ADVA and II-VI’s coherent partnership
- ADVA and II-VI have jointly developed a 100-gigabit coherent DSP
- Both companies plan to use the 2.0-2.5W, 7nm CMOS Steelerton DSP for a 100ZR QSFP28 module
- II-VI’s ASIC design team engineered the DSP while ADVA developed the silicon photonics-based optics.
ADVA and II-VI have joined forces to define a tiny coherent digital signal processor (DSP) that fits inside a QSFP28 optical module.
The Steelerton DSP can send a 100-gigabit dense wavelength-division multiplexing (DWDM) transmission over 80-120km, carrying wireless backhaul and access traffic.
“It is backhaul of broadband, it is backhaul of mobile, and it definitely moves outdoors,” says Christoph Glingener, CTO at ADVA.
The module also serves metro networks with its 300km reach using optical amplification.
II-VI and ADVA now join such established coherent players as Ciena, Huawei, Infinera, Nokia as well as Marvell, NEL, and Acacia, now part of Cisco.
Effect Photonics announced at OFC earlier this year its coherent market entry with its acquisition of the Viasat DSP team.
Motivation
ADVA says it entered the coherent DSP market after failing to find a design suited for backhaul, a coherent market that promises highest unit volumes.
Backhaul has become even more important market for ADVA given its merger with broadband equipment maker ADTRAN.
II-VI also notes how access rates are moving from 10 to 100 gigabits.
“We were looking to develop a DSP capable to target a market that is underserved and where we can differentiate. This analysis led us to the 100ZR with a purpose-built DSP solution” says John DeMott, vice president product management, coherent and tunable product lines at II-VI.
The 100-gigabit coherent market for access contrasts with 400-gigabit coherent that uses modules such as 400ZR and 400ZR+ to connect data centres.
ADVA did consider existing suppliers’ coherent DSPs but deemed them too big and power-hungry for this application. This is what led to the II-VI partnership.
“We found a partner in II-VI that was willing to do this, but to get to the required power envelopes, we needed a 7nm DSP,” says Glingener. “And 7nm CMOS technology is not cheap.“
II-VI has a staff of mixed-signal and ASIC engineers in Germany that designed the Steelerton chip.
The two firms now have their own 100-gigabit DSP and can start developing coherent product roadmaps.
Applications
The 100ZR module will be deployed at aggregation sites.
ADVA shows how the 100ZR module is used for edge aggregation (see diagram).
Another application is 100-gigabit data-centre interconnect (DCI) for enterprises; hyperscalers require 400 gigabit and higher rates for DCI.
II-VI says the DSP is suited for access and metro applications. The 100ZR module fits a wavelength in a 50GHz channel to enable 96 DWDM wavelengths across the C-band. The 100ZR module has a maximum reach of 300km when used with amplification.
“The 22dB loss budget supports up to 80km without in-line amplification and up to 300km with in-line amplification, limited by chromatic dispersion,” says DeMott.
II-VI highlights several use-cases for the 100ZR module.
One is IP-over-DWDM, connecting edge routers to an aggregation router (see diagram) or a muxponder. The aggregated 100-gigabit wavelengths are sent to a metro router using a 400-gigabit 400ZR+ coherent module. II-VI also has 400ZR+ modules.
Two factors dictate the 100ZR module design: power consumption and the form factor.
Even a module power consumption of 10W is too high for access. Also, the DSP and optics must fit inside a QSFP28 since this is a common form factor for access equipment uplinks.
The resulting DSP has a power consumption of 2.0-2.5W and the chip is a fifth the size of other 7nm coherent DSPs. The 100ZR QSFP28 module – the DSP and optics – consumes 5.0-5.5W.
The DSP is stripped down to its essential features to achieve the power target. For example, the DSP uses one modulation format only: dual-polarisation, quadrature phase-shift keying (DP-QPSK).
“You de-feature the DSP down to a level that you can meet the power envelope, and it is not that complicated anymore,” says Glingener.
ADVA developed the silicon photonics analogue front end for the module that uses a single laser. To fit the DSP and the optics in a QSFP28 also proved an integration challenge.
The Steelerton DSP is taped out and both companies expect to have 100ZR prototype modules in the second half of this year.
What next
ADVA is planning a 100ZR+ module that will have enhanced optical performance that will be available in prototype form in early 2023.
ADVA’s coherent module interest remains broadband. Possible developments include a 5nm CMOS 200-gigabit DSP or a cheaper, more power-efficient, second-generation 100-gigabit design.
ADVA is also exploring concepts such as a parallel design, a 4x100G implementation.
Meanwhile, II-VI is looking at high-end coherent designs, which may include multiple sources for silicon photonics
“The next obvious steps are 800 gigabits and 1.6 terabits,” says DeMott. “There is a lot of [industry] activity, so those would be directions we’re considering.” II-VI has in-house optics for high-end coherent designs.
There will be a market for 800-gigabit coherent modules, says DeMott, but hyperscalers already are asking for 1.6-terabit designs.
“These are divergent DSPs,” says DeMott. “You can’t do a DSP that does 1.6 terabits, 800 gigabits and 400 gigabits; it’s either a 1.6-terabit or a 400/ 800-gigabit DSP design.”
OFC 2014 product round-up - Part 1
Part 1: Line-side technologies
Technologies for 100 Gigabit were prominent at this year's OFC conference and exhibition held in San Francisco earlier this month.
The transition to smaller pluggable modules – client-side CFP2, CFP4 and QSFP28 interfaces - was one 100 Gig trend, another was the first 100 Gig pluggable modules for metro and metro-regional networks. Acacia Communications detailed its low-power AC-100 CFP, while Oclaro demonstrated coherent optics in the smaller CFP2 pluggable module.
To fit within the CFP2, Oclaro has developed a transmitter that combines two tunable lasers (one being for the coherent receiver) and an indium phosphide modulator, and a micro intradyne coherent receiver (micro ICR).
Having 100 Gig coherent optics in a CFP2 will enable equipment makers to double the 100 Gig line ports on their platforms. The optics will also support polarisation multiplexed, 16-quadrature amplitude modulation (PM-16-QAM) and hence 200 Gig transmission. However, given the CFP2's limited power profile, the coherent DSP-ASIC will need to reside on the line card, external to the module. Oclaro says samples of its 'analogue CFP2' will be with customers from the second quarter of the year.
The same coherent optics will also be used for Oclaro's 100 Gig coherent CFP module. "If you combine the [transmitter and micro ICR] optics, you get the CFP2, and the power target is 12W," says Robert Blum, director, product management, 40 and 100 Gig line-side modules at Oclaro. "Combining the optics with a [coherent] DSP in the CFP, the power target is 32W, the highest CFP [power] class."
Oclaro's 100 Gig CFP will be available by year-end, coinciding with a new generation of merchant coherent DSP-ASIC designs. ClariPhy Communications is sampling its LightSpeed-II devices, implemented using a 28nm CMOS process, while NTT Electronics (NEL) is developing its next-generation DSP-ASIC, expected to use an even more advanced CMOS process.
Integrating the DSP chip and optics in a CFP simplifies a line card design and adds flexibility: the same CFP port can be used for line-side or client-side modules. But given that the coherent optics consumes 12W, the next-generation DSP-ASIC must consume no more than 18W typically, with the remaining 2W to accommodate the physical layer ICs, if the CFP's maximum power profile is not to be exceeded.
Acacia Communications' AC-100 coherent CFP module uses the company's DSP-ASIC and photonic integrated circuit (PIC) implemented using silicon photonics. The resulting 100 Gig CFP consumes 24-26W, well within the CFP's maximum 32W.
Meanwhile, Fujitsu Optical Components demonstrated all the components needed to make a 100 Gig coherent CFP, using its indium phosphide modulator to generate a 100 Gig polarisation multiplexed, quadrature phase-shift keying (PM-QPSK) signal, and a micro ICR.
Considering that the 5x7-inch Optical Internetworking Forum (OIF) multi-source agreement (MSA) 100 Gig transponder for long-haul consumes some 80W, with the DSP-ASIC alone consuming over half that, the advent of the coherent CFP and analogue CFP2 highlights the industry’s recent progress in shrinking the size and power consumption of coherent optics.
"Our focus long term is the CFP2. It is where we think the market is going to go in the next two years."
Ferris Lipscomb, NeoPhotonics
Coherent components
NeoPhotonics detailed an integrated coherent transmitter that combines a narrow-linewidth tunable laser and a PM-QPSK modulator in one package. The device joins NeoPhotonics' micro Integrable Tunable Laser Assembly (ITLA) and micro ICR that have already been announced. "These are the next generation, smaller form factor coherent optical components," says Ferris Lipscomb, vice president of marketing at NeoPhotonics. The transmitter supports PM-QPSK and PM-16-QAM such that it can be used for 100, 200 and even as an element to enable 400 Gig transmission.
The device is suited for line card, OIF MSA modules, and pluggable CFP and CFP2 designs. "Our focus long term is the CFP2," says Lipscomb. "It is where we think the market is going to go in the next two years." NeoPhotonics says its coherent devices has been sampling to customers and will be generally available in the second half of the year.
Oclaro announced that its micro ITLA, first detailed at ECOC 2013, now supports a flexible grid; the tunable laser's wavelength can be set independent of the ITU Grid spanning the C-band. Such a capability is required for advanced optical networks based on flexible-grid ROADMs and spectrally-efficient super-channels. "The flexible-grid micro ITLA gives peace of mind [to operators] even if it is not widely used yet," says Oclaro's Blum. The technology used for the micro ITLA is also used for Oclaro's CFP and CFP2 line side modules.
Fujitsu Optical Components announced a lithium niobate modulator that supports 100 Gig PM-QPSK and 400 Gig PM-xQAM signals. The new modulator has the same drive voltage as its existing 100 Gig lithium niobate modulator but is half the size. The company also announced an accompanying ICR that also supports 100 and 400 Gig transmissions in core networks. The company says both devices will be available from July.
Sumitomo Electric Industries detailed its micro ITLA at OFC. The micro ITLA uses a narrower line width laser and reduces power consumption by a fifth. The company also showcased a micro ICR that supports 100 and 200 Gig transmissions, and an indium phosphide based Mach-Zehnder modulator that is smaller and has lower power than a lithium niobate-based version.
Avago Technologies announced its micro ICR at OFC, a demonstration of Avago's broad component portfolio following its acquisition of CyOptics. Finisar was another company that showcased a new portfolio of high-speed optical components following its acquisition of u2t Photonics. These include indium phosphide-based Mach-Zehnder modulators and 100 Gig receivers and photodetectors.
Tunable SFP+
Both JDSU and Oclaro detailed their latest 10 Gigabit tunable SFP+ optical modules. Moving the tunable laser design from an XFP to the SFP+ has been a challenge, meeting the SFP+'s smaller dimensions and 1.5W power consumption.
Oclaro's latest tunable SFP+ now meets the 1.5W SFP+ specification. Oclaro says that to achieve the specification, it produced a more compact integrated laser Mach-Zehnder chip. Oclaro demonstrated the tunable SFP+ operating at 85oC. Beta samples of the tunable SFP+ are being shipped and the module will soon undergo qualification.
JDSU has had a tunable SFP+ product for over a year but its power consumption is 2W. The SFP+ length is also elongated by 4mm to fit the tunable laser. Now, JDSU has announced a revised design that no longer needs the extra 4mm and achieves a power consumption of 1.6W. "We will achieve the 1.5W specification in the near future," says Brandon Collings, JDSU's CTO for communications and commercial optical products.
"The reason why there is a lot of talk about hybrid EDFA-Raman in the industry is that it works very well with coherent."
Rafik Ward, Finisar
Pump lasers and hybrid amplifiers
JDSU also announced pump laser designs. The motivation for these latest pump products is the more demanding link budgets required for 100 Gig-and-greater transmission speeds while still achieving long-distance reaches.
JDSU announced Raman pump lasers for hybrid EDFA-Raman amplifiers. These are more power-efficient and cover the Raman pump wavelengths required, says JDSU: a 600mW output between 1425-1470nm and 550mW at 1470-1495nm. The company has also detailed higher-power 980nm pumps for EDFAs. "More power is almost always a good thing as it allows you a lot more design freedom and performance in your amp," says Collings.
Finisar demonstrated a hybrid EDFA-Raman amplifier for the first time. The hybrid amp is capable of spanning 220km and has a 44dB link loss. "The reason why there is a lot of talk about hybrid EDFA-Raman in the industry is that it works very well with coherent," says Rafik Ward, vice president of marketing at Finisar. Amplifier span distances of 80km are commonly used but the purpose of the demonstration was to showcase the product's capability, says Ward.
WSSes and multicast switches
NeoPhotonics has announced a modular multicast switch that allows an operator to grow a ROADM's node according to demand. The multicast switch is used to add colourless, directionless and contentionless (CDC) attributes to the ROADM. "You can have any wavelength [colourless] from any direction come out at any port [directionless]," says Lipscomb. "And if you have two identical wavelengths coming from different directions, you can drop them through the same switch [contentionless]."
Lipscomb cites as an example an 8-degree ROADM node, with each direction fibre carrying 100 dense WDM channels. Even if only a quarter of the channels are dropped, that is 200 channels, he says: "What we are announcing is a modular multicast switch; you can start with 4 channels and 4 drops and keep adding modular line cards as needed to add more drop ports and more directions."
NeoPhotonics modular multicast switches include such dimensions as 4x4, 4x16 and 8x16. "Carriers don't want to limit their future deployment but they also don't want to spend a lot of money now because they might want to drop 100 channels later," says Lipscomb.
JDSU announced its second-generation twin 1x20 wavelength-selective switch (WSS) that fits on a single-slot card. The twin WSS is used for advanced flexible-grid CDC-ROADM nodes.
The latest twin 1x20 WSS has the same functionality as JDSU's current twin 1x20 WSS that has been available for a year but which occupies two chassis slots. "It has the same capability but is considerably smaller," says Collings.
Indeed, the twin WSS is sufficiently compact that other functions can be added to the card such as amplification, optical power monitoring and optical service channels, communication channels between nodes used for such tasks as provisioning, power management and firmware updates.
For the OFC 2014 product round-up - Part 2, click here
