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.”
Oclaro demonstrates flexible rate coherent pluggable module
- The CFP2 coherent optical module operates at 100 and 200 Gig
- Samples are already with customers, with general availability in the first half of 2015
- Oclaro to also make more CFP2 100GBASE-LR4 products
The CFP2 is not just used in metro/ regional networks but also in long-haul applications
Robert Blum
The advent of a pluggable CFP2, capable of multi-rate long-distance optical transmission, has moved a step closer with a demonstration by Oclaro. The optical transmission specialist showed a CFP2 transmitting data at 200 Gigabits-per-second.
The coherent analogue module demonstration, where the DSP-ASIC resides alongside rather than within the CFP2, took place at ECOC 2014 held in September at Cannes. Oclaro showcased the CFP2 to potential customers in March, at OFC 2014, but then the line side module supported 100 Gig only.
"What has been somewhat surprising to us is that the CFP2 is not just used in metro/ regional networks but also in long-haul applications," says Robert Blum, director of strategic marketing at Oclaro. "We are also seeing quite significant interest in data centre interconnect, where you want to get 400 Gig between sites using two CFP2s and two DSPs." Oclaro says that the typical distances are from 200km to 1,000km.
The CFP2 achieves 200 Gig using polarisation multiplexing, 16-quadrature amplitude modulation (PM-16-QAM) while working alongside ClariPhy's merchant DSP-ASIC. ClariPhy announced at ECOC that it is now shipping its 200 Gig LightSpeed-II CL20010 coherent system-on-chip, implemented using a 28nm CMOS process.
"One of the beauties of an analogue CFP2 is that it works with a variety of DSPs," says Blum. Other merchant coherent DSPs are becoming available, while leading long-haul optical equipment vendors have their own custom coherent DSPs.
Oclaro's CFP2, even when operating at 200 Gig, falls within the 12W module's power rating. "One of the things you need to have for 200 Gig is a linear modulator driver, and such drivers consume slightly more power [200mW] than limiting modulator drivers [used for 100 Gig only]," says Blum.
Oclaro will offer two CFP2 line-side variants, one with linear drivers and one using limiting ones. The limiting driver CFP2 will be used for 100 Gig only whereas the linear driver CFP2 supports 100 Gig PM-QPSK and 200 Gig PM-16-QAM schemes. "Some customers prefer the simplicity of a limiting interface; for the linear interface you have to do more calibration or set-up," says Blum. "Linear also allows you to do pre-emphasis of the signal path, from the DSP all the way to the modulator." Pre-emphasis is used to compensate for signal path impairments.
By consuming under 12W, up to eight line-side CFP2 interfaces can fit on a line card, says Blum, who also stresses the CFP2 has a 0dBm output power at 200 Gig. Achieving such an output power level means the 200 Gig signal is on a par with 100 Gig wavelengths. "When you launch a 200 Gig signal, you want to make sure that there is not a big difference between signals," says Blum.
To achieve the higher output power, the micro integrable tunable laser assembly (micro-iTLA) includes a semiconductor optical amplifier (SOA) with the laser, while SOAs are also added to the Mach–Zehnder modulator chip. "That allows us to compensate for some of the [optical] losses," says Blum.
Customers received first CFP2 samples in May, with the module currently at the design validation stage. Oclaro expects volume shipments to begin in the first half of 2015.
100 Gig and the data centre
Oclaro also announced at ECOC that it has expanded manufacturing capacity for its CFP2-based 100GBASE-LR4 10km-reach module.
One reason for the flurry of activity around 100 Gig mid-reach interfaces that span 500m-2km in the data centre is that the 100GBASE-LR4 module is relatively expensive. Oclaro itself has said it will support the PSM-4, CWDM4 and CLR4 Alliance mid-reach 100 Gig interfaces. So why is Oclaro expanding manufacturing of its CFP2-based 100GBASE-LR4?
It is about being pragmatic and finding the most cost-effective solution for a given problem
"There is no clear good solution to get 100 Gig over 500m or 2km right now," says Blum. "CFP2 is here, it is a mature technology and we have made improvements both in performance and cost."
Oclaro has improved its EML design such that the laser needs less cooling, reducing overall power dissipation. The accompanying electronic functions such as clock data recovery have also been redesigned using one IC instead of two such that the CFP2 -LR4's overall power consumption is below 8W.
Demand has been so significant, says Blum, that the company has been unable to meet customer demand. Oclaro expects that towards year-end, it will have increased its CFP2 100GBASE-LR4 manufacturing capacity by 50 percent compared to six months earlier.
"It is about being pragmatic and finding the most cost-effective solution for a given problem," says Blum. "There are other [module] variants that are of interest [to us], such as the CWDM4 MSA that offers a cost-effective way to get to 2km."
ECOC 2013 review - Part 1
Gazettabyte surveys some of the notable product announcements made at the recent European Conference on Optical Communication (ECOC) held in London.
Part 1: Highlights
- First CFP4 module demonstration from Finisar
- Acacia Communications unveils first 100 Gig coherent CFP
- Oplink announces a 100 Gig direct detection CFP
- Second-generation coherent components take shape
100 Gigabit pluggables
Finisar used the ECOC exhibition to demonstrate the first CFP4 optical module, the smallest of the CFP MSA family of modules. The first CFP4 supports the 100GBASE-SR4 standard comprising four electrical and four optical channels, each at 25 Gigabit-per-second (Gbps).
The CFP4 is a quarter of the width of the CFP while the CFP2 is about a half the CFP's width. The CFP4 thus promises to quadruple the faceplate port density compared to using the CFP. Finisar says the CFP4 does even better, supporting line cards with 3.6 Terabits of capacity.
"It is not just the [CFP4's] width but the length and height that are shorter," says Rafik Ward, vice president of marketing at Finisar. The CFP4s can be aligned in two columns - belly-to-belly - on the card, achieving 3.6Tbps, each row comprising 18 CFP4 modules.
We see the CFP4 as a necessity to continue to grow the 100 Gigabit Ethernet market
The CFP4 was always scheduled to follow quickly the launch of the CFP2, says Ward. But the availability of the CFP4 will be important for the MSA. Data centre switch vendor Arista Networks has said that the CFP2 was late to market, while Cisco Systems has developed the CPAK, its own CFP2 alternative. "We see it [the CFP4] as a necessity to continue to grow the 100 Gigabit Ethernet market," says Ward.
Other 100 Gigabit Ethernet (GbE) variants will follow in the CFP4 form factor such as the LR4 and SR10 and the 10x10GbE breakout variant. This raises the interesting prospect of requiring an “inverse gearbox” chip that will translate between the CFP4's four electrical channels and the SR10's 10 optical channels. "We are going to see a lot of design activity around CFP4 in 2014," says Ward.
Meanwhile, Acacia Communications unveiled the AC-100, the first 100 Gig coherent CFP module for metro and regional networks, that includes a digital signal processor (DSP) system-on-chip.
"The DSP can be programmed for different performance and power levels to achieve a range of distances," says Daryl Inniss, vice president and practice leader components at market research firm, Ovum.
Acacia Communications says a CFP-based coherent design provides carriers and content providers with a 100 Gig metro solution that is more economical than 10 Gig.
Oplink Communications announced a direct detection 100 Gig metro CFP at ECOC. The 4x28Gbps CFP uses MultiPhy's maximum likelihood sequence estimation (MLSE) algorithm implemented using its MP1100Q and MP1101Q ICs. The devices enhance the reach of the module and allows 10 Gig optical components to be used for the receive and transmit paths. "Oplink’s CFP is the first module to come to market with our devices inside," says Neal Neslusan, vice president of marketing and sales at MultiPhy.
There are now at least three vendors selling direct-detection 100Gbps modules, says Neslusan, with Oplink and Menara Networks, which has also announced a CFP product, joining Finisar.
MultiPhy is working with several additional companies and that one system vendor will come to market with a product using the company's chips in the coming months. The company is also working on a second-generation direct detection IC design. "We believe there is a compelling roadmap story for direct detection," says Neslusan.
Oclaro announced it is now shipping in volume its 10km 100GBASE-LR4 CFP2 supporting 100GbE and OTU4 (OTN) rates. Oclaro has demonstrated the CFP2 working with a Xilinx Virtex 7 FPGA. "If customers choose that combination of technology, we have already tested it for them and they can rely on those rates [100GbE and OTU4] working," says Per Hansen, vice president of product marketing, optical networks solutions at Oclaro.
JDSU also said that its CFP2 LR4 is nearing completion. "We are getting pretty close to releasing it," says Brandon Collings, chief technology officer, communications and commercial optical products at JDSU.
Ed Murphy, JDSU
The integrated transmit and receive optical sub-assembly (TOSA/ ROSA) designs for the CFP2 LR4 use hybrid integration.
"In this case it is not monolithic integration as it is in the case of the indium phosphide line side modules but hybrid integration taking advantage of our PLC (planar lightwave circuit) technology in combination with arrays of photo detectors or high speed EMLs (externally modulated lasers)," says Murphy.
JDSU has based its module roadmap on the CFP2 TOSA and ROSA designs. The designs are sufficiently integrated to also fit within the QSFP28 and CFP4 modules.
There may be tweaks to the chips to lower the power dissipation, says Murphy, but these will be minor variants on existing parts.
Coherent components
Several component makers discussed their latest compact designs for next-generation coherent transmission line cards and modules.
NeoPhotonics detailed its micro-ITLA narrow linewidth tunable laser (micro-ITLA) that occupies less than a third of the area of the existing ITLA design. The company also announced a small form factor intradyne coherent receiver (SFF-ICR), less than half the size of existing integrated coherent receivers (ICRs).
NeoPhotonics supplies components to module and system vendors, and says customer interest in the second-generation coherent components is for higher port count line cards. "Instead of 100 Gig on a line card, you can have 200 or 400 Gigabit on a line card," says Ferris Lipscomb, vice president of marketing at NeoPhotonics. Moving to pluggable module designs will be a follow-on development, but for now, the market is not quite ready, he says.
An integrated coherent transmitter for metro, combining a tunable laser and integrated indium phosphide modulator in a compact package is also offered by NeoPhotonics.
The laser has two outputs - one output is modulated for the transmission while the second output is a local oscillator source feeding the coherent receiver. About half of all 100Gbps designs use such a split laser source, says Lipscomb, rather than two separate lasers, one each for the transmitter and the receiver. "That means that one transponder can only transmit and receive the same wavelength and is a little less flexible but for cost reduction that is what people are doing," says Lipscomb.
Oclaro is now sampling to customers its next-generation indium phosphide-based coherent components. The company, also a supplier of coherent modules, says the components will enable CFP and CFP2 pluggable coherent transceivers. The pluggable modules are suited for use in metro and metro regional networks.
Oclaro's components include an integrated transmitter comprising an indium phosphide laser and modulator, and the SFF-ICR. Oclaro's micro-ITLA is in volume production and has an output power high enough to perform both the transmit and the local oscillator functions. The micro-ITLA is used for line cards, 5x7-inch and 4x5-inch MSAs module and CFP designs.
u2t Photonics is another company that is developing a SFF-ICR. The company gave a private demonstration at ECOC to its customers of its indium phosphide modulator for use with CFP and CFP2 modules. "We demonstrated technical feasibility; it is a prototype which shows the capability of indium phosphide technology," says Jens Fiedler, executive vice president sales and marketing at u2t Photonics.
u2t Photonics and Finisar both licensed 100Gbps coherent indium phosphide modulator technology developed at the Fraunhofer Heinrich-Hertz-Institute.
There are new coherent DSP chips coming out early next year
Also showcased was u2t's gallium arsenide modulator technology implementing 16-QAM (quadrature amplitude modulation) at ECOC, but the company has yet to announce a product.
JDSU also gave an update on its line side coherent components. It is developing an integrated transmitter - a laser with nested modulators - for coherent applications. "This work is underway as a technology for line side CFP and CFP2 modules," says Ed Murphy, senior director, communications and commercial optical products at JDSU.
The difference between the CFP and CFP2 coherent modules is that the DSP system-on-chip is integrated within the CFP. Acacia's AC-100 CFP is the first example of such a product. For the smaller CFP2, the DSP will reside on the line card.
"There are new DSP [chips] coming out early next year," says Robert Blum, director of product marketing for Oclaro's photonic components. The DSPs will require a power consumption no greater than 20W if the complete design - the DSP and optics - is to comply with the CFP's maximum power rating of 32W.
Pluggable coherent modules promise greater port densities per line card. The modules can also be deployed with traffic demand and, in the case of a fault, can be individually swapped rather than having to replace the line card, says Blum.
JDSU says two factors are driving the metro coherent market. One is the need for lower cost designs to meet metro's cost-sensitive requirements. The second is that the metro distances can use essentially the same devices for 16-QAM to support 200Gbps links as well as 100Gbps. "It is the same modulator structure; maybe a few of the specs are a bit tighter but you can think of it as the same device," says Murphy.
System vendors have trialled 200Gbps links but deployments are expected to start from 2014. The deployments will likely use lithium niobate modulators, says Murphy, but will be followed quickly by indium phosphide designs.
NeoPhotonics used ECOC to declare that it has now integrated the semiconductor optical component arm of Lapis Semiconductor which it acquired for $35.2 million in March 2013.
Ferris Lipscomb
The unit, known as NeoPhotonics Semiconductor GK, makes drivers and externally modulated lasers. "These are key technologies for high-speed 100 Gig and 400 Gig transmissions, both on the line side and on the client side," says Lipscomb.
NeoPhotonics, previously a customer of Lapis, decided to acquire the unit and benefit from vertical integration as it expands its 100 Gig and higher-speed coherent portfolio.
Owning the technology has cost and optical performance benefits, says Lipscomb. It enables the integration of a design on one chip, thereby avoiding interfacing issues.
Further reading:
Part 2, click here