ECOC), held in Rome.
Silicon photonics-based DR4
The DR4 is an integrated design, says Finisar, comprising modulators and photo-detectors as well as modulator drivers and the trans-impedance amplifiers (TIAs).
Finisar chose silicon photonics for the DR4 after undertaking an extensive technology study. Silicon photonics emerged as ‘a clear winner’ in terms of cost and performance for photonic designs made up of similar functions in parallel, such as the four-channel DR4. Silicon photonics manufacturing is also scalable, making it ideal for high-volume designs.
The DR4 is the 400-gigabit interface that most of the hyperscale cloud players are interested in first
The DR4 can also be used in a breakout mode to interface to four 100GBASE-DR modules. Also referred to as the DR1, the 100GBASE-DR fits within an SFP-DD or a QSFP28 module.
The DR4-DR1 combination can link four servers, each using a 100-gigabit link, to a 400-gigabit port on a top-of-rack or mid-row switch. The top-of-rack 400-gigabit DR4 can also connect to a leaf switch with multiple 100-gigabit ports. “The DR4 can be used ‘top-of-rack down’ [to servers] or ‘top-of-rack up’ [to leaf switches],” says Urricariet. “This is similar to what people are doing with the [100-gigabit parallel fibre] PSM4.”
400-gigabit eLR8
Finisar also showcased an extended reach version of the IEEE 400GBASE-LR8 standard.
Dubbed the eLR8, the QSFP-DD module is a technology demonstrator not a product that extends the reach of the LR8 from 10km to 30km.
Finisar already has an LR8 product in a CFP8 pluggable module and is moving the design to the smaller QSFP-DD. The LR8 is an eight-wavelength duplex interface where each wavelength carries a 50-gigabit PAM-4 signal.
“The 400GBASE-LR8 is a low-risk approach to achieving a 400-gigabit duplex single-mode link in the short term,” says Urricariet. “You don’t have to wait for 100-gigabit PAM-4 [ICs] to be manufactured in high volume.”
Urricariet says the IEEE is considering developing an extended LR8 standard with a 40km reach but such distances could also be addressed using inexpensive coherent technology.
Finisar’s design achieves the extended range using the same components as its LR8 module - directly modulated DFB lasers and PIN photodetectors. “There is plenty of margin with that [LR8 design],” says Urricariet. This suggests Finisar picked the best performing DFBs and PINs for the eLR8 design.
The QSFP-DD 10km LR8 design is sampling now, with general availability from the first half of 2019.
Flextune
Configuring DWDM links can be likened to two groups of people separated in a wood at night. Each individual has a flashlight and is tasked with finding a counterpart from the second group, a process repeated until everyone is paired.
Setting up DWDM links is comparable to telling each individual the exact path to take to find their counterpart. The Flextune technology that Finisar has developed can be viewed as giving each individual the confidence to stride out - sweeping their flashlights as they go - till they find a counterpart.
Currently, setting up a DWDM link requires coordination between a field engineer and network operations staff. Each tunable transceiver that is plugged into a port is told which wavelength to tune to. The system itself may tell the transceiver the wavelength to use or a field engineer programs each transceiver before it is plugged into the platform.
Equally, the transceiver output fibre must be connected to the right optical multiplexer and demultiplexer (mux-demux) port, as do the transceivers at the link’s other end.
The result is a time-consuming process that is prone to human error.
With Flextune, the tunable transceivers are plugged into the equipment’s ports and connected to the mux-demux’s ports. “It does not matter which port,” says Urricariet. “The transceivers search for each other and self-configure to the right wavelength.”
Each Flextune-enabled transceiver operates independently of the transceiver at the other end; there is no master-slave arrangement, says Urricariet, although a master-slave arrangement can be used if requested.
The mux-demux must also be a blocking architecture for Flextune to work. “If the mux-demux does not block the other wavelengths on each port, then you have a mess,” says Urricariet. With such a mux-demux, the channels scanned are blocked until the transceiver’s output is passed to the right channel. Once the link is established, the two transceivers set permanently to that wavelength.
“It [the process] happens at both ends simultaneously and on all the ports,” says Urricariet. “The basic technique can self-tune up to 96 [DWDM] channels in around five minutes.”
Being able to tune independently of the host equipment means that the Flextune-enabled transceivers can also be sold directly to operators and plugged into any of their equipment.
Urricariet says Flextune promises welcome operational savings given DWDM’s increasing adoption in the access network with developments such as 5G fronthaul.
The basic technique can self-tune up to 96 [DWDM] channels in around five minutes
Flextune will also be used for metro and data centre interconnect applications, as well as connecting Remote PHY nodes being deployed in cable networks. “The Remote PHY is also a big focus for this type of feature,” says Urricariet.
Finisar demonstrated Flextune with its 10-gigabit tunable SFP+ modules that are now sampling. Flextune will also be adopted for its 25-gigabit SFP+ that will sample ‘very soon’, followed by coherent modules.
“We do have a CFP2-ACO module in production and other coherent products on our roadmap,” says Urricariet. “We will be looking to implement Flextune technology in these products as well.”
Google has started deployments of 2x200GbE
200 Gigabit Ethernet: a growing interim solution
Finisar also demonstrated two 200-gigabit modules. The QSFP56 implements the 2km FR4 specification. The 200-gigabit FR4 uses four coarse WDM (CWDM) wavelengths, each carrying a 50-gigabit PAM-4 signal.
Finisar has previously said it will develop 200-gigabit modules for the large-scale data centres interested in the technology as an interim solution before 400-gigabit modules ramp. Such an intermediate market for “one hyperscaler and maybe two” is sufficient to justify making 200-gigabit modules, says Urricariet.
Market research firm LightCounting has increased its forecast for 200 Gigabit Ethernet (GbE) modules due to interest from Facebook.
A presentation by Facebook at ECOC suggested that 400 GbE is far from being ready, says Vladimir Kozlov, CEO of LightCounting. “It looks like 200GbE is being considered now, but Facebook may change its mind again,” says Kozlov. “In the meantime, Google has started deployments of 2x200GbE [in an OSFP module] as planned.”
As with the 400-gigabit eLR8, Finisar also demonstrated an extended reach version of the 200-gigabit FR4 to achieve a 10km reach. “This is not to be confused with the 10km 200-gigabit LR4 that is a LAN-WDM grid based design,” says Urricariet. “The extended FR4 uses a CWDM grid.”
ITTRA
At OFC 2018 in March, Finisar unveiled its 32-gigabaud (Gbaud) integrated tunable transmitter and receiver assembly (ITTRA) that combines the optics and electronics required for an analogue coherent optics interface.
The ITTRA comprises a tunable laser, an optical amplifier, modulators, modulator drivers, coherent mixers, a photo-detector array and the accompanying TIAs. All the components of the 32Gbaud ITTRA are integrated within a gold box that is 70 percent smaller than the size of a CFP2 module. The integrated assembly also has a power consumption below 7.5W.
At ECOC, the company demonstrated its second ITTRA design operating at 64Gbaud to transmit a 400-gigabit wavelength using 16-ary quadrature amplitude modulation (16-QAM). Finisar would not detail the power consumption of the 64Gbaud ITTRA.
“The doubling of the speed to 64Gbaud will enable 400-gigabit DCO modules as well as 400ZR,” says Urricariet. Digital coherent optics (DCO) refers to coherent modules that integrate the optics and the coherent digital signal processor (DSP).
Samples and production of the 64Gbaud ITTRA are due in 2019.
Ciena to sell its own coherent modules
The systems vendor is expanding its offerings to include WaveLogic modem chips and coherent optical modules.
Ciena is developing its own coherent modules to sell to the telecom and datacom markets.
The system vendor has set up the Optical Microsystems Division business unit to promote its WaveLogic coherent modem technology to the marketplace. Until now it has licensed its WaveLogic Ai digital signal processor (DSP) to module makers Lumentum, NeoPhotonics and Oclaro. But now it is planning to sell its own coherent modules.
In a job advert for a head of sales channel development, Ciena says the Optical Microsystems Division's goal is ‘to develop and productize electro-optic components and modules for sale to global systems integrator customers to be incorporated in their products for sale to telecom and data network customers’.
And at the recent European Conference on Optical Communication (ECOC) held in Rome, a network equipment manufacturer said it was approached by Ciena enquiring if it was interested in buying coherent modules from the company.
Ciena would not comment when asked if it will sell its own coherent modules. Instead, the company pointed to statements it made during its fourth quarter 2017 earnings call that outlined the creation of the Optical Microsystems Division with the stated goal of generating $50 million annual revenues by year-end 2020.
[At ECOC], a network equipment manufacturer said it was approached by Ciena enquiring if it was interested in buying coherent modules from the company
Optical Microsystems Division
Until Ciena announced in early 2017 the licensing of its 400-gigabit WaveLogic Ai to Lumentum, NeoPhotonics and Oclaro, systems vendors kept their coherent DSPs in-house. And with good reason. These are the chips that power their leading optical platforms and enable product differentiation.
Ciena’s announcement at the time showed a willingness to pursue a different business model. By licensing its DSP to optical module makers, Ciena could break into important new markets such as China even though the move would benefit its competitors using its advanced DSP for their platforms.
But the market has changed since Ciena made the announcement and now the company is deciding how best to proceed, says Mike Genovese, managing director and senior equity research analyst at MKM Partners.
“At the time of the announcement it seemed there was a big opportunity selling the [coherent] modem into Chinese OEMs,” says Genovese. “But that seems less likely now because Chinese OEMs want to assemble their own modules out of components they buy and make.”
The result is that the opportunity has shifted to data centre interconnect. “But there are decisions that need to be made,” says Genovese. “For example, does Ciena want to make its modem product a [pluggable] 400ZR solution?”
It is a view shared by Sterling Perrin, principal analyst, optical networking and transport at Heavy Reading.
“It [the licensing of its DSP] was originally built around breaking into the China market. That strategy now looks must riskier than it did originally, so I’m certain they are looking at every alternative,” says Perrin. ”The main goal is to get the most return-on-investment on the money they put into building a WaveLogic generation, and using that money to fund the next generation of DSP investment.”
At the time of the announcement it seemed there was a big opportunity selling the [coherent] modem into Chinese OEMs. But that seems less likely now.
Pluggables are going to become an important opportunity for coherent technology, says Andrew Schmitt, founder and directing analyst at Cignal AI. Schmitt says the next stage of coherent’s development - what he calls the fourth generation of coherent - will be pluggable from the start and more standards-based than any wavelength-division multiplexing (WDM) pluggable that has preceded it.
“It will address a large portion of the overall market - not just cloud operator data centreinterconnect,” says Schmitt. “Equipment vendors will need to adjust their strategies as many standalone optical hardware applications will be displaced by pluggable coherent.”
Ciena also has all the required technologies. As well as its WaveLogic modem technology, it has high-speed optical component expertise that it gained with the 2016 acquisition of Teraxion’s photonics division. The Teraxion group had indium phosphide and silicon photonics technologies.
All change
The agreement between Ciena and the three optical module makers also included an option where future WaveLogic DSPs would be made available to the three for applications such as 400-gigabit pluggables.
NeoPhotonics says that Ciena’s general strategy of bringing its WaveLogic Ai technology to a larger market and application space has not changed.
Equipment vendors will need to adjust their strategies as many standalone optical hardware applications will be displaced by pluggable coherent
Is Ciena going straight to market with future WaveLogic-based modules?
“How the modules are marketed may follow different models in the future; there is always an evolution in business models as the market shifts,” says Ferris Lipscomb, NeoPhotonics’ vice president of marketing. “Our intention is to continue to be a partner and bring value to the Ciena Microsystems business wherever possible.”
Lumentum would not comment on what the status was regarding using future coherent DSPs, nor would it say whether Ciena is to sell its own modules. Lumentum did say that it has a close relationship with Ciena and that it continues to support partnership opportunities.
But the possibility of Ciena selling modules to the marketplace is not ruled out by Ciena’s third optical module partner, Oclaro.
Yves LeMaitre, chief strategy officer at Oclaro says that Ciena’s recent announcements could point to a new strategic direction. “At this point, it is unclear how they are going to do this,” he says. Oclaro also does not know yet if it will gain access to new WaveLogic designs.
LeMaitre views the options with Ciena’s coherent technology as part of a broader debate as to how systems vendors should adapt their business models in an environment of change brought about by software-defined networks and open design frameworks.
The fact that internet content providers purchase optics directly, as do certain service providers, creates a dilemma for the systems vendors. “How are they going to go to the market to address this?” says LeMaitre. “Are they going to rely on a partnership with module makers or are they going to address the market on their own?”
Oclaro says it remains ‘very interested’ in working with Ciena if it is willing to give the module maker access to future DSP designs for pluggables.
Intel targets 5G fronthaul with a 100G CWDM4 module
- Intel announced at ECOC that it is sampling a 10km extended temperature range 100-gigabit CWDM4 optical module for 5G fronthaul.
- Another announced pluggable module pursued by Intel is the 400 Gigabit Ethernet (GbE) parallel fibre DR4 standard.
- Intel, a backer of the CWDM8 MSA, says the 8-wavelength 400-gigabit module will not be in production before 2020.
Intel has expanded its portfolio of silicon photonics-based optical modules to address 5G mobile fronthaul and 400GbE.
Robert BlumAt the European Conference on Optical Communication (ECOC) being held in Rome this week, Intel announced it is sampling a 100-gigabit CWDM4 module in a QSFP form factor for wireless fronthaul applications.
The CWDM4 module has an extended temperature range, -20°C to +85°C, and a 10km reach.
“The final samples are available now and [the product] will go into production in the first quarter of 2019,” says Robert Blum, director of strategic marketing and business development at Intel’s silicon photonics product division.
Intel also announced it will support the 400GBASE-DR4, the IEEE’s 400 GbE standard that uses four parallel fibres for transmit and four for the receive path, each carrying a 100-gigabit 4-level pulse amplitude modulation (PAM-4) signal.
5G wireless
5G wireless will be used for a variety of applications. Already this year the first 5G fixed and mobile wireless services are expected to be launched. 5G will also support massive Internet of Things (IoT) deployments as well as ultra-low latency applications.
The next-generation wireless standard uses new spectrum that includes millimetre wave spectrum in the 24GHz to 40GHz region. Such higher frequency bands will drive small-cell deployments.
5G’s use of new spectrum, small cells and advanced air interface techniques such as multiple input, multiple output (MIMO) antenna technology is what will enable its greater data speeds and vastly expanded capacity compared to the current LTE cellular standard.
Source: Intel.
The 5G wireless standard will also drive greater fibre deployment at the network edge. And it is here where mobile fronthaul plays a role, linking the remote radio heads at the antennas with the centralised baseband controllers at the central office (see diagram). Such fronthaul links will use 25-gigabit and 100-gigabit links. “We have multiple customers that are excited about the 100-gigabit CWDM4 for these applications,” says Blum
Intel expects demand for 25-gigabit and 100-gigabit transceivers for mobile fronthaul to begin in 2019.
Intel is now producing over one million PSM4 and CWDM4 modules a year
Client-side modules
Intel entered the optical module market with its silicon photonics technology in 2016 with a 100-gigabit PSM4 module, quickly followed by a 100-gigabit CWDM4 module. Intel is now producing over one million PSM4 and CWDM4 modules a year.
Intel will provide customers with 400-gigabit DR4 samples in the final quarter of 2018 with production starting in the second half of 2019. This is when Intel says large-scale data centre operators will require 400 gigabits.
“The initial demand in hyperscale data centres for 400 gigabits will not be for duplex [fibre] but parallel fibre,” says Blum. “So we expect the DR4 to go to volume first and that is why we are announcing the product at ECOC.”
Intel says the advantages of its silicon photonics approach have already been demonstrated with its 100-gigabit PSM4 module. One is the optical performance resulting from the company’s heterogeneous integration technique combining indium-phosphide lasers with silicon photonics modulators on the one chip. Another advantage is scale using Intel’s 300mm wafer-scale manufacturing.
Intel says demand for the 500m-reach DR4 module to go hand-in-hand with that for the 100-gigabit single- wavelength DR1, given how the DR4 will also be used in breakout mode to interface with four DR1 modules.
“We don’t see the DR1 standard competing or replacing 100-gigabit CWDM4,” says Blum. “The 100-gigabit CWDM4 is now mature and at a very attractive price point.”
Intel is a leading proponent of the CWDM8 MSA, an optical module design based on eight wavelengths, each a 50 gigabit-per-second (Gbps) non-return-to-zero (NRZ) signal. The CWDM8 MSA was created to fast-track 400 gigabit interfaces by avoiding the wait for 100-gigabit PAM-4 silicon.
When the CWDM8 MSA was launched in 2017, the initial schedule was to deploy the module by the end of this year. Intel also demonstrated the module working at the OFC show held in March.
Now, Intel expects production of the CWDM8 in 2020 and, by then, other four-wavelength solutions using 100-gigabit PAM-4 silicon such as the 400G-FR4 MSA will be available.
“We just have to see what the use case will be and what the timing will be for the CWDM8’s deployment,” says Blum.
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.”
COBO issues industry’s first on-board optics specification
- COBO modules supports 400-gigabit and 800-gigabit data rates
- Two electrical interfaces have been specified: 8 and 16 lanes of 50-gigabit PAM-4 signals.
- There are three module classes to support designs ranging from client-slide multi-mode to line-side coherent optics.
- COBO on-board optics will be able to support 800 gigabits and 1.6 terabits once 100-gigabit PAM-4 electrical signals are specified.
Source: COBO
Interoperable on-board optics has moved a step closer with the publication of the industry’s first specification by the Consortium for On-Board Optics (COBO).
COBO has specified modules capable of 400-gigabits and 800-gigabits rates. The designs will also support 800-gigabit and 1.6-terabit rates with the advent of 100-gigabit single-lane electrical signals.
“Four hundred gigabits can be solved using pluggable optics,” says Brad Booth, chair of COBO and principal network architect for Microsoft’s Azure Infrastructure. “But if I have to solve 1.6 terabits in a module, there is nothing out there but COBO, and we are ready.”
Origins
COBO was established three years ago to create a common specification for optics that reside on the motherboard. On-board optics is not a new technology but until now designs have been proprietary.
I have to solve 1.6 terabits in a module, there is nothing out there but COBO, and we are ready
Brad BoothSuch optics are needed to help address platform design challenges caused by continual traffic growth.
Getting data on and off switch chips that are doubling in capacity every two to three years is one such challenge. The input-output (I/O) circuitry of such chips consumes significant power and takes up valuable chip area.
There are also systems challenges such as routing the high-speed signals from the chip to the pluggable optics on the platform’s faceplate. The pluggable modules also occupy much of the faceplate area and that impedes the air flow needed to cool the platform.
Using optics on the motherboard next to the chip instead of pluggables reduces the power consumed by shortening the electrical traces linking the two. Fibre rather than electrical signals then carries the data to the faceplate, benefiting signal integrity and freeing faceplate area for the cooling.
Specification 1.0
COBO has specified two high-speed electrical interfaces. One is 8-lanes wide, each lane being a 50-gigabit 4-level pulse-amplitude modulation (PAM-4) signal. The interface is based on the IEEE’s 400GAUI-8, the eight-lane electrical specification developed for 400 Gigabit Ethernet.
The second electrical interface is a 16-lane version for an 800-gigabit module. Using a 16-lane design reduces packaging costs by creating an 800-gigabit module instead using two separate 400-gigabit ones. Heat management is also simpler with one module.
There are also systems benefits using an 800-gigabit module.“As we go to higher and higher switch silicon bandwidths, I don’t have to populate as many modules on the motherboard,” says Booth.
The latest switch chips announced by several companies have 12.8 terabits of capacity that will require 32, 400-gigabit on-board modules but only 16, 800-gigabit ones. Fewer modules simplify the board’s wiring and the fibre cabling to the faceplate.
Designers have a choice of optical formats using the wider-lane module, such as 8x100 gigabits, 2x400 gigabits, and even 800 gigabits.
COBO has tested its design and shown it can support a 100-gigabit electrical interface. The design uses the same connector as the OSFP pluggable module.
“In essence, with an 8-lane width, we could support an 800-gigabit module if that is what the IEEE decides to do next,” says Booth. “We could also support 1.6 terabits if that is the next speed hop.”
It is very hard to move people from their standard operating model to something else until there is an extreme pain point
Form factor and module classes
The approach chosen by COBO differs from proprietary on-board optics designs in that the optics is not mounted directly onto the board. Instead, the COBO module resembles a pluggable in that once placed onto the board, it slides horizontally to connect to the electrical interface (see diagram, top).
A second connector in the middle of the COBO module houses the power, ground and control signals. Separating these signals from the high-speed interface reduces the noise on the data signals. In turn, the two connectors act as pillars supporting the module.
The robust design allows the modules to be mounted at the factory such that the platform is ready for operation once delivered at a site, says Booth.
COBO has defined three module classes that differ in length. The shortest Class A modules are used for 400-gigabit multi-mode interfaces while Class B suits higher-power IEEE interfaces such as 400GBASE-DR4 and the 100G Lambda MSA’s 400G-FR4.
The largest Class C module is for the most demanding and power-hungry designs such as the coherent 400ZR standard. “Class C will be able to handle all the necessary components - the optics and the DSP - associated with that [coherent design],” says Booth.
The advantage of the on-board optics is that it is not confined to a cage as pluggables are. “With an on-board optical module, you can control the heat dissipation by the height of the heat sink,” says Booth. “The modules sit flatter to the board and we can put larger heat sinks onto these devices.”
We realised we needed something as a stepping stone [between pluggables and co-packaged optics] and that is where COBO sits
Next steps
COBO will develop compliance-testing boards so that companies developing COBO modules can verify their designs. Booth hopes that by the ECOC 2018 show to be held in September, companies will be able to demonstrate COBO-based switches and even modules.
COBO will also embrace 100-gigabit electrical work being undertaken by the OIF and the IEEE to determine what needs to be done to support 8-lane and 16-lane designs. For example, whether the forward-error correction needs to be modified or whether existing codes are sufficient.
Booth admits that the industry remains rooted to using pluggables, while the move to co-packaged optics, where the optics and the chip are combined in the same module - remains a significant hurdle, both in terms of packaging technology and the need for vendors to change their business models to build such designs.
“It is very hard to move people from their standard operating model to something else until there is an extreme pain point,” says Booth.
Setting up COBO followed the realisation that a point would be reached when faceplate pluggables would no longer meet demands while in-packaged technology would not be ready.
“We realised we needed something as a stepping stone and that is where COBO sits,” says Booth.
Further information
For information on the COBO specification, click here.