ECOC 2023 industry reflections - Final Part
Gazettabyte has been asking industry figures to reflect on the recent ECOC show in Glasgow. The final instalment emphasises coherent technology with contributions from Adtran, Cignal AI, Infinera, Ciena, and Acacia.
Jörg-Peter Elbers, head of advanced technology at Adtran
The ECOC 2023 conference and show was a great event. The exhibition floor was busy and offered ample networking opportunities. In turn, the conference and the Market Focus sessions provided information on the latest technologies, products, and developments.
One hot topic was coherent 800ZR modems. Several vendors demonstrated coherent 800ZR modules and related components. Importantly, these modules also boast new and improved 400 gigabit-per-second (Gbps) modes. The 120 gigabaud (GBd) symbol rate enables 400-gigabit dual-polarisation quadrature phase shift keying (DP-QPSK) transmission over demanding links and long-haul routes. In turn, the advent of 5nm CMOS digital signal processor (DSP) technology enables lower power DP-16QAM than 400ZR modules.
There is broad agreement that the next step in coherent transmission is a 240GBd symbol rate, paving the way to single-wavelength 1.6 terabit-per-second (Tbps) optical transport.
Meanwhile, the use of coherent optical technology closer to the network edge continues. Several players announced plans to follow Adtran and Coherent and jump on the low-power 100 gigabit-per-second ZR (100ZR) ‘coherent lite’ bandwagon. Whether passive optical networking (PON) systems will adopt coherent technology after 50G-PON sparked lively debate but no definitive conclusions.
The OIF 400ZR+ demonstration showed interoperability between a dozen optical module vendors over metro-regional distances. It also highlighted the crucial role of an intelligent optical line system such as Adtran’s FSP3000 OLS in automating operation and optimising transmission performance.
The post-deadline papers detailed fibre capacity records by combining multiple spectral bands and multiple fibre cores. The line-system discussions on the show floor focused on the practical implications of supporting C-, L-, extended, and combined band solutions for customers and markets.
From workshops to the regular sessions, the application of artificial intelligence (AI) was another prominent theme, with network automation a focus area. Examples show not only how discriminative AI can detect anomalies or analyse failures but also how generative AI can improve the interpretation of textual information and simplify human-machine and intent interfaces. For network engineers, ‘Copilot’-like AI assistance is close.
After ECOC is also before ECOC, so please mark in your calendars September 22-26, 2024. ECOC will celebrate its 50th anniversary next year and will take place in Frankfurt, Germany. As one of the General Chairs of the ECOC 2024 event, and on behalf of the entire organising committee, I look forward to welcoming you!
Andrew Schmitt, founder and directing analyst, Cignal AI
ECOC is a great show, it’s like OFC (the annual optical communications and networking event held in the US) but refined to only the critical elements. Here are my key takeaways.
The most impressive demonstration was 800ZR test boards and modules from Marvell and its partners Coherent and Lumentum. Within eight weeks of the first silicon, Marvell has demos up and running in-house and at its partners. The company has at least a 6-month lead in the 800ZR market, making intelligent tradeoffs to achieve this.
Lumentum showed an 8-QAM mode of operation that allows 800 gigabit transmission within a 100GHz channel spacing, which should be interesting. After the massive success of 400ZR, it’s natural to extrapolate the same success for 800ZR, but the use cases for this technology are substantially different. We also heard updates and broader support for 100ZR.
Linear drive pluggable optics (LPO) was a hot topic, although it was our impression that, while optimism ruled public discussion, scepticism was widely expressed in private. There was more agreement than disagreement with our recent report (see the Active Insight: The Linear Drive Market Opportunity). No one is more confident about LPO than the companies who view this as another opportunity to bid for business at hyperscale operators they don’t currently have.
The 200 gigabit per lane silicon/ physical media device (PMD)/ optics development continues, and it is on track to enable 1.6-terabit optics by 2024. Marvell had a more advanced and mature demo of what they showed behind closed doors at OFC. The advancements here are the real threat to adopting LPO, and people need to realise that LPO is competing with the power specs of 200 gigabits per lane, not 100 gigabits per lane solutions.
Also impressive was the comprehensive engineering effort by Eoptolink to show products that covered 100 gigabit and 200 gigabit per lane solutions, both retimed and linear. The company’s actions show that if you have the engineering resources and capital, rather than pick the winning technology, do everything and let the market decide. Also impressive is the CEO, who understood the demos and the seasoned application engineers. Kudos to keeping engaged with the products!
System vendors had a more significant presence at the show, particularly Ciena and Infinera. It’s unsurprising to see more system vendors since they are increasing investments in pluggables, particularly coherent pluggables.
We had many discussions about our forecasts for IPoDWDM deployment growth. This disruption is something that component vendors are excited about, and hardware OEMs view it as an opportunity to adjust how they deliver value to operators (see the Active Insight: Assessing the Impact of IP-over DWDM).
Lastly, the OIF coordinated 400ZR+ and OpenROADM interoperability testing despite the organisation not being directly involved in those industry agreements. The OIF is a fantastic organisation that gets valuable things done that its members need.
Paul Momtahan, director, solutions marketing, Infinera
ECOC 2023 provided an excellent opportunity to catch the latest trends regarding transponder innovation, coherent pluggables and optical line systems. A bonus was getting to the show without needing a passport.
Transponder innovation topics included coherent digital signal processor (DSP) evolution, novel modulators, and the maximum possible baud rate. DSP sessions included the possibility of offloading DSP functions into the photonic domain to reduce power consumption and latency.
There were also multiple presentations on constellation shaping, including enhanced nonlinear performance, reduced power consumption for probabilistic constellation shaping, and potential uses for geometric shaping.
Novel modulators with very high baud rates, including thin-film lithium niobate, barium titanate, plasmonic, and silicon-organic hybrid, were covered. The need for such modulators is the limited bandwidth potential of silicon photonics modulators, though each face challenges such as integration with silicon photonics and manufacturability.
From the baud rate session, the consensus was that 400GBd symbol rates are probable, up to 500GBd might be possible, but higher rates are unlikely. The critical challenges are the radio frequency (RF) interconnects and the digital-to-analogue and analogue-to-digital converters. However, several presenters wondered whether a multi-wavelength transponder might be more sensible for symbol rates above 200 to 250GBd.
Coherent pluggables were another topic, especially at 800 gigabit. However, one controversial topic was the longevity of coherent pluggables in routers (IPoDWDM). Several presenters argued the current period would pass once router port speeds and coherent port speeds no longer align.
As the coherent optical engines approach the Shannon limit, innovation is shifting towards optical line systems and fibres as alternative way to scale capacity.
Several presentations covered ROADM evolution to 64 degrees and even 128 degrees. A contrasting view is that ROADMs’ days are numbered to be replaced by fibre switches and full spectrum transponders, at least in core networks.
Additional options for scaling capacity included increasing the spectrum of existing bands with super-C and super-L. Lighting different bands, such as the S-band (in addition to C+L bands), is seen as the best candidate, with commercial solutions three to five years away.
Overall, it was a great event, and I look forward to seeing how things evolve by the time of next year’s ECOC show in Frankfurt. (For more, click here)
Helen Xenos, senior director, portfolio marketing, Ciena
This was my third year attending ECOC, and the show never disappoints. I always leave this event excited and energised about what we’ve accomplished as an industry.
Every year seems to bring new applications and considerations for coherent optical technology. This year, ECOC showcased the ever-growing multi-vendor ecosystem for 400-gigabit coherent pluggable transceivers, considerations in the evolution to 800-gigabit pluggables, evolution to coherent PON, quantum-secure coherent networking, and the evolution to 200 gigabaud and beyond. When will coherent technology make it into the data centre? A question still open for debate.
Ciena’s optical engineer wizards were on hand to share specifics about our recently announced 3nm CMOS-based WaveLogic 6 technology, which includes the industry’s first performance-optimised 1.6 teraburs-per-second (Tbps) optics as well as 800-gigabit pluggables.
It was exciting for me to introduce customers, suppliers and research graduates to their first view of 3nm chip performance results and show how these enable the next generation of products. And, of course, Ciena was thrilled that WaveLogic 6 was awarded the Most Innovative Coherent Module Product at the event.
Tom Williams, director of technical marketing at Acacia
From my perspective, while there weren’t as many major product announcements as OFC, several trends and technologies continued to progress, including OIF interoperability, 800ZR/ZR+, linear pluggable optics (LPO) and terabit optics.
The OIF interop demonstration was once again a highlight of the show. The booth was at the entrance to the exhibition and seemed to be packed with people each time I passed by.
OIF has expanded the scope of these demonstrations with each show, and this year was the largest ever. In addition to having the participation of 12 module vendors (with 34 modules), the focus was on the ZR+ operation. What was successfully demonstrated was a single-span 400ZR network and a multi-span network.
As co-chair of the OpenZR+ MSA, I was excited by the great collaboration with OIF. These efforts help to drive the industry forward. Karl Gass is not only the most creatively dressed person at every trade show; he is exceptional at coordinating these activities.
It is clear that linear drive pluggable optics (LPO) works in some situations, but views differ about how widespread its adoption will be and how standardisation should be addressed. I lived through the analogue coherent optics (ACO) experience. ACO was essentially a linear interface for a coherent module where the digital processing happened outside the module. For ACO, it was a DSP on the host board and for LPO it is the switch ASIC. The parameters that need to be specified are similar. There is a precedent for this kind of effort. Hopefully, lessons learned there will be helpful for those driving LPO. I am interested to see how this discussion progresses in the industry as some of the challenges are discussed, such as its current limited interoperability and support for 200 gigabits per lane.
There have been announcements from several companies about performance-optimised coherent optics in what we call Class 3 (symbol rates around 140 gigabaud), which support up to 1.2 terabits on a wavelength. Our CIM 8 module has been used in multiple field trials, demonstrating the performance benefits of these solutions.
Our CIM 8 (Coherent Interconnect Module 8) achieves this performance in a pluggable form factor. The CIM 8 uses the same 3D siliconisation technology we introduced for our 400-gigabit pluggables and enables operators to scale their network capacity in a cost- and power-efficient way.
ECOC '22 Reflections - Final Part
Gazettabyte has been asking industry and academic figures for their thoughts after attending ECOC 2022, held last month in Basel, Switzerland. In particular, what developments and trends they noted, what they learned, and what, if anything, surprised them.
In the final part, Dr. Sanjai Parthasarathi of Coherent, Acacia’s Tom Williams, ADVA’s Jörg-Peter Elbers and Fabio Pittalà of Keysight Technologies share their thoughts.
Dr. Sanjai Parthasarathi, Chief Marketing Officer, Coherent
The ECOC event represents an excellent opportunity for us – a vertically-integrated manufacturer selling at all levels of the value chain – to meet with customers, end-customers and partners/ suppliers.
There was a refreshing sense of optimism and excitement for optical communications, driven by relentless bandwidth growth, despite the macroeconomic backdrop.
The roadmap for optical transceivers is dictated by the electrical interface used for Ethernet switch chips. We have seen that play out yet again for 100-gigabit electrical lanes used for 25-terabit and 50-terabit Ethernet switches.
Several transceiver suppliers demonstrated products with 100 gigabit-per-lane electrical interfaces in quad and octal form factors. The optical lane of a transceiver typically begins at the same speed as the electrical lane and then progresses to a faster rate. This transition should be expected for 800-gigabit transceivers as well.
While 100 gigabit-per-lane transceivers, such as the 800G-DR8 and the 2x400G-FR4 devices, there were devices demonstrated that enable the transition to optical 200-gigabit lanes. It was satisfying to see a warm response for the demonstration of Coherent’s 200-gigabit electro-absorption modulated laser (EML) and Semtech’s 200-gigabit EML driver. I am confident that direct detection will play a predominant role in 800-gigabit and 1.6-terabit data centre links.
Despite the great interest in co-packaged optics, nearly all the working demonstrations at the show used pluggable transceiver modules. Industry colleagues are preparing for pluggable transceiver modules using the next 200-gigabit electrical interface. Indeed, at ECOC, there was an OIF-CEI 224G demo by Keysight and Synopsys.
One key topic at the show concerned whether ‘coherent lite’ or direct detect is the preferred solution for data centres and edge aggregation. The debate remains open and no one solution fits all. It will depend on the specific application and architecture. A broad portfolio supported by different technology platforms frees you to select the best approach to serve the customer’s needs.
I saw the industry responding to the need for disaggregation and innovative solutions for access and telecom. Coherent’s 100G ZR announcement is one such example, as well as the extra performance of high-power 400ZR+ coherent transceivers.
We started this trend and we now see others announcing similar solutions.
Arista’s demo, which featured 400ZR connections over a 120km data centre interconnect (DCI) link, enabled by our pluggable optical line system in a QSFP form factor, received much attention and interest.
Tom Williams, Senior Director of Marketing for Acacia, now part of Cisco.
Many of us are still of a mindset where any opportunity to get together and see industry friends and colleagues is a great show.
My focus is very much on the success of 400-gigabit pluggable coherent solutions.
We’ve been talking about these products for a long time, back to the initial OIF 400ZR project starting in late 2016. Since then, 400ZR/ZR+ has been a hot topic at every conference.
The commercial success of these solutions, and the impact that they’re having on network architectures, has been gratifying. These products have ramped in volumes not seen by any previous coherent technology.
The industry has done a great job at 400 gigabits, striking the right balance of power and performance. Now, we’re looking at 800 gigabits and working through some of the same questions. Discussions around 1.6 terabits have even started.
Much work is still required but what we heard from customers at ECOC is that the trend toward pluggable coherent will likely continue.
Jörg-Peter Elbers, Senior Vice President, Advanced Technology, Standards and IPR at ADVA
‘Never say never’ captures well ECOC’s content. There was no one groundbreaking idea but topics discussed in the past are back on the agenda, either because of a need or the technology has progressed.
Here are several of my ECOC takeaways:
- The 130 gigabaud (GBd) class of coherent optics is coming, and the generation after that – 240GBd – is on the horizon.
- Coherent optics continue to push towards the edge. Will there be a Very-High Speed Coherent PON after 50G High-Speed PON?
- Whether co-packaged optics or front-pluggable modules, electro-photonic integration is rapidly advancing with some interesting industry insights shared at the conference.
- Quantum-safe communication is becoming part of the regular conference program.
- Optical Satcom is gaining traction. Optical ground-to-space links are promising yet challenging.
Fabio Pittalà, Product Planner, Broadband and Photonics – Center of Excellence, Keysight Technologies
This was my first ECOC as an employee of Keysight. I spent most of my time at the exhibition introducing the new high-speed Keysight M8199B Arbitrary Waveform Generator.
There were a lot of discussions focusing on technologies enabling the next Ethernet rates. There is a debate about intensity-modulation direct detection (IMDD) versus coherent but also what modulation format, symbol rate or degree of parallelisation.
While the industry is figuring out the best solution, researchers achieved important milestones by transmitting the highest symbol rate and the highest net bitrate.
Nokia Bell-Labs demonstrated record-breaking transmission of 260-gigabaud dual-polarisation quadrature phase-shift keying (DP-QPSK) over 100km single-mode fibre.
Meanwhile, NTT broke the net bitrate record by transmitting more than 2 terabit-per-second using a probabilistic-constellation-shaped dual-polarisation quadrature amplitude modulation (DP-QAM) over different data centre links.
OFC highlights a burgeoning coherent pluggable market
A trend evident at the OFC show earlier this month was the growing variety of coherent pluggable modules on display.
Whereas a coherent module maker would offer a product based on a coherent digital signal processor (DSP) and a basic design and then add a few minor tweaks, now the variety of modules offered reflects the growing needs of the network operators.
Acacia, part of Cisco, announced two coherent pluggable to coincide with OFC. The Bright 400ZR+ QSFP-DD pluggable form factor is based on Acacia’s existing 400ZR+ offering. It has a higher transmit power of up to 5dBm and includes a tunable filter to improve the optical signal-to-noise ratio (OSNR) performance.
Acacia’s second coherent module is the fixed wavelength 400-gigabit 400G ER1 module designed for point-to-point applications.
“I can understand it being a little bit confusing,” says Tom Williams, vice president of marketing at Acacia. “We have maybe five or six configurations of modules based on the same underlying DSP and optical technology.”
Bright 400ZR+
The Bright 400ZR+ pluggable addresses a range of network architectures using the high-density QSFP-DD form factor, says Williams.
“Before you had to use the [larger] CFP2-DCO module, now we are bringing some of the functionality into the -DD,” he says. “The Bright 400ZR+ doesn’t replace the CFP2-DCO but it does move us closer to that.” As such, the module also supports OTN framing.
The Bright 400ZR+ has a higher launch power than the optical specification of the OpenZR+ standard but supports the same protocol so it can operate with OpenZR+ compliant pluggables.
The module uses internal optical amplification to achieve the 5dB launch power. The higher launch power is designed for various architectures and ROADM configurations.
“It is not that it allows a certain greater reach so much as the module can address a wider range of applications,” says Williams. “When you talk about colourless, directionless or colourless-directionless-contentionless (CDC-) reconfigurable optical add-drop multiplexing (ROADM) architectures, these are the types of applications this opens up.”
The integrated tunable filter tackles noise. In colourless ROADM-based networks, because the optical multiplexing occurs without filtering, the broadband out-of-band noise can raise the overall noise floor. This then decreases the overall OSNR. Amplification also increases the noise floor.
The tunable filter is used to knock down the overall noise floor, thereby improving the transmit OSNR.
The output power of the Bright 400ZR+ is configurable. The 5dBm launch power is used for ROADMs with array-waveguide gratings while for colourless multiplexing the tunable filter is used, reducing the output power to just above 1dBm.
“You are seeing an anchoring of interoperability that operators can use and then you are seeing people build on top of that with enhancements that add value and expand the use cases,” says Williams.
400 gigabits over 40km
As part of the OIF industry organisation’s work that defined the 400ZR specification, a 40km point-to-point unamplified link was also included. Acacia’s 400G ER1 is such an implementation with the ‘ER’ referring to extended reach, which IEEE defines as 40km.
“At every data rate there has always been an application for these ER reaches in access and enterprise,” says Williams. “The link is just a fibre, it’s like the 10km LR specification, but this goes over 40km.”
The ER1 has been designed to reduce cost and uses a fixed laser. ”We are not doing OSNR testing, it is based on a power-limited 40km link,” says Williams.
The OIF standard uses concatenated forward-error correction (CFEC) while Acacia employs its openFEC (oFEC) that enhances the reach somewhat.
Shipment updates
Acacia also reported a significant ramp in the shipment of its pluggables that use its Greylock coherent DSP.
It has shipped over 50,000 such pluggables, 20,000 alone shipped in Cisco’s last (second) fiscal quarter. “This is being driven by the expected early adopters of 400ZR, as well as a range of other applications,” says Williams.
Acacia says it has also shipped over 100,000 Pico DSP ports. Each AC1200 multi-haul module has two such ports.
The AC1200 sends up to 1.2 terabits over two wavelengths using Acacia’s 7nm CMOS Pico DSP. The multi-haul module is being used in over 100 networks while three of the four largest hyperscalers use the technology.
Acacia also demonstrated at OFC its latest multi-haul module announced last year, a 1.2 terabits single-wavelength design that uses its latest 5nm CMOS Jannu DSP and which operates at a symbol rate of up to 140 gigabaud.
Acacia says samples of its latest multi-haul module that uses its own Coherent Interconnect Module 8 (CIM 8) form factor will be available this year while general availability will be in 2023.
Post-deadline
Williams also presented a post-deadline paper at OFC.
The work outlined was the demonstration of the optical transmission of 400 Gigabit Ethernet flows over a 927km link. The trial comprised transmission through several networks and showed the interoperability of 400-gigabit QSFP-DD and CFP2 modules.
The work involved Orange Labs, Lumentum, Neophotonics, EXFO and Acacia.
Acacia's single-wavelength terabit coherent module
- Acacia has developed a 140-gigabaud, 1.2-terabit coherent module
- The module, using 16-ary quadrature amplitude modulation (16-QAM), can deliver an 800-gigabit wavelength over 90 per cent of the links of a North American operator.
Acacia Communications, now part of Cisco, has announced the first 1.2-terabit single-wavelength coherent pluggable transceiver.
And the first vendor, ZTE, has already showcased a prototype using Acacia’s single-carrier 1.2 terabit-per-second (Tbps) design.
The coherent module operates at a symbol rate of up to 140 gigabaud (GBd) using silicon photonics technology. Until now, indium phosphide has always been the material at the forefront of each symbol rate hike.
The module uses Acacia’s latest Jannu coherent digital signal processor (DSP), implemented in 5nm CMOS. The coherent transceiver also uses a custom form-factor pluggable dubbed the Coherent Interconnect Module 8 (CIM-8).
Trends
Acacia refers to its 1.2-terabit coherent pluggable as a multi-haul design, a break from its product categorisation as either embedded or pluggable.
“We are introducing a pluggable module that supports what has traditionally been the embedded market,” says Tom Williams, senior director of marketing at Acacia. “It supports high-capacity edge applications all the way out to long-haul and submarine.”
Pluggables are the fastest-growing segment of the coherent market. Whereas the mix of custom embedded designs to pluggable interoperable is 2:1, that is forecast to change with coherent pluggables accounting for two-thirds of the total ports.
Acacia highlights the growth of coherent pluggables with two examples.
Data centre operator Microsoft used Inphi’s (now Marvell’s) ColorZ direct-detect 100-gigabit modules for data centre interconnect for up to 80km whereas now the industry is moving to the 400ZR coherent MSA.
In turn, while proprietary embedded coherent solutions would be used for reconfigurable optical add-drop multiplexers (ROADMs), now, interoperable pluggable coherent modules are being adopted with the OpenROADM MSA.
“There is still a significant need in the market for full-performance multi-haul solutions but we think their development needs to be informed and influenced by pluggables,” says Williams.
1.2-terabit capacity
As coherent technology matures, the optical transmission performance is approaching the theoretical limit as defined by Claude Shannon.
“There is still opportunity for improvement,” says Williams. “We still have performance enhancements with each generation but it is becoming more incremental.”
Williams highlights how its latest design offers a 20–25 per cent spectral efficiency improvement compared to Acacia’s AC1200 that uses two wavelengths to deliver up to 1.2Tbps.
“As we increase baud rate, that alone does not give any improvement in spectral efficiency,” says Williams. It is the algorithmic enhancements that still boost performance.
Acacia is adopting an enhanced probabilistic constellation shaping (PCS) algorithm as well as an improved forward-error correction scheme. “There are also some benefits of a single carrier as opposed to using multiple carriers,” says Williams.
Design
The latest design is a natural extension of the AC1200 which can send 400 gigabits over ultra-long-haul distances, 800 gigabits using two wavelengths over most spans, and three 400-gigabit payloads over shorter, network-edge reaches. Now, this can all be done using a single wavelength.
A 150GHz channel is used when transmitting the module’s full rate of 1.2Tbps. And with the module’s adaptive baud rate feature, the rate can be reduced to fit a wavelength in a 75GHz-wide channel. Existing 800-gigabit transmissions use 112.5GHz channel widths and the multi-rate module also supports this spacing.
Williams says 16-QAM is the favoured signalling scheme used for transmission. This is what has been chosen for the 400ZR standard at 64GBd. Doubling the symbol rate means 800 gigabits can be sent using 16-QAM.
Acacia also highlights that future generation coherent designs, what it calls class 4 (see diagram above), will double the symbol rate again to some 240GBd. But the company is not saying whether the technology enabling such rates will be silicon photonics.
The company has long spoken of the benefits of using a silicon packaging approach for its coherent modules in terms of size, power and automated manufacturing. But as the symbol rate doubles, packaging plays a key role to help tackle challenging radio frequency (RF) design issues.
Acacia stacks the driver and trans-impedance amplifier (TIA) circuitry directly on top of its photonic integrated circuit (PIC) while its coherent DSP is also packaged as part of the design. “This gives us much better signal integrity than if we have the optics and DSP packaged separately,” says Williams.
The key to the design is getting the silicon photonics – the optical modulator, in particular – operating at 140GBd. “If you can, the packaging advantages of silicon are significant,” says Williams.
Acacia points out that with the migration of traffic from 100GbE to 400GbE it makes sense to offer a single-wavelength multi-rate design. And 400GbE will remain the mainstay traffic for a while. But once the transition to 800 gigabit occurs, the idea of supporting two coherent wavelengths – a future dual-wavelength “AC2400” – may make sense.
CIM-8
Acacia is using its own form factor and not a multi-source agreement (MSA) because the 1.2-terabit technology exceeds all existing client-side data rates.
In turn, the power consumption of the 1.2-terabit coherent module requires a custom form factor while launching an MSA based on the CIM-8 would have tipped off the competition, says Williams.
That said, Acacia has made no secret that its next high-end design following on from its 64GBd AC1200 would double the symbol rate and that the company would skip the 96GBd rate used by vendors such as Ciena, Huawei and Infinera already offering 800-gigabit wavelength systems.
For Acacia’s multi-rate design that needs to address submarine applications, the goal is to maximise transmission performance. In contrast, for a ZR+ coherent design that fits in a QSFP-DD, the limited power budget of the module constrains the design’s performance.
With 5nm Jannu DSP, Acacia realised it could not fit the design in the QSFP-DD or OSFP. But it could produce a pluggable multi-haul design with its CIM-8 that is slightly larger than the CFP2 form factor. And pluggables are advantageous when 4-8 can be fitted in a one-rack-unit (1RU) platform.
Acacia says its 140GBd module using 16-QAM will deliver an 800-gigabit wavelength over 90 per cent of the links of a North American operator. For the remaining, longest-distance links (the 10 per cent), it will revert to 400 gigabits.
In contrast, existing 800-gigabit systems operating at 96GBd cover up to 20 per cent of the links before having to revert to the slower speed, says Acacia.
Applications
Hyperscaler data centre operators are the main drivers for 1.2Tbps interconnects. The interface would typically be used in the metro to link smaller data centres to a larger aggregation data centre.
“The 1.2-terabit interface is just trying to maximise cost per bit; pushing more bits over the same set of optics,” says Williams.
The communications service providers’ requirements, meanwhile, are focussed on 400 gigabits and at some point will migrate to 800 gigabits, says Williams.
Several system vendors are expected to announce products using the new module in the coming months.
Acacia targets access networks with coherent QSFP-DD
- Acacia Communications has announced a 100-gigabit coherent QSFP-DD pluggable module.
- The module is the first of several for aggregation in the access network.
The second article addressing what next for coherent
Part 2: 100-gigabit coherent QSFP-DD
Acacia Communications has revisited 100-gigabit coherent but this time for access rather than metro networks.
Acacia’s metro 100-gigabit coherent pluggable product, a CFP, was launched in 2014. The pluggable has a reach from 80km to 1,200km and consumes 24-26W.
The latest coherent module is the first QSFP-DD to support a speed lower than the 400-gigabit 400ZR and ZR+ applications that have spurred the coherent pluggable market.
The launching of a 100-gigabit coherent QSFP-DD reflects a growing need to aggregate 10 Gigabit Ethernet (GbE) links at the network edge as 5G and fibre are deployed.
“The 10GbE links in all the different types of access networks highlight a need for a cost-effective way to do this aggregation,” says Tom Williams, vice president of marketing at Acacia.
Why coherent?
The deployment of 5G, business services, 10-gigabit passive optical networking (PON) and distributed access architecture (DAA) are driving greater traffic at the network edge.
Direct-detection optics is the main approach used for aggregation but Acacia argues coherent is now a contender.
Until now, Acacia has only been able to offer coherent metro products for access. The company believes a 100-gigabit coherent module is timely given the network edge traffic growth coupled with the QSFP-DD form factor being suited for the latest aggregation and switch platforms. Such platforms are not the high-capacity switches used in data centres yet port density still matters.
“We think we can trigger a tipping point and drive coherent adoption for these applications,” says Williams.
Using coherent brings robustness long associated with optical transport networks. “You just plug both ends in and it works,” he says.
In access, the quality of fibre in the network varies. With coherent, there is no need for an engineer to do detailed characterisations of the link thereby benefiting operational costs.
Adopting coherent technology for access also provides a way to scale. “You may only need 100 gigabits today but there is a clear path to 200 and 400 gigabit and the use of DWDM [dense wavelength-division multiplexing],” says Williams.
100-gigabit QDFP-DD
Acacia’s 100-gigabit QSFP-DD uses a temperature-controlled fixed laser and has a reach of 120km. The 120km span may rarely be needed in practice – up to 80km will meet most applications – but the extra margin will accommodate any vagaries in links.
The module uses Acacia’s 7nm CMOS low-power Greylock coherent digital signal processor (DSP). The Greylock is Acacia’s third-generation low power DSP chip that is used for its 400ZR and ZR+ modules.
The 100-gigabit QSFP-DD shares the same packaging as the 400ZR and ZR+ modules. The DSP, silicon-photonics photonic integrated circuit (PIC), modulator driver and trans-impedance amplifier (TIA) are all assembled into one package using chip-stacking techniques, what Acacia calls an opto-electronic multi-chip module (OEMCM).
“Everything other than the laser is in a single package,” says Williams. “The more we make optics look like electronics and the fewer interconnect points we have, the higher the reliability will be.”
The packaging approach brings size and optical performance benefits. The optics and DSP must be tightly coupled to ensure signal integrity as the symbol rates go up for 400-gigabit and soon 800-gigabit data rates. But this is less of an issue at 100-gigabit given the symbol rate is 32-gigabaud only.
Opportunities
The 100-gigabit QSFP-DD is now sampling and undergoing qualification. Acacia has yet to announce its general availability.
The company is planning other coherent modules for access including a tunable laser-based QSFP-DD as well as designs that meet various environmental requirements.
“We view coherent as moving into the access market and that will require solutions that address the entire market,” says Williams. That said, Acacia admits uncertainty remains as to how widely coherent will be adopted.
“The market has to play out and there are other competitive solutions,” says Williams. “We believe coherent will be the right solution but how that plays out near- to mid-term is uncertain.”
Acacia unveils its 400G coherent module portfolio
Acacia Communications has unveiled a full portfolio of 400-gigabit coherent optics and has provided test samples to customers, one being Arista Networks.
Delivering a complete set of modules offers a comprehensive approach to address the next phase of coherent optics, the company says.
The 400-gigabit coherent designs detailed by Acacia are implemented using the QSFP-DD, OSFP and CFP2 pluggable form factors.
Collectively, the pluggables support three performance categories: the 400ZR standard, OpenZR+ that is backed by several companies, and the coherent optics specification used for the Open ROADM multi-source agreement (MSA).
OIF-defined 400ZR standard designed for hyperscalers
“These are challenging specifications,” says Tom Williams, vice president of marketing at Acacia. “Even the 400ZR, where the objective has been to simplify the requirements.”
400ZR and OpenZR+
The OIF-defined 400ZR standard is designed for hyperscalers to enable the connection of switches or routers in data centres up to 120km apart.
The 400ZR standard takes in a 400 Gigabit Ethernet (GbE) client signal and outputs a 400-gigabit coherent signal for optical transmission.
“Hyperscaler customers want a limited subset of performance [with the ZR] because they don’t want to introduce operational complexity,” says Williams.
Acacia is implementing the 400ZR standard with two module offerings: the QSFP-DD and the OSFP.
Acacia is also a founding member of OpenZR+, the industry initiative that supports both 400ZR and extended optical performance modes. The other OpenZR+ members are NEL, Fujitsu Optical Components, Lumentum, Juniper Networks and Cisco Systems which is in the process of acquiring Acacia.
OpenZR+ supports 100GbE and its multiples (200GbE and 300GbE) input signals, not just 400GbE as used for ZR. To transmit the 200- 300- and 400GbE client signals, OpenZR+ uses quadrature phase-shift keying (QPSK), 8-ary quadrature amplitude modulation (8-QAM), and 16-QAM, respectively.
OpenZR+ also employs an enhanced forward-error correction (oFEC) used for the Open ROADM specification and delivers improved dispersion compensation performance.
“OpenZR+ is not just about going further but also being able to offer more functionality than 400ZR,” says Williams.
Acacia is implementing OpenZR+ using the QSFP-DD and OSFP form factors.
Open ROADM
The Open ROADM specification is the most demanding of the three modes and is targeted for use by the telecom operators. Here, a CFP2-DCO module is used due to its greater power envelope. And while the Open ROADM optics is aimed at telcos, the CFP2-DCO also supports OpenZR+ and 400ZR modes.
“The telcos are not as focussed on [face plate] density,” says Williams. “The CFP2-DCO has a higher output and is not limited to just Ethernet but also multiplexed client signals and OTN.”
Since line cards already use CFP2-DCO modules, the Open ROADM module enables a system upgrade. Existing line cards using the 200-gigabit CFP2-DCO may not support 400GbE client signals but with the Open ROADM CFP2’s higher symbol rate, it offers enhanced reach performance.
This is because the Open ROADM CFP2-DCO uses a 64 gigabaud (GBd) symbol rate enabling a 200-gigabit signal to be transmitted using QPSK modulation. In contrast, 32GBd is used for the existing 200-gigabit CFP2-DCOs requiring 16-QAM. Using QPSK rather than 16-QAM enables better signal recovery.
There is also an interoperability advantage to the new CFP2-DCO in that its 200-gigabit mode is compliant with the CableLabs specification.
All three designs – 400ZR, OpenZR+ and Open ROADM – use Acacia’s latest 7nm CMOS Greylock low-power coherent digital signal processor (DSP).
This is the company’s third-generation low-power DSP following on from its Sky and Meru DSPs. The Meru DSP is used in existing 32GBd 100/ 200-gigabit CFP2-DCOs.
3D stacking
Acacia has spent the last year and a half focusing on packaging, using techniques from the semiconductor industry to ensure the pluggable form factors can be made in volume.
The higher baud rate used for the 400-gigabit coherent modules means that the electronic ICs and the optics need to be closely coupled. “Moving up the baud rate means that the interconnection between the [modulator] driver [chip] and the modulator can become a limiting factor,” says Williams.
Acacia is not detailing the 3D design except to say that the Greylock DSP, its silicon-photonics photonic integrated circuit (PIC), and the modulator driver and trans-impedance amplifier (TIA) are all assembled into one package using chip-stacking techniques. The chip is then mounted onto a printed circuit board much like a BGA chip, resulting in a more scalable process, says Acacia.
“We have taken the DSP and optics and turned that into an electronic component,” says Williams. “Ultimately, we believe it will lead to improvements in reliability using this volume-repeatable process.”
Acacia says its modules will undergo qualification during most of this year after which production will ramp.
No one module design will be prioritised, says Williams: “There are a lot of benefits of doing all three, leveraging a lot of common elements.”
Books in 2019 - Final Part
Gazettabyte asks industry figures each year to cite the memorable books they have read. These include fiction, non-fiction and work-related titles.
In the second and final part, the recommendations during 2019 of Analysys Mason’s Dana Cooperson and Tom Williams from Acacia Communications are included.
Dana Cooperson, Research Director, Analysys Mason
I’ll cheat somewhat and go back several years when picking favourite books and then I’ll focus on titles read in 2019.
I’ve spent a lot of time over the past five years thinking about, helping my kids apply for, and paying for university education, so education-related books have been a focus.
My first recommendation is Excellent Sheep: The Miseducation of the American Elite and the Way to a Meaningful Life, by William Deresiewicz, an ex-professor and admissions counsellor at Yale.
I recommend it for its insight into the college admissions process, the business of US higher education, and how far some parents, prospective students, and colleges stray from what should be the goal: a good education. The recent “Varsity Blues” admissions scandal is a case in point.
The book, read after my first daughter’s run through the admissions obstacle course, validated my cynicism, but also left me and my younger daughter, who read it, empowered for our second attempt.
Three other education-related books offer different accounts of disadvantaged yet determined individuals who overcome challenging circumstances to become well-educated. And how friends and relatives can work to undermine those who strive for more. They also recount how difficult navigating the system can be for the disadvantaged and the crucial role of mentors.
Educated: A Memoir, by Tara Westover and Hillbilly Elegy: A Memoir of a Family and Culture in Crisis, by J. D. Vance, are well-known. These memoirs are insightful about the ‘anti-elite’, anti-education subcultures in the US (in Appalachia and survivalist Idaho, respectively).
Less well-known is A Hope in the Unseen: an American Odyssey from the Inner City to the Ivy League, by journalist Ron Suskind; by far my favourite of the three.
It traces the path of Cedric Jennings, a bright and determined African American boy from a poor, dangerous section of Washington, D.C., in the 1990s as he faces setback after setback in his quest for an education and a better life. It is a wonderfully written and deep book.
Other books gave me engrossing peeks into other eras, cultures, and species.
My 2019 reading started with Homegoing, by Yaa Gyasi, a story of two 18th century Ghanaian half-sisters, one of whom ends up enslaved in Mississippi. This epic novel spans eight generations of the sisters’ families and sheds light on the dark corners of the international slave trade and its legacy.
The central character of Eleanor Oliphant is Completely Fine, by Gail Honeyman, is smart, funny, and cringingly, endearingly quirky. The novel, set in present-day Scotland, has elements of a mystery as we slowly learn the roots of Eleanor’s trauma and just how twisted her psyche has become in her effort to outrun childhood tragedy.
I ended 2019 with A Gentleman in Moscow: A Novel, by Amor Towles. This novel’s plot spans Russian/ Soviet history from the Bolshevik revolution to the Cold War, and yet it unfolds almost entirely in a hotel.
Count Alexander Rostov, the titular protagonist, is an aristocrat whom the Bolsheviks deem a “former person” and sentenced to house arrest in Moscow’s Metropol Hotel. The Count, abetted by various friends and dogged by his chief antagonist, creates a life well-lived despite being a prisoner of the state. Here’s looking at you, Count!
Lastly, the book you didn’t know you needed to read about the species you didn’t know was so fascinating: The Soul of an Octopus: A Surprising Exploration into the Wonder of Consciousness, by journalist Sy Montgomery.
I’m never going to eat octopus again but that is a small price to pay for such an illuminating exposé on the physiology, lifecycle, and intelligence of the octopus; their personalities; and what we can learn about consciousness from a species alien to us.
Tom Williams, Vice President of marketing at Acacia Communications.
It may be a depressing story but the book that most impacted me in 2019 is entitled: What Made Maddy Run, by Kate Fagan.
It is a tragic story about a freshman, Madison Hollaran, at the University of Pennsylvania, who struggled with the pressures of freshman year as a scholarship athlete at an Ivy League school and committed suicide in her second semester.
Maddy seemed to have a perfect life as a star high-school athlete in soccer and track. She had a strong network of high-school friends and a supportive family, but she found herself lost at Penn and couldn’t find her way back to peace in her life.
Her family and close friends knew she was struggling but I don’t think anyone ever imagines events taking such a turn.
Maddy’s family provided the author with full access to her phone, computer and accounts. Stories from family and friends are interspersed with email and text discussions to provide a real sense of the pain she was struggling to communicate. Stitching these different strands together and the benefit of hindsight provide a fuller perspective.
As she approached her final act of desperation, several interactions presented themselves to offer her a different path out of the valley that she found herself in, but somehow she couldn’t recognise these opportunities. She had lost hope.
The book explores the pressures of freshman year, especially at an Ivy League school where students face a level of academic competitiveness never experienced before. Everyone there was at the top of their class in high-school.
In addition, athletes often feel the burden of living up to expectations to “earn” their scholarship. Their sport can become a responsibility or burden and no longer a source of enjoyment.
The book also explores how social media posts can disguise what someone like Maddie is feeling, making it even harder to recognise when a concerning situation has become a crisis.
As a parent of teenage daughters, I felt for her parents who knew she was struggling but didn’t know how to help. As parents, we want to fix our children’s problems, but as they approach adulthood, it is more difficult to have all the answers.
You know from the start how the book will end, but the chapter where she takes her life is as powerful as anything I’ve read. I can’t imagine how difficult it was for her family to provide the access to enable this book to be written, but I respect their strength and I hope it helps others in similar situations.
The book made a lasting impression on me.
Roy Rubenstein, Editor of Gazettabyte
I read some terrific titles in 2019 but none came close to the book What Dementia Teaches Us about Love, by Nicci Gerrard. (In the US, the title is The Last Ocean: A Journey Through Memory and Forgetting)
Gerrard is a journalist and novelist. She is also a co-founder of a campaign in the UK, named after her father, John, to allow carers to accompany dementia patients in hospitals. This follows her experience with her father who was left alone for days without visitors due to a virus outbreak.
Gerrard describes how, “… away from the home he loved, stripped of familiar routines and surrounded by strangers and machines, he swiftly lost his bearings and his fragile hold on himself. There is a great chasm between care and ‘care’, and my father fell into it.”
The book explores the disease – the gradual fragmentation of a person as they lose memory, language, recognition of their surroundings and, inevitability, their health.
But the book is more than that: it is a treatise on what it is to be human. What makes you, you? The grounding of memory and what it means to start forgetting. What is home? And the conflicting demands of caring: preserving the self while being endlessly drawn to caring for a loved one that is slowly losing and being lost.
The book is part memoir and part study. It is also sprinkled with moving human-interest stories. It may be hard to read at times but the book is uplifting.
Gerrard has written an original work on a topic that is not short of literature. Her writing also causes you to pause and reflect on what you’ve read.
For example, she starts the book with a story of how her father, after a decade of dementia, joins the family on a holiday in Sweden and visits a lake.
“My father, old and frail, swam out a few yards and then he started to sing. It is a song I’d never heard before, and never heard since …
“His self – bashed about by the years, picked apart by his dementia – was, in this moment of kindness, beyond language, consciousness and fear, lost and contained in the multiplicity of things and at home in the vast wonder of life.”
Acacia heralds the era of terabit-plus optical channels
Acacia Communications has unveiled the AC1200-SC2 that delivers 1.2 terabits over a single optical channel.
The SC2 (single chip, single channel) is an upgrade of Acacia’s high-end AC1200 module. The AC1200 too is a 1.2-terabit module but uses two optical channels, each transmitting a 600-gigabit wavelength. The SC2 sends 1.2 terabits using two sub-carriers that fit within a single 150GHz-wide channel.
Each line is a data rate. Shown is the scope of how the baud rate and the modulation scheme can be varied and its impact on channel width, reach and data rate. Source: ADVA.
“In the SC2, we take care of everything so the user configures a single channel that is easier to manage in their network,” says Tom Williams, vice president of marketing at Acacia.
1.2-terabit channel
Acacia unveiled the AC1200 at the ECOC show in 2017. With its introduction, Acacia gained an advantage over its system-vendor rivals in bringing a 1.2-terabit coherent module to market using 600-gigabit wavelengths. The module supports up to 64-ary quadrature amplitude modulation (64-QAM) and a symbol rate of 69 gigabaud (GBd).
Systems vendors such as Ciena, with its WaveLogic 5, and Infinera, with its Infinite Coherent Engine 6 (ICE6), responded with their next-generation coherent designs that use symbol rates approaching 100GBd and support an 800-gigabit wavelength.
Sell-side research analysts interpreted the coherent developments as Acacia having a window of opportunity to exploit the AC1200 until the systems vendors’ coherent designs come to market in the coming year. The analysts also noted how 400 Gigabit Ethernet client signals better fit in an 800-gigabit wavelength compared to a 600-gigabit wavelength.
Then, in July, Acacia’s status as a merchant coherent technology supplier changed with the announcement that Cisco Systems is to acquire the company for $2.6 billion. Now, Acacia has detailed the SC2 as its acquisition awaits completion.
AC1200-SC2
The SC2 uses the same form factor and electrical connector as the AC1200 module, simplifying the upgrading of system designs using the AC1200. However, the SC2 module uses a single fibre pair for its optical output whereas the AC1200 uses two pairs, one for each channel.
The SC2 module shares the same Pico coherent digital signal processor (DSP) and baud rates as the AC1200. The Pico DSP uses fractional quadrature amplitude modulation (QAM) and an adjustable baud rate.
Fractional QAM allows the tuning of the transmitted data rate by using a mix of adjacent modulation formats. For example, 8-QAM and 16-QAM are alternated, and the percentage of time each is used determining the resulting data rate. In turn, the baud rate can be increased to widen the signal’s spectrum, if the optical channel permits, such that using a lower modulation scheme may become possible, improving the reach (see diagram above).
The AC1200 uses 50GHz- and 75GHz-wide channels while the SC2 uses 50-150GHz channels. For 600-gigabit and 1.2-terabit transmissions, the widest channels are used: 75GHz for the AC1200, and 150GHz for the SC2. “But as you go down in data rate, you can address the transmission in multiple ways,” says Williams. “You can run a higher modulation scheme in a narrow channel or, with a wider channel, run a lower modulation scheme to go further.”
The result optical performance means that the SC2 can be used for multiple applications: from short-span data centre interconnect where the full 1.2-terabit capacity is sent using 64-QAM, to metro-regional and long-haul distances using 800-gigabit and 16-QAM, all the way to ultra-long-haul terrestrial and subsea links with 400-gigabitand quadrature phase-shift keying (QPSK) modulation.
The AC1200 and the SC2 have comparable optical performance in terms of spectral efficiency and reach. This is unsurprising given how both modules use the same Pico DSP, baud rates and modulation schemes.
The AC1200 uses two 75GHz channels, each carrying 600 gigabits, to send 1.2 terabits, while the SC2 uses two sub-carriers in a 150GHz channel. However, the SC2 has a slight advantage since no guard band is needed between the two channels as is required with the AC1200 (unless the AC1200 is sending a two-channel ‘superchannel’ whereby no dead zone is needed between the channels).
Acacia is not detailing how it generates the optical sub-carriers besides saying the change stems from the interface between the Pico DSP and its silicon photonics-based photonic integrated circuit (PIC). The company will also not say if the SC2 uses a new PIC design.
Operational benefits
The fact that the SC2 and AC1200 deliver the same reach and capacity may explain why Acacia downplays the argument that the company has again leapfrogged its rivals with the advent of a module that sends 1.2 terabits over a single channel.
Instead, Acacia stresses the system and operational benefits resulting from doubling the data transmitted per channel.
“The SC2 module allows the entire capacity to be managed as a single channel,” says Williams. “The original [AC1200] module is well-suited to brownfield networks operating with 50GHz or 75GHz spacing, while the SC2 offers advantages in greenfield network architectures that can use channel plans up to 150GHz.”
Using a higher-capacity channel requires fewer optical components and reconfigurable optical add/ drop multiplexer (ROADM) ports thereby reducing networking costs, says Williams.
Using 150GHz-wide channels also aligns with an emerging consensus among network operators regarding wavelength roadmaps. “Network operators want to operate on some standardised grid based on regular multiples [50GHz, 75GHz] because it avoids fragmentation,” says Williams.
Availability
Acacia is already providing the SC2 module to certain customers that are undertaking validation testing. The firm is ready to ramp production based on particular customer demand.
Acacia will also be demonstrating its latest module at this week’s ECOC show being held in Dublin.
Acacia eyes pluggables as it demos its AC1200 module
The emerging market opportunity for pluggable coherent modules is causing companies to change their strategies.
Ciena is developing and plans to sell its own coherent modules. And now Acacia Communications, the coherent technology specialist, says it is considering changing its near-term coherent digital signal processor (DSP) roadmap to focus on coherent pluggables for data centre interconnect and metro applications.
Source: Gazettabyte
DSP roadmap
Acacia’s coherent DSP roadmap in recent years has alternated between an ASIC for low-power, shorter-reach applications followed by a DSP to address more demanding, long-haul applications.
In 2014, Acacia announced its Sky 100-gigabit DSP for metro applications that was followed in 2015 by its Denali dual-core DSP that powers its 400-gigabit AC-400 5x7-inch module. Then, in 2016, Acacia unveiled its low-power Meru, used within its pluggable CFP2-DCO modules. The high-end 1.2-terabit dual-core Pico DSP used for Acacia’s board-mounted AC1200 coherent module was unveiled in 2017.
“The 400ZR is our next focus,” says Tom Williams, senior director of marketing at Acacia.
The 400ZR standard, promoted by the large internet content providers, is being developed to link switches in separate data centres up to 80km apart. Acacia’s subsequent coherent DSP that follows the 400ZR may also target pluggable applications such as 400-gigabit CFP2-DCO modules that will span metro and metro-regional distances.
“There is a trend to pluggable, not just the 400ZR but the CFP2-DCO [400-gigabit] for metro,” says Williams. “We are still evaluating whether that causes a shift in our overall cadence and DSP development.”
AC1200 trials
Meanwhile, Acacia has announced the results of two transatlantic trials involving its AC1200 module whose production is now ramping.
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“There is a trend to pluggable, not just the 400ZR but the CFP2-DCO [400-gigabit] for metro”
In the first trial, Acacia, working with ADVA, transmitted a 300-gigabit signal over a 6,800km submarine cable. The 300-gigabit wavelength occupied a 70GHz channel and used ADVA’s Teraflex technology, part of ADVA’s FSP 3000 CloudConnect platform. Teraflex is a one-rack-unit (1RU) stackable chassis that supports three hot-pluggable 1.2-terabit sleds, each sled incorporating an Acacia AC1200 module.
In a separate trial, the AC1200 was used to send a 400-gigabit signal over 6,600km using the Marea submarine cable. Marea is a joint project between Microsoft, Facebook and Telxius that links the US and Spain. The cable is designed for performance and uses an open line system, says Williams: “It is not tailored to a particular company’s [transport] solution”.
The AC1200 module - 40 percent smaller than the 5x7-inch AC400 module - uses Acacia’s patented Fractional QAM (quadrature amplitude modulation) technology. The technology uses probabilistic constellation shaping that allows for non-integer constellations. “Instead of 3 or 4 bits-per-symbol, you can have 3.56 bits-per-symbol,” says Williams.
Acacia’s Fractional QAM also uses an adaptive baud rate. For the trial, the 400-gigabit wavelength was sent using the maximum baud rate of just under 70 gigabaud. Using the baud rate to the full allows a lower constellation to be used for the 400-gigabit wavelength thereby achieving the best optical signal-to-noise ratio (OSNR) and hence reach.
In a second demonstration using the Marea cable, Acacia demonstrated a smaller-width channel in order to maximise the overall capacity sent down the fibre. Here, a lower baud rate/ higher constellation combination was used to achieve a spectral efficiency of 6.41 bits-per-second-per-Hertz (b/s/Hz). “If you built out all the channels [on the fibre], you achieve of the order of 27 terabits,” says Williams.
Pluggable coherent
The 400ZR will be implemented using the same OSFP and QSFP-DD pluggable modules used for 400-gigabit client-side interfaces. This is why an advanced 7nm CMOS process is needed to implement the 400ZR DSP so that its power consumption will be sufficiently low to meet the modules’ power envelopes when integrated with Acacia’s silicon-photonics optics.
There is also industry talk of a ZR+, a pluggable module with a reach exceeding80km. “At ECOC, there was more talk about the ZR+,” says Williams. “We will see if it becomes standardised or just additional proprietary performance.”
Another development is the 400-gigabit CFP2-DCO. At present, the CFP2-DCO delivers up to 200-gigabitwavelengths but the standard, as defined by the Optical Internetworking Forum (OIF), also supports 400 gigabits.
Williams says that there a greater urgency to develop the 400ZR than the 400-gigabit CFP2-DCO. “People would like to ramp the ZR pretty close to the timing of the 400-gigabit client-side interfaces,” says Williams. And that is likely to be from mid-2019.
In contrast, the 400-gigabit CFP2-DCO pluggable while wanted by carriers for metro applications, is not locked to any other infrastructure build-out, says Williams.
Oclaro uses Acacia’s Meru DSP for its CFP2-DCO
Oclaro will use Acacia Communications’ coherent DSP for its pluggable CFP2 Digital Coherent Optics (CFP2-DCO) module. The module will be compatible with Acacia’s own CFP2-DCO, effectively offering customers a second source.
Tom Williams This is the first time Acacia is making its coherent DSP technology available to a fellow module maker, says Tom Williams, Acacia’s senior director, marketing.
Acacia benefits from the deal by expanding the market for its technology, while Oclaro gains access to a leading low-power coherent DSP, the Meru, and can bring to market its own CFP2-DCO product.
Williams says the move was encouraged by customers and that having a second source and achieving interoperability will drive CFP2-DCO market adoption. That said, Acacia is not looking for further module partners. “With two strong suppliers, we don’t see a need to add additional ones,” says Williams.
“This agreement is a sign that the market is reaching maturity, with suppliers transitioning from grabbing market share at all costs to more rational strategies,” says Vladimir Kozlov, CEO and founder of LightCounting Market Research.
CFP2-DCO
The CFP2-DCO is a dense wavelength-division multiplexing module that supports 100-gigabit and 200-gigabit data rates.
With the CFP2-DCO design, the coherent DSP sits within the module, unlike the CFP2 Analog Coherent Optics (CFP2-ACO) where the DSP chip is external, residing on the line card.
According to Kevin Affolter, Oclaro’s vice president strategic marketing, the company looked at several merchant and non-merchant coherent DSPs but chose the Meru due to its low power consumption and its support for 200 gigabits using 8-ary quadrature amplitude modulation (8-QAM) as well as the 16-QAM scheme. Using 8-QAM extends the optical reach of 200-gigabit wavelengths.
This agreement is a sign that the market is reaching maturity, with suppliers transitioning from grabbing market share at all costs to more rational strategies
At 100 gigabits the CFP2-DCO achieves long-haul distances of 2,000km whereas at 200 gigabit at 8-QAM, the reach is in excess of 1,000km. The 8-QAM requires a wider passband than the 16-QAM, however, such that in certain metro networks where the signal passes through several ROADM stages, it is better to use the 16-QAM mode, says Acacia.
Source: Acacia, Gazettabyte
Oclaro’s design will combine the Meru with its indium phosphide-based optics whereas Acacia’s CFP2-DCO uses silicon photonics technology. The power consumption of the CFP2-DCO module is of the order of 20W.
The two companies say their CFP2-DCO modules will be compatible with the multi-source agreement for open reconfigurable add-drop multiplexers (ROADMs). The Open ROADM MSA is backed by 16 companies, eight of which are operators. The standard currently only defines 100-gigabit transmission based on a hard-decision forward-error correction.
“There are several carriers, AT&T being the most prominent, within Open ROADM,” says Affolter. “It makes sense for both companies to make sure the needs of Open ROADM are addressed.”
Coherent shift
In 2017, Oclaro was one of three optical module companies that signed an agreement with Ciena to use the systems vendor’s WaveLogic Ai coherent DSP to develop a 400-gigabit transponder.
Kevin Affolter
Affolter says the Ciena and Acacia agreements should be seen as distinct; the 400-gigabit design is a large, 5x7-inch non-pluggable module designed for maximum reach and capacity. “The deals are complementary and this announcement has no impact on the Ciena announcement,” says Affolter.
Does the offering of proprietary DSPs to module makers suggest a shift in coherent that has always been seen as a strategic technology that allows for differentiation?
Affolter thinks not. “There are several vertically integrated vendors with their own DSPs that will continue to leverage their investment as much as they can,” he says. “But there is also an evolution of end customers and network equipment manufacturers that are moving to more pluggable solutions and that is where the -DCO really plays.”
Oclaro expects to have first samples of its CFP2-DCO by year-end. Meanwhile, Acacia’s CFP2-DCO has been generally available for over six months.