NeoPhotonics’ growing 400G coherent pluggable portfolio
NeoPhotonics has unveiled its first two 400-gigabit coherent pluggable modules that support the OIF’s 400ZR coherent standard and extended ZR+ modes.
The company has delivered samples of its ClearLight CFP2-DCO module for trials. The CFP2-DCO supports 400ZR, metro, and long-haul optional transmissions.
NeoPhotonics has also delivered to a hyperscaler the first samples of a 400-gigabit OSFP pluggable that supports 400ZR and 400ZR+.
Both modules use Inphi’s latest Canopus 7nm CMOS coherent digital signal processor (DSP) chip.
Module types
The OIF has developed the 400ZR standard to enable 400-gigabit signals to be sent between switches or routers in data centres up to 120km apart.
The main three pluggable modules earmarked for 400ZR are the QSFP-DD, OSFP and CFP2-DCO.
These modules differ in size and power envelope, ranging from the QSFP-DD, which is the most compact and has the smallest power envelope, to the CFP2-DCO module which supports the highest power and size.
It is the two client-side module form factors – the QSFP-DD and the OSFP – that will be mainly used for 400ZR.
“The CFP2 has more of a power envelope available so it tends to be used for longer reach applications,” says Ferris Lipscomb, vice president of marketing at NeoPhotonics.
These applications include specialist data-centre-interconnect applications and the metro and long-haul needs of the telecom operators.
400G CFP2-DCO
NeoPhotonics’ ClearLight CFP2-DCO uses an extension of a fibre’s C-band spectrum, what Huawei calls the Super C-band while NeoPhotonics refers to its implementation as C++.
The Super C-band covers 6THz of the spectrum compared to the standard C-band’s 4THz. The extended band can fit 120, 50GHz-wide channels or 80, 75GHz-wide channels.
NeoPhotonics can send 64-gigabaud (GBd), 400-gigabit signals over a 75GHz channel such that using ClearLight CFP2-DCO modules, 32 terabits can be sent overall.
The CFP2-DCO module uses NeoPhotonics’s ultra narrow-band line-width tunable laser that has had its tuning range extended to span the Super C-band. NeoPhotonics also uses its 64GBd intradyne coherent receiver (ICR) and coherent driver modulator.
The ClearLight CFP2-DCO can also send 400-gigabit signals over distances greater than 400ZR’s 120km. In addition, the module supports 200-gigabit transmissions over greater distances.
Sending a 200-gigabit at 64GBd using a 75GHz channel and quadrature phase-shift keying (QPSK) modulation, an optical signal-to-noise ratio (OSNR) of under 14dB is needed. Alternatively, using a 50GHz channel at 32GBd and 16-ary quadrature amplitude modulation (16-QAM), the OSNR is 16dB.
“With these [decibel] numbers, lower is better,” says Lipscomb. “You can go further with 64 gigabaud and QPSK; it’s 2dB better.”
Lipscomb says one use case for the 400-gigabit CFP2-DCO promises significant volumes: “The Super C-band has been used for deployments particularly by the Chinese carriers where they want to get more channels down a fibre.”
OSFP
NeoPhotonics has also unveiled its ClearLight OSFP module that enables the 400ZR standard and 400-gigabit transmissions for metro.
The module incorporates NeoPhotonics’s nano integrated tunable laser assembly (Nano-ITLA) and its silicon photonics-based coherent optical sub-assembly (COSA) that integrates the coherent receiver and modulator driver functions.
The OSFP tunes over 75GHz- or 100GHz-spaced channels, enabling 85 and 64 channels, respectively, as specified by the OIF. The OSFP also supports longer metro reaches at 400 gigabits.
NeoPhotonics also makes arrayed waveguide gratings (AWG) suited for 64GBd and 75GHz channel spacings that both modules support. “You need broader passbands and different channel spacings for 64 gigabaud,” says Lipscomb.
ZR+ interop?
Lipscomb is not a proponent of enforcing standardisation for the ZR+ extended modes, as has been done with 400ZR, despite the resulting lack of interoperability between optical modules from different vendors.
“There will always be the temptation in cases where you need it, to give up interoperability for increased [optical] performance,” he says.
Data centre interconnect drives coherent
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NeoPhotonics announced at OFC a high-speed modulator and intradyne coherent receiver (ICR) that support an 800-gigabit wavelength
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It also announced limited availability of its nano integrable tunable laser assembly (nano-ITLA) and demonstrated its pico-ITLA, an even more compact silicon photonics-based laser assembly
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The company also showcased a CFP2-DCO pluggable
NeoPhotonics unveiled several coherent optical transmission technologies at the OFC conference and exhibition held in San Diego last month.
“There are two [industry] thrusts going on right now: 400ZR and data centre interconnect pizza boxes going to even higher gigabits per wavelength,” says Ferris Lipscomb, vice president of marketing at NeoPhotonics.
Ferris Lipscomb
The 400ZR is an interoperable 400-gigabit coherent interface developed by the Optical Internetworking Forum (OIF).
Optical module makers are developing 400ZR solutions that fit within the client-side QSFP-DD and OSFP pluggable form factors, first samples of which are expected by year-end.
800-gigabit lambdas
Ciena and Infinera announced in the run-up to OFC their latest coherent systems - the WaveLogic 5 and ICE6, respectively - that will support 800-gigabit wavelengths. NeoPhotonics announced a micro intradyne coherent receiver (micro-ICR) and modulator components that are capable of supporting such 800-gigabit line-rate transmissions.
NeoPhotonics says its micro-ICR and coherent driver modulator are class 50 devices that support symbol rates of 85 to 90 gigabaud required for such a state-of-the-art line rate.
The OIF classification defines categories for devices based on their analogue bandwidth performance. “With class 20, the 3dB bandwidth of the receiver and the modulator is 20GHz,” says Lipscomb. “With tricks of the trade, you can make the symbol rate much higher than the 3dB bandwidth such that class 20 supports 32 gigabaud.” Thirty-two gigabaud is used for 100-gigabit and 200-gigabit coherent transmissions.
Class 50 refers to the highest component performance category where devices have an analogue bandwidth of 50GHz. This equates to a baud rate close to 100 gigabaud, fast enough to achieve data transmission rates exceeding a terabit. “But you have to allow for the overhead the forward-error correction takes, such that the usable data rate is less than the total,” says Lipscomb (see table).
Source: Gazettabyte, NeoPhotonics
Silicon photonics-based COSA
NeoPhotonics also announced a 64-gigabaud silicon photonics-based coherent optical subassembly (COSA). The COSA combines the receiver and modulator in a single package that is small enough to fit within a QSFP-DD or OSFP pluggable for applications such as 400ZR.
Last year, the company announced a similar COSA implemented in indium phosphide. In general, it is easier to do higher speed devices in indium phosphide, says Lipscomb, but while the performance in silicon photonics is not quite as good, it can be made good enough.
“It [silicon photonics] is now stretching certainly into the Class 40 [that supports 600-gigabit wavelengths] and there are indications, in certain circumstances, that you might be able to do it in the Class 50.”
Lipscomb says NeoPhotonics views silicon photonics as one more material that complements its indium phosphide, planar lightwave circuit and gallium arsenide technologies. “Our whole approach is that we use the material platform that is best for a certain application,” says Lipscomb.
In general, coherent products for telecom applications take time to ramp in volumes. “With the advent of data centre interconnect, the volume growth is much greater than it ever has been in the past,” says Lipscomb.
NeoPhotonics’ interested in silicon photonics is due to the manufacturing benefits it brings that help to scale volumes to meet the hyperscalers’ requirements. “Whereas indium phosphide has very good performance, the infrastructure is still limited and you can’t duplicate it overnight,” says Lipscomb. “That is what silicon photonics does, it gives you scale.”
NeoPhotonics also announced the limited availability of its nano integrable tunable laser assembly (nano-ITLA). “This is a version of our external cavity ITLA that has the narrowest line width in the industry,” says Lipscomb.
The nano-ITLA can be used as the source for Class 50, 800-gigabit systems and current Class 40 600 gigabit-per-wavelength systems. It is also small enough to fit within the QDFP-DD and OSFP client-side modules for 400ZR designs. “It is a new compact laser that can be used with all those speeds,” says Lipscomb.
NeoPhotonics also showed a silicon-photonics based pico-ITLA that is even smaller than the nano-ITLA.“The [nano-ITLA’s] optical cavity is now made using silicon photonics so that makes it a silicon photonics laser,” says Lipscomb.
Instead of having to assemble piece parts using silicon photonics, it can be made as one piece. “It means you can integrate that into the same chip you put your modulator and receiver on,” says Lipscomb. “So you can now put all three in a single COSA, what is called the IC-TROSA.” The IC-TROSA refers to an integrated coherent transmit-receive optical subassembly, defined by the OIF, that fits within the QSFP-DD and OSFP.
Despite the data centre interconnect market with its larger volumes and much faster product uptakes, indium phosphide will still be used in many places that require higher optical performance. “But for bulk high-volume applications, there are lots of advantages to silicon photonics,” says Lipscomb.
400ZR and 400ZR+
A key theme at this year’s OFC was the 80km 400ZR. Also of industry interest is the 400ZR+, not an OIF specification but an interface that extends the coherent range to metro distances.
Lipscomb says that the initial market for the 400ZR+ will be smaller than the 400ZR, while the ZR+’s optical performance will depend on how much power is left after the optics is squeezed into a QSFP-DD or OSFP module.
“The next generation of DSP will be required to have a power consumption low enough to do more than ZR distances,” he says. “The further you go, the more work the DSP has to do to eliminate the fibre impairments and therefore the more power it will consume.”
Will not the ZR+ curtail the market opportunity for the 400-gigabit CFP2-DCO that is also aimed at the metro?
“It’s a matter of timing,” says Lipscomb. “The advantage of the 400-gigabit CFP2-DCO is that you can almost do it now, whereas the ZR+ won’t be in volume till the end of 2020 or early 2021.”
Meanwhile, NeoPhotonics demonstrated at the show a CFP2-DCO capable of 100-gigabit and 200-gigabit transmissions.
NeoPhotonics has not detailed the merchant DSP it is using for its CFP2-DCO except to say that it working with ‘multiple ones’. This suggests it is using the merchant coherent DSPs from NEL and Inphi.
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.”
NeoPhotonics samples its first CFP-DCO products
The company has announced two such CFP Digital Coherent Optics (CFP-DCO) modules: a 100 gigabit-per-second (Gbps) module and a dual-rate 100Gbps and 200Gbps one.
“Our rationale [for entering the CFP-DCO market] is we have all the optical components and the [merchant coherent] DSPs are now becoming available,” says Ferris Lipscomb (pictured), vice president of marketing at NeoPhotonics. “It is possible to make this product without developing your own custom DSP, with all the expense that entails.”
-DCO versus -ACO
The pluggable transceiver line-side market is split between Digital Coherent Optics and Analog Coherent Optics (ACO) modules.
Optical module makers are already supplying the more compact CFP2 Analog Coherent Optics (CFP2-ACO) transceivers. The CFP2-ACO integrates the optics only, with the accompanying coherent DSP-ASIC chip residing on the line card. The CFP2-ACO suits system vendors that have their own custom DSP-ASICs and can offer differentiated, higher-transmission performance while choosing the optics in a compact pluggable module from several suppliers.
In contrast, the CFP-DCO suits more standard deployments, and for those end-customers that do not want to be locked into a single vendor and a proprietary DSP. The -DCO is also easier to deploy. In China, currently undertaking large-scale 100-gigabit optical transport deployments, operators want a module that can be deployed in the field by a relatively unskilled technician. Deploying an ACO requires an engineer to perform the calibration due to the analogue interface between the module and the DSP, says NeoPhotonics.
The DCO also suits those systems vendors that do not have their own DSP and do not want to source a merchant coherent DSP and implement the analogue integration on the line card.
Our rationale [for entering the CFP-DCO market] is we have all the optical components and the [merchant coherent] DSPs are now becoming available
One platform, two products
The two announced ClearLight CFP-DCO products are a 100 gigabit-per-second (Gbps) module implemented using polarisation multiplexing, quadrature phase-shift keying modulation (PM-QPSK), and a module that supports both 100Gbps and 200Gbps using PM-QPSK and 16 quadrature amplitude modulation (PM-16QAM), respectively.
The two modules share the same optics and DSP-ASIC. Where they differ is in the software loaded onto the DSP and the host interface used. The lower-speed module has a 4 by 25-gigabit interface whereas the 200-gigabit CFP-DCO uses an 8 by 25-gigabit-wide interface. “The 100-gigabit CFP-DCO plugs into existing client-side slots whereas the 200-gigabit CFPs have to plug into custom designed equipment slots,” says Lipscomb.
The 100-gigabit CFP-DCO has a reach of 1,000km plus and has a power consumption under 24W. Lipscomb points out that the actual specs including the power consumption are negotiated on a customer-by-customer basis. The 200-gigabit CFP-DCO has a reach of 500km.
NeoPhotonics says it is using a latest-generation 16nm CMOS merchant DSP. NTT Electronics (NEL) and Clariphy have both announced 16nm CMOS coherent DSPs.
“We are designing to be able to second-source the DSP,” says Lipscomb. “There are currently only two merchant suppliers but there are others that have developments but are not yet at the point where they would be in the market.”
The CFP-DCO modules also support flexible grid that can fit a carrier within the narrower 37.5GHz channel to increase overall transmission capacity sent across a fibre’s C-band.
NeoPhotonics’s 100Gbps CFP-DCO is already sampling and it expected to be generally available in mid-2017, while the 200Gbps CFP-DCO is expected to be available one-quarter later.
“For 200-gigabit, you need to have customers building slots,” says Lipscomb. “For 100-gigabit, there are lots of slots available that you can plug into; 200-gigabits will take a little bit longer.”
NeoPhotonics’ CFP-DCO delivers the line rate used by the Voyager white box packet optical switch being developed as part of the Telecom Infra Project backed by Facebook and ten operators including Deutsche Telekom and SK Telecom. But the one-rack-unit Voyager packet optical platform uses four 5"x7" modules not pluggable CFP-DCOs to achieve the total line rate of 800Gbps.
Roadmap
NeoPhotonics is developing coherent module designs that will use higher baud rates than the standard 32-35 gigabaud (Gbaud), such as 45Gbaud and 64Gbaud.
The company also plans to develop a CFP2-DCO. Such a module is expected around 2018 once lower-power DSP-ASICs become available that can fit within the 12W power envelope of the CFP2. Such merchant DSP-ASICs will likely be implemented in a more advanced CMOS process such as 12nm or even 7nm.
Acacia Communications is already sampling a CFP2-DCO. Acacia designs its own silicon photonics-based optics and the coherent DSP-ASIC.
NeoPhotonics is also considered future -ACO designs beyond the CFP2 such as the CFP8, the 400-gigabit OSFP form factor and even the CFP4. “We are studying it but we don't know yet which directions things are going to go,” says Lipscomb.
Corrected on Dec 22nd. The Voyager box does not use pluggable CFP-DCO modules.
NeoPhotonics showcases a CFP2-ACO roadmap to 400G
The company demonstrated the CFP2-ACO module transmitting at 100 gigabit using polarisation multiplexed, quadrature phase-shift keying (PM-QPSK) modulation at the recent OFC show. The line-side module is capable of transmitting over 1,000km and also supports PM-16QAM that doubles capacity over metro network distances.
Ferris LipscombThe CFP2-ACO is a Class 3 design: the control electronics for the modulator and laser reside on the board, alongside the coherent DSP-ASIC chip.
At OFC, NeoPhotonics also demonstrated single-wavelength 400-gigabit transmission using more advanced modulation and a higher symbol rate, and a short-reach 100-gigabit link for inside the data centre using 4-level pulse-amplitude modulation (PAM4) signalling.
Roadmap to 400 gigabit
One benefit of the CFP2-ACO is that the pluggable module can be deployed only when needed. Another is that the optics will work with coherent DSP-ASICs for different systems vendors and merchant chip suppliers.
“After a lot of technology-bragging about the CFP2-ACO, this is the year it is commercial,” says Ferris Lipscomb, vice president of marketing at NeoPhotonics.
Also demonstrated were the components needed for a next-generation CFP2-ACO: NeoPhotonics’ narrow line-width tunable laser and its higher-bandwidth integrated coherent receiver. To achieve 400 gigabit, 32-QAM and a 45 gigabaud symbol rate were used.
Traditional 100-gigabit coherent uses a 32-gigabaud symbol rate. That combined with QPSK and the two polarisations results in a total bit rate of 2 polarisations x 2bits/symbol x 32 gigabaud or 128 gigabits: a 100-gigabit payload and the rest overhead bits. Using 32-QAM instead of QPSK increases the number of bits encoded per symbol from 2 to 5, while increasing the baud rate from 32 to 45 gigabaud adds a speed-up factor of 1.4. Combining the two, the resulting bit rate is 45 gigabaud x 5bits/symbol x 2 polarisations or 450 gigabit overall.
After a lot of technology-bragging about the CFP2-ACO, this is the year it is commercial
Using 32-QAM curtails the transmission distance to 100km due to the denser constellation but such distances are suited for data centre interconnect applications.
“That was the demo [at OFC] but the product is also suitable for metro distances of 500km using 16-QAM and long-haul of 1,000km using 200 gigabit and 8-QAM,” says Lipscomb.
PAM4
The PAM4 demonstration highlighted NeoPhotonics’ laser and receiver technology. The company showcased a single-wavelength link running at 112 gigabits-per-second using its 56Gbaud externally modulated laser (EML) with an integrated driver. The PAM4 link can span 2km in a data centre.
“What is not quite ready for building into modules is the [56Gbaud to 112 gigabit PAM4] DSP, which is expected to be out in the middle to the second half of the year,” says Lipscomb. The company will develop its own PAM4-based optical modules while selling its laser to other module makers.
Lipscomb says four lanes at 56 gigabaud using PAM4 will deliver a cheaper 400-gigabit solution than eight lanes, each at 25 gigabaud.
Silicon Photonics
NeoPhotonics revealed that it is supplying new 1310nm and 1550nm distributed feedback (DFB) lasers to optical module players that are using silicon photonics for their 100-gigabit mid-reach transceivers. These include the 500m PSM-4, and the 2km CWDM4 and CLR4.
Lipscomb says the benefits of its lasers for silicon photonics include their relatively high output power - 40 to 60mW - and the fact that the company also makes laser arrays which are useful for certain silicon photonics applications.
NeoPhotonics’ laser products have been for 100-gigabit modules with reaches of 2km to 10km. “Silicon photonics is usually used for shorter reaches of a few hundred meters,” says Lipscomb. “This new product is our first one aimed at the short reach data centre market segment.”
“Our main products have been for 100-gigabit modules for the longer reaches of 2km to 10km,” says Lipscomb. “Silicon photonics is usually used for shorter reaches of a few hundred meters, and this new [laser] product is our first one aimed at the short reach data centre market segment."
The company says it has multiple customer engagements spanning various wavelength plans and approaches for Nx100-gigabit data centre transceiver designs. Mellanox Technologies is one vendor using silicon photonics that NeoPhotonics is supplying.
NeoPhotonics to expand its tunable laser portfolio
Part 1: Tunable lasers
NeoPhotonics will become the industry's main supplier of narrow line-width tunable lasers for high-speed coherent systems once its US $17.5 million acquisition of Emcore's tunable laser business is completed. Gazettabyte spoke with Ferris Lipscomb of NeoPhotonics about Emcore's external cavity laser and the laser performance attributes needed for metro and long haul.
Key specifications and attributes of Emcore's external cavity laser and NeoPhotonics's DFB laser array. Source: NeoPhotonics.
Emcore and NeoPhotonics are leading suppliers of tunable lasers for the 100 Gigabit coherent market, according to market research firm Ovum. NeoPhotonics will gain Emcore's external cavity laser (ECL) on the completion of the deal, expected in January. The company will also gain Emcore's integrable tunable laser assembly (ITLA), micro ITLA, tunable XFP transceiver, tunable optical sub-assemblies, and 10, 40, 100 and 400 Gig integrated coherent transmitter products.
Emcore's ECL has a long history. Emcore acquired the laser when it bought Intel's optical platform division for $85 million in 2007, while Intel acquired the laser from New Focus in 2002 in a $50 million deal. Meanwhile, NeoPhotonics bought Santur's distributed feedback (DFB) tunable laser array in 2011 in a $39 million deal.
The two lasers satisfy different needs: Emcore's is suited for high-speed long distance transmission while NeoPhotonics's benefits metro and intermediate distances.
The Emcore laser uses mirrors and optics external to the gain medium to create the laser's relatively long cavity. This aids high-performance coherent systems as it results in a laser with a narrow line-width. Coherent detection uses a mixing technique borrowed from radio where an incoming signal is recovered by compared it with a local oscillator or tone. "The narrower the line-width, the more pure that tone is that you are comparing it to," says Lipscomb.
Source: NeoPhotonics
A narrower line-width also means less digital signal processing (DSP) is needed to resolve the ambiguity that results from that line-width, says Lipscomb: "And the more DSP power can be spent on either compensating fibre impairments or going further [distances], or compensating the higher-order modulation schemes which require more DSP power to disentangle."
The ECL has a narrow line-width that is specified at under 100kHz. "It is probably closer to 20kHz," says Lipscomb. One of the laser's drawbacks is that its uses a mechanical tuning mechanism that is relatively slow. It also has a lower output power of 16dBm compared to NeoPhotonics's DFB laser array that is up to 18dBm.
The metro market for 100 Gig coherent will emerge in volume towards the end of 2015 or early 2016
In contrast, NeoPhotonics' DFB laser array, suited to metro and intermediate reach applications, has a wider line-width specified at 300kHz, although 200kHz is typical. The DFB design comprises multiple lasers integrated compactly. The laser design also uses a MEMS that results in efficient coupling and the higher - 18dBm - output power. "Using the MEMS structure, you can integrate the laser with other indium phosphide or silicon photonics devices," says Lipscomb. "That is a little bit harder to do with the Emcore device."
Source: NeoPhotonics
It is the compactness and higher power of the DFB laser array that makes it suited to metro networks. The higher output power means that one laser can be used for both transmission and the local oscillator used to recover the received coherent signal. "More power can be good if you can live with the broader line-width," says Lipscomb. "It reduces overall system cost and can support higher-order modulation schemes over shorter distances."
Market opportunities
NeoPhotonics' focus is on narrow line-width lasers for coherent systems operating at 100 Gigabit and greater speeds. Lipscomb says the metro market for 100 Gig coherent will emerge in volume towards the end of 2015 or early 2016. "The distance here is less and therefore less compensation is needed and a little bit more line-width is tolerable," he says. "Also cost is an issue and a more integrated product can have potentially a lower cost."
For long haul, and especially at transmission rates of 200 and 400 Gig, the demands placed on the DSP are considerable. This is where Emcore's laser, with is narrow line-width, is most suited.
System vendors are already investigating 400 Gig and above transmission speeds. "For the high-end, line-width is going to be a critical factor," says Lipscomb. "Whatever modulation schemes there are to do the higher speeds, they are going to be the most demanding of laser performance."
For Part 2: Is the tunable laser market set for an upturn? click here