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.
Ciena advances coherent technology on multiple fronts
- Ciena has unveiled the industry’s first coherent digital signal processor (DSP) to support 1.6-terabit wavelengths
- Ciena announced two WaveLogic 6 coherent DSPs: Extreme and Nano
- WaveLogic 6 Extreme operates at a symbol rate of up to 200 gigabaud (GBd) while the Nano, aimed at coherent pluggables, has a baud rate from 118-140GBd
Part 1: WaveLogic 6 coherent DSPs
Ciena has leapfrogged the competition by announcing the industry’s first coherent DSP operating at up to 200GBd.
The WaveLogic 6 chips are the first announced coherent DSPs implemented using a 3nm CMOS process.
Ciena’s competitors are – or will soon be – shipping 5nm CMOS coherent DSPs. In contrast, Ciena has chosen to skip 5nm and will ship WaveLogic 6 Extreme coherent modems in the first half of 2024.
Using a leading CMOS process enables the cramming of more digital logic and features in silicon. The DSP also operates a faster analogue front-end, i.e. analogue-to-digital converters (ADC) and digital-to-analogue (DAC) converters.
The WaveLogic 6 matches Ciena’s existing WaveLogic 5 family in having two DSPs: Extreme, for the most demanding optical transmission applications, and Nano for pluggable modules.
WaveLogic 6 Extreme is the first announced DSP that supports a 1.6-terabit wavelength; Acacia’s (Cisco) coherent DSP supports 1.2-terabit wavelengths and other 1.2-terabit wavelength DSPs are emerging.
WaveLogic 6 Nano addresses metro-regional networks and data centre interconnect (up to 120km). Here, cost, size, and power consumption are critical. Ciena will offer the WaveLogic 6 in QSFP-DD and OSFP pluggable form factors.
Class 3.5
Network traffic continues to grow exponentially. Ciena notes that the total capacity of its systems shipped between 2010 and 2021 has grown 150x, measured in petabits per second.
Increasing the symbol rate is the coherent engineers’ preferred approach to reduce the cost per bit of optical transport.
Doubling the baud rate doubles the data sent using the same modulation scheme. Alternatively, the data payload can be sent over longer spans.
However, upping the symbol rates increases the optical wavelength’s channel width. Advanced signal processing is needed to achieve further spectral efficiency gains.
One classification scheme of coherent modem symbol rate defines first-generation coherent systems operating at 30-34GBd as Class 1. Class 2 modems double the rate to 60-68GBd. The OIF’s 400ZR standard operating at 64GBd is a Class 2 coherent modem.
Currently-deployed optical transport systems operating at 90-107GBd reside between Class 2 and Class 3 (120-136GBd). Ciena’s WaveLogic 5 Extreme is one example, with its symbol rate ranging from 95-107GBd. Ciena has shipped over 60,000 WaveLogic 5 Extreme DSPs to over 200 customers.
Acacia’s latest CIM-8 coherent modem, now shipping, operates at 140GBd, making it a Class 3 design. Infinera, NEL, and Nokia announced their Class 3 devices before the OFC 2023 conference and exhibition.
Now Ciena, with its 200GBd WaveLogic 6 Extreme, sits alone between Class 3 and Class 4 (240-272GBd).
WaveLogic 6 Extreme
Ciena has extended the performance of all the components of the Extreme-based coherent modem to work at 200GBd.
These components include the DSP’s analogue front-end: the ADCs and DACs, the coherent optics and the modulator drivers and TIAs. All must operate with a 100GHz bandwidth.
To operate at 200GBd, the ADCs and DACs must sample over 200 giga-samples a second. This is pushing ADC and DAC design to the limit.
The coherent modem’s optics and associated electronics must also have a 100GHz operating bandwidth. Ciena developed the optics in-house and is also working with partners to bring the coherent optics to market with a 100GHz bandwidth.
Ciena uses silicon photonics for the Extreme’s integrated coherent receiver (ICR) optics. For the coherent driver modulator (CDM) transmitter, Ciena is using indium phosphide and is also evaluating other technology such as thin-film lithium niobate.
“There are multiple options that are available and being looked at,” says Helen Xenos, senior director of portfolio marketing at Ciena.
Much innovation has been required to achieve the fidelity with 100GHz electro-optics and get the signalling right between the transmitter-receiver and the ASIC, says Xenos.
Ciena introduced frequency division multiplexing (FDM) sub-carriers with the WaveLogic 5 Extreme, a technique to help tackle dispersion. With the introduction of edgeless clock recovery, Ciena has created a near-ideal rectangular spectrum with sharp edges.
“First, inside this signal, there are FDM sub-carriers, but you don’t see them because they are right next to each other,” says Xenos. “Getting rid of this dead space between carriers enables more throughput.”
Making the signal’s edges sharper means that wavelengths are packed more tightly, better using precious fibre spectrum. Edgeless clock recovery alone improves spectral efficiency by between 10-13 per cent, says Xenos.
Moving to 3nm allows additional signal processing. As an example, Ciena’s WaveLogic 6 Extreme DSP can select between 1, 2, 4 and 8 sub-carriers based on the dispersion on the link. WaveLogic 5 Extreme supports 4 sub-carrier FDM only.
The baud rate is also adjustable from 67-200GBd, while for the line rate, the WaveLogic 6 supports 200-gigabit to 1.6-terabit wavelengths using probabilistic constellation shaping (PCS).
Another signal processing technique used is multi-dimensional constellation shaping. These are specific modulations that are added to support legacy submarine links.
“For compensated submarine cables that have specific characteristics, they need a specialised type of design also in the DSP,” says Xenos.
Ciena also uses nonlinear compensation techniques to squeeze further performance and allow higher power signals, improving overall link performance.
Ciena can address terrestrial and new and legacy submarine links with the WaveLogic 6 Extreme running these techniques.
Xenos cites performance examples using the enhanced DSP performance of the WaveLogic 6 Extreme.
Using WaveLogic 5, an 800-gigabit wavelength can be sent at 95GBd using a 112.5GHz-wide channel. The 800-gigabit signal can cross several reconfigurable optical add-drop multiplexer (ROADM) hops.
Sending a 1.6-terabit wavelength at 185GBd over a similar link, the signal occupies a 200GHz channel. “And you get better performance because of the extra DSP enhancements,” says Xenos.
The operator Southern Cross has simulated using the WaveLogic 6 Extreme on its network and says the DSP will be able to send one terabit of data over 12,000km.
Optical transport systems benefits
Systems benefits of the Extreme DSP include doubling capacity, transmitting a 1.6-gigabit wavelength, and halving the power consumed per bit.
The WaveLogic 6 Extreme will fit within existing Ciena optical transport kit.
Xenos said the design goal is to get to the next level of cost and power reduction and maximise the network coverage for 800-gigabit wavelengths. This is why Ciena chose to jump to 3nm CMOS for the WaveLogic 6 Extreme, skipping 5nm CMOS.
WaveLogic 6 Nano
The 3nm CMOS WaveLogic 6 Nano addresses pluggable applications for metro and data centre interconnect.
“The opportunity is still largely in front of us [for coherent pluggables],” says Xenos.
The current WaveLogic 5 Nano operating between 31.5-70GBd addresses 100-gigabit to 400-gigabit coherent pluggable applications. These include fixed grid networks using 50GHz channels and interoperable modes such as OpenROADM, 400ZR and 400ZR+. Also supported is the 200-gigabit CableLabs specification.
The WaveLogic 5 Nano is also used in the QSFP-DD module with embedded amplification for high-performance applications.
There is also a new generation of specifications being worked on by standards bodies on client side and line side 800-gigabit and 1.6-terabit interfaces.
Developments mentioned by Xenos include an interoperable probabilistic constellation shaping proposal to be implemented using coherent pluggables.
The advent of 12.8-terabit and 25.6-terabit Ethernet switches gave rise to 400ZR. Now with the start of 51.2-terabit and soon 102.4-terabit switches, the OIF’s 800ZR standard will be needed.
There is also a ‘Beyond 400 Gig’ ITU-T and OpenROADM initiative to combine the interoperable OpenZR+ and the 400-gigabit coherent work of the OpenROADM MSA for a packet-optimised 800-gigabit specification for metro applications.
Another mode is designed to support not just Ethernet but OTN clients.
Lastly, there will also be long-distance modes needed at 400, 600, and 800-gigabit rates.
“With WaveLogic 6 Nano, the intent is to double the capacity within the same footprint,” says Xenos.
In addition to these initiatives, the WaveLogic 6 Nano will address a new application class for much shorter spans – 10km and 20km – at the network edge. The aim is to connect equipment across buildings in a data centre campus, for example.
Some customers want a single channel design and straightforward forward-error correction. Other customers with access to limited capacity will want a wavelength division multiplexed (WDM) solution.
The Nano’s processing and associated optics will be tuned to each application class. “The engineering is done so that we only use the performance and power required for a specific application,” says Xenos.
A Nano-based coherent pluggable connecting campus buildings will differ significantly from a pluggable sending 800 gigabits over 1,000km or across a metro network with multiple ROADM stages, she says.
The WaveLogic 6 Nano will be used with silicon photonics-based coherent optics, but other materials for the coherent driver modulator transmitter may be used.
Availability
Ciena taped out the first 3nm CMOS Extreme and Nano ICs last year.
The WaveLogic 6 Extreme-based coherent modem will be available for trials later this year. Product shipments and network deployments will begin in the first half of 2024.
Meanwhile, shipments of WaveLogic 6 Nano will follow in the second half of 2024.
ECOC '22 Reflections - Part 2
Gazettabyte is asking industry and academic figures for their thoughts after attending ECOC 2022, held in Basel, Switzerland. In particular, what developments and trends they noted, what they learned, and what, if anything, surprised them.
In Part 2, Broadcom‘s Rajiv Pancholy, optical communications advisor, Chris Cole, LightCouting’s Vladimir Kozlov, Ciena’s Helen Xenos, and Synopsys’ Twan Korthorst share their thoughts.
Rajiv Pancholy, Director of Hyperscale Strategy and Products Optical Systems Division, Broadcom*
The buzz at the show reminded me of 2017 when we were in Gothenburg pre-pandemic, and that felt nice.
Back then, COBO (Consortium for On-Board Optics) was in full swing, the CWDM8 multi-source agreement (MSA) was just announced, and 400-gigabit optical module developments were the priority.
This year, I was pleased to see the show focused on lower power and see co-packaged optics filter into all things ECOC.
Broadcom has been working on integrating a trans-impedance amplifier (TIA) into our CMOS digital signal processor (DSP), and the 400-gigabit module demonstration on the show floor confirmed the power savings integration can offer.
Integration impacts power and cost but it does not stop there. It’s also about what comes after 2nm [CMOS], what happens when you run out of beach-front area, and what happens when the maximum power in your rack is not enough to get all of its bandwidth out.
It is the idea of fewer things and more efficient things that draws everyone to co-packaged optics.
The OIF booth showcased some of the excitement behind this technology that is no longer a proof-of-concept.
Moving away from networking and quoting some of the ideas presented this year at the AI Hardware Summit by Alexis Bjorlin, our industry needs to understand how we will use AI, how we will develop AI, and how we will enable AI.
These were in the deeper levels of discussions at ECOC, where we as an industry need to continue to innovate, disagree, and collaborate.
Chris Cole, Optical Communications Advisor
I don’t have many substantive comments because my ECOC was filled with presentations and meetings, and I missed most of the technical talks and market focus presentations.
It was great to see a full ECOC conference. This is a good sign for OFC.
Here is an observation of what I didn’t see. There were no great new silicon photonics products, despite continued talk about how great it is and the many impressive research and development results.
Silicon photonics remains a technology of the future. Meanwhile, other material systems continue to dominate in their use in products.
Vladimir Kozlov, CEO of LightCounting
I am surprised by the progress made by thin-film lithium niobate technology. There are five suppliers of these devices now: AFR, Fujitsu, Hyperlight, Liobate, and Ori-chip.
Many vendors also showed transceivers with thin-film lithium niobate modulators inside.
Helen Xenos, senior director of portfolio marketing at Ciena
One key area to watch right now is what technology will win for the next Ethernet rates inside the data centre: intensity-modulation direct detection (IMDD) or coherent.
There is a lot of debate and discussion happening, and several sessions were devoted to this topic during the ECOC Market Focus.
Twan Korthorst, Group Director Photonic Solutions at Synopsys.
My main observations are from the exhibition floor; I didn’t attend the technical conference.
ECOC was well attended, better than previous shows in Dublin and Valencia and, of course, much better than Bordeaux (the first in-person ECOC in the Covid era).
I spent three days talking with partners, customers and potential customers, and I am pleased about that.
I didn’t see the same vibe around co-packaged optics as at OFC; not a lot of new things there.
There is a feeling of what will happen with the semiconductor/ datacom industry. Will we get a downturn? How will it look? In other words, I noticed some concerns.
On the other hand, foundries are excited about the prospects for photonic ICs and continue to invest and set ambitious goals.
Ciena's multi-format 400G coherent QSFP-DD pluggable
Ciena showcased a working 400-gigabit Universal coherent pluggable module at the ECOC 2022 conference and exhibition in Basel, Switzerland.
Ciena is using its WaveLogic 5 Nano coherent digital signal processor (DSP) for the Universal QSFP-DD coherent pluggable module.
“We call it universal because it supports many transmission modes – interoperable and high performance; the most in the industry,” says Helen Xenos, senior director of portfolio marketing at Ciena.
The pluggable has custom extended-performance modes and supports three industry formats: the 400ZR interoperable standard, the 400ZR+ multi-source agreement (MSA), and the OpenROADM MSA. (See tables below).
IP over DWDM
Communications service providers (CSPs) want to add pluggable coherent modules to their IP routers, removing the need for a separate transponder card or box linking the router to the optical line system.
The advent of coherent QSFP-DD pluggables has meant the same form factor can be used for client-side and line-side optics, ensuring efficient use of the router ports.
The CSPs want the coherent QSFP-DD module to have sufficient optical performance to meet their demanding networking requirements. For example, the module’s output signal can pass through the filtering stages of reconfigurable optical add-drop multiplexers (ROADMs) along the optical link.
Optical amplification and filtering
Ciena’s coherent QSFP-DD adds a fibre-based optical amplifier and a tunable optical filter to the coherent photonics and electronic ICs.
The optical amplification enables the high-performance mode and the launching of a 4dBm output signal. In contrast, 400ZR and 400ZR+ have a launch power of -10dBm.
“This is the industry’s highest [QSDP-DD] transmit power,” says Xenos.
The tunable optical filter improves the optical performance of the coherent receiver.
In an optical line system with colourless ROADMs, the Erbium-doped fibre amplifiers (EDFAs) generate out-of-band transmission noise – amplified spontaneous emission (ASE). The noise sources superimpose and become significant, impairing wavelength and system performance dramatically.
The tunable optical filter eliminates this effect and simplifies deployment over any photonics line system. In addition, Ciena says the pluggables can now work alongside high-baud rate transponders in existing ROADM applications.
The QSFP-DD’s tunable optical filter means its optical performance closely matches that of the CFP2-DCO, aiding the two classes of pluggables working together.
Modes of operation
400ZR defines the module’s baseline coherent performance. The OIF developed the 400ZR standard so hyperscalers can link their equipment in two separate data centres up to 120km apart.
The 400ZR specification delivers just enough optical performance to meet the optical link budget. The OIF produced a low-cost, interoperable, pluggable coherent specification.
400ZR supports a single baud rate – 60 gigabaud (GBd), and modulation scheme – dual-polarisation 16-QAM, and carries Ethernet frames.
Google, Meta, Microsoft and Alibaba were all involved in the OIF development, with the 400ZR Implementation Agreement published in early 2020.
400ZR supports two-channel widths: 75GHz and 100GHz, while the forward error correction scheme used is CFEC.
The 400ZR+ MSA enhances the performance by supporting other data rates – 100, 200 and 300 gigabits-per-second (Gbps) – as well as 400Gbps. In addition, it uses several modulation schemes and the enhanced O-FEC error correction scheme that extends reach.
Ciena’s module also meets the OpenROADM MSA, supporting Ethernet and OTN and an enhanced reach at 400Gbps.
Ciena’s Universal module’s extended performance modes up the symbol rate to 65 and 70 gigabaud (GBd) and uses probabilistic constellation shaping (PCS).
PCS maps the bitstream onto the constellation to maximise the data recovery at the coherent receiver, thereby improving overall optical performance. The scheme also allows the fine-tuning of the data rate sent.
At ECOC, Ciena showed the module implementing the high-performance mode at 70GBd and PCS.
ECOC innovation award
The ECOC Exhibition Market Focus Advisory Committee awarded the most innovative product award to Ciena’s WaveLogic 5 Nano 400G Universal QSFP-DD.
Hyperscalers' needs drive a new class of coherent DSP
Coherent digital signal processors (DSPs) companies have supported two families of coherent chips for some time. That’s because no single coherent DSP can meet all the market’s requirements.
The coherent DSP used for highest-performance optical transmissions must include advanced coding techniques, forward error correction, and a high symbol rate to send as much data as possible on a single wavelength and maximise reach.
In contrast, a DSP for coherent pluggable modules needs to be power-efficient and compact to meet the optical module’s power envelope and size constraints; a 400ZR QSFP-DD and a CFP2-DCO 400ZR+ being examples.
According to Ciena, now there is a need for a third category of coherent DSP for 1.6 terabit-per-second (Tbps) and 3.2Tbps transmissions over short distances for next-generation switch routers.
Carrying data centre payloads
The need comes from the hyperscalers, as with most emerging coherent optical applications. The new coherent DSP design is needed since it is the only way to support multi-terabit data rates for this application, says Ciena.
“Data centre switch routers with new 51.2- and 102.4-terabit switch chipsets will need greater than 400 gigabit-per-wavelength connectivity,” said Helen Xenos, senior director, portfolio marketing at Ciena, during a talk at NGON & DCI World, held in Barcelona in June.
The coherent DSP will connect equipment within a data centre and between data centre buildings on campus. A 1-10km reach for the 1.6Tbps or 3.2Tbps wavelength transmissions is needed using an industry-standard pluggable such as a QSFP-DD or a OSFP pluggable form factor.
“It would have to be a specific, very low-cost design,” says Xenos.
Coherent evolution
Applications using coherent optical technology continue to grow.
Subsea, long-haul, metro, and 80-120km data centre interconnect are all well-known markets for coherent optics, said Xenos. Now, coherent is moving to the access network and for unamplified single-channel links.
“There is no one coherent optical design that will be cost-optimal across all of these applications,” said Xenos. “This is why multiple coherent optical modem designs are required.”
Xenos last presented at NGON & DCI World in pre-pandemic 2019. Then, the questions were whether 800-gigabit wavelengths would be needed and what optical performance 400-gigabit coherent pluggables would deliver.
Much has since changed. There has been a broad deployment of optical transport equipment using 800-gigabit wavelengths while the coherent pluggable market has gone from strength to strength.
For the high-end, up to 800 gigabits per wavelength, 7nm CMOS DSPs are used, operating at a symbol rate of 90-110 gigabaud (GBd).
For 400-gigabit coherent pluggables operating, the symbol rate is 60-70GBd, while the optics used is mainly silicon photonics.
800-gigabit market
Ciena started shipping 800-gigabit capable optical modules in April 2020.
Since then, the company has seen strong uptake, with hyperscalers leading the way.
Also, a broad deployment of colourless, flexible grid optical line systems has helped 800-gigabit technology adoption.
Xenos cited, among others, Altibox, which brings high capacity connectivity from Norway to key digital hubs in Europe.
“They turned up the longest 800-gigabit wavelength between Copenhagen and Amsterdam, and that was over 1,100 kilometres,” she said.
400-gigabit pluggables
Xenos points out that there has been a halving of the power-per-bit at 400Gbps.
Source: Ciena.
In 2017, Ciena offered a 400-gigabit 60GBd modem design in a 5×7-inch package.
“Now we have a pluggable 400-gigabit QSFP-DD at 60GBd pluggable, so the same type of design, the same simple feature set required with a 400ZR,” said Xenos.
Optical performance is also being pushed to 70GBd in the QSFP-DD, with the module having a higher output power.
Near-term designs
Ciena says the next two to three generations of coherent DSPs will use 5nm and 3nm CMOS.
New promising materials for optical modulation are emerging, such as thin-film lithium niobite, and barium titanate, which is compatible with silicon photonics.
“[A] Higher baud [rate] will reduce cost-per-bit and get more capacity using a single wavelength,” says Xenos. “Also, there will be more intelligence and programmability as we move forward to enable more automated networks.”
She says a 160GBd symbol rate is needed to send 800 gigabits over long-distance spans.
The key for all the different modem designs is to develop something better while choosing the right technologies so that new products are available promptly.
“It’s essential to make the right technology choice that will give the right reliability and be commercially available,” says Xenos.
Three nanometre CMOS promises more significant performance benefits for a DSP design, but developing the process technology is challenging for the leading chip fabrication plants. In addition, a 3nm CMOS process will be costly.
Award
Ciena won the optical vendor of the year award, one of the five prizes presented at the NGON & DCI World show.
WaveLogic 5: Packing a suitcase of ideas in 7nm CMOS
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Ciena’s WaveLogic 5 coherent digital signal processor family comprises the Extreme and Nano chips
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The WaveLogic 5 Extreme maximises optical capacity and transmission reach while the WaveLogic 5 Nano is targeted at compact, power-conservative applications
Kim Roberts
Advancing coherent optical transmission performance; targeting the emerging coherent pluggable market; selling modules directly, and the importance of being more vertically integrated. All these aspects were outlined by Cisco to explain why it intends to buy the coherent optical transmission specialist, Acacia Communications; a deal that is set to be completed in the spring of 2020.
But such strategic thinking is being pursued by Ciena with its next-generation WaveLogic 5 family of coherent DSPs.
The WaveLogic 5 continues Ciena’s tradition of issuing a coherent digital signal processor (DSP) family approximately every three years: Ciena announced the WaveLogic 3 in 2012 and the WaveLogic Ai in 2016. (Add links).
The company has managed to maintain its three-yearly cadence despite the increasing sophistication of each generation of coherent DSP. For example, the WaveLogic 5 Extreme will support 800 gigabits-per-wavelength, double Ciena’s WaveLogic Ai that has been shipping for nearly two years.
Kim Roberts, vice president of WaveLogic science, says Ciena has managed to deliver its coherent DSPs in a timely manner since much of the algorithmic development work was done 5-6 years ago. The issue has been that certain features developed back then could not be included within the WaveLogic Ai.
WaveLogic 5 is implemented using a 7nm FinFET CMOS process whereas the WaveLogic Ai uses a 28nm specialist CMOS process known as fully-depleted silicon-on-insulator (FD-SOI).
“Seven-nanometer CMOS, due to its density and low heat, allows us to implement things that didn’t make the cut for the WaveLogic Ai,” says Roberts.
The company has a ‘suitcase of ideas’, he says, but not all of the concepts make it into any one generation of chip. “They have to justify performance versus schedule versus heat [generated],” says Roberts. “As we improve the technology, more features make the cut.”
And there are developments that will be included in future designs: “We keep refilling the suitcase,” says Roberts.
NAMING
Ciena first used the Extreme and Nano nomenclature with the WaveLogic 3. In contrast, the WaveLogic Ai, when launched in 2016, was a single-chip targeting the high-end. Ciena chose to change the naming scheme with the Ai since the chip signified a shift with features such as network monitoring.
However, Ciena highlights a key difference between the WaveLogic 3 and WaveLogic 5 families. The WaveLogic 3 Extreme and the WaveLogic 3 Nano could talk to each other on appropriate spans. In contrast, the two WaveLogic 5 chips are distinct. “They are not designed to interwork,” says Roberts.
NETWORKING TRENDS
Telecom service providers are investing in their networks to make them more adaptive. They want their networks to be scalable and programmable, says Ciena.
The operators also want to better understand what is happening in their networks and that requires collecting data, performing analytics and using software to configure their networks in an automated way.
“How do you get there? It is all about coherent technology,” says Helen Xenos, senior director, portfolio marketing at Ciena. “It is a critical element that is helping operators scale their networks.”
By enhancing the traffic-carrying capacity of fibre, coherent technology enables operators to reduce transport costs. “It allows them to be more competitive as they can do more with the hardware they deploy,” says Xenos.
Helen Xenos
Both telcos and cable operators are also applying coherent technology to new applications in their networks such as access.
These transport needs are causing a divergence in requirements.
One is to keep advancing optical performance in terms of the spectral efficiency and the traffic-carrying capacity of links. This is what the WaveLogic 5 Extreme tackles.
The second requirement - producing a compact coherent design for the network edge - is addressed by the WaveLogic 5 Nano.
For access designs, what is important is a compact design where the optics and the DSP can operate over an extended temperature range.
The Nano also addresses the hyperscalers’ need to connect their distributed data centres across a metro. “They need high capacity - 400 gigabits - and short-reach connectivity,” says Xenos. “It really needs to be the smallest footprint to maximise density.”
VERTICAL INTEGRATION
In addition to unveiling the WaveLogic 5 Extreme and Nano ICs, Ciena has outlined how it is more vertically integrated after investing in optics. In 2016, Ciena acquired the high-speed photonics division of Teraxion, gaining expertise in indium phosphide and silicon photonics expertise. {add link}.
Ciena is also now selling coherent optical modules. Gazettabyte revealed last year that Ciena was planning to sell modules using its own optics and WaveLogic technologies. {add link}
The company has no preference regarding indium phosphide and silicon photonics and uses what is best for a particular design.
“Silicon photonics buys you ease-of-manufacturing and cost; indium phosphide is what you need for 800 gigabits,” says Xenos.
Ciena stresses, however, that there is no simple formula as to when each is preferred. In terms of size and heat, silicon photonics has a strong advantage. “In terms of performance, you get better performance in some instances with indium phosphide and then there are overlaps because you bring in cost and other constraints,” says Roberts. “So there is no simple divide.”
“As we move forward, we are going to see an increasing percent of Ciena-custom components in WaveLogic coherent modems,” says Xenos.
Source: Gazettabyte
EXTREME
The WaveLogic 5 Extreme introduces several developments. It operates at specific baud rates ranging from 60 to 95 gigabaud. The baud rates are chosen so that both fixed-grid 100GHz channels and flexible grid ones are supported.
“For the best performance, you have flexible grid when 95 gigabaud is the primary baud rate,” says Roberts.
It is also Ciena’s first coherent DSP that uses probabilistic constellation shaping, a coding scheme used to achieve granular capacity increments. {add link}
“From 200 gigabits to 800 gigabits [in 25-gigabit increments], optimised over any path or the available margin,” says Roberts. “But what is unique about this is that it is optimised for non-linear propagation.”
Initially, the products using the WaveLogic 5 Extreme will use 50-gigabit increments. “This is what is required to service customers’ client requirements today: ten gigabits and multiples of 100-gigabit clients,” says Xenos.
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“With 25-gigabit steps in client rate, the customer can choose to spend the margin on sending more bits”
The DSP uses four-wave frequency-division multiplexing to mitigate non-linear impairments, particularly beneficial for sub-sea systems.
Ciena says the four-wave frequency-division multiplexing is achieved electrically, reducing the optics to a minimum. “One laser and one modulator are used, so all the [cost-saving] economics of a single optical wavelength,” says Roberts. “But it has the non-linear performance of four tightly-coupled electrical systems.”
Ciena has also added an improved forward-error correction (FEC) scheme - a ‘throughput-optimised FEC’ - that uses variable overhead bits depending on the client rate.
“It will handle 8.6 percent errors compared to what we used in the WaveLogic Ai which handles 3.5 percent errors,” says Roberts. “So it is a decibel better.”
The Extreme chip also has improved link-monitoring capabilities. It monitors the signal-to-noise per channel as well as quantifies the non-linear contributions. “It helps people to understand what is happening in the network and create algorithms to optimise the capacity across the network,” says Xenos.
PROBABILISTIC CONSTELLATION SHAPING
Probabilistic shaping is used to improve the optical performance by lowering the signal energy by not using all the constellation points. Unless, that is, the full data rate is used and then all the constellation points are needed.
The degree of probabilistic shaping used is determined for each link. The parameters used to determine the probabilistic shaping are the amount of dispersion on the link, the span’s reach, and the transmitted client rate.
“The modem will measure what is going on in the link and the customer or some higher-level software will say what the client rate is,” says Roberts. “The modem will then figure out how to do the best non-linear probabilistic shaping to support that rate on the link.”
Roberts says other firms’ probabilistic shaping use one symbol at a time whereas Ciena use blocks, each comprising 128 symbols. “A bigger number would be better but I'm limited by my hardware,” says Roberts.
The 128 symbols equate to 1024 bits: four magnitude bits using 64-ary quadrature amplitude modulation (64-QAM) multiplied by two, one for each polarisation.
This means there are a total of 2^1024 combinations of 1024-bit sequences that could be sent. However, when sending a 400 Gigabit Ethernet (GbE) client signaland, for the benefit of explanation, assuming that 555 bits are needed to carry the data payload and the overhead, the number of possible bit sequences is trimmed to 2^555.
This is still a fantastically huge number but the DSP can work out which are the best 555-bit sequences to send based on them having the most tolerance to linear and non-linear interference.
“The ones that play nicely with their neighbours such that they cause the minimum non-linear degradation on the neighbouring wavelengths and on the other symbols,” explains Roberts.
Ciena is not forthcoming as to how it calculates the best sequences. “Ciena’s algorithms decide which ones are best,” says Xenos. “This is one of our key differentiators.”
The result is that, depending on the fibre type, a 1.5dB performance improvement is achieved for the non-linear characteristics.
“It allows more capacity to be chosen by the customer on that same link,” says Roberts. “With 25-gigabit steps in client rate, the customer can choose to spend the margin on sending more bits.”
Operating the Extreme at 95GBd, a reach of 4,000 km is possible at 400 gigabits and at 600 gigabits, the reach is 1,000 km (see table).
WAVELOGIC 5 NANO
The WaveLogic Nano supports 100-gigabit to 400-gigabit wavelengths and is aimed at applications that need compact designs that generate the least heat.
One application is to enable cable operators to move optics closer to the user and that must operate over an extended temperature range. Here, a packet platform is used that will support line interworking as equipment from different vendors may be at each end of the link.
Another requirement is operating over multiple spans in a metro. Here, compact equipment and low power are more important than spectral efficiency but it is still a challenging environment, says Ciena. Hundreds of nodes may be talking to each other and there may be cascaded reconfigurable optical add-drop multiplexers (ROADMs) with different fibre types making up the network.
A third application is single-span data centre interconnect where achieving the highest density on routers is key. This is the application the 400-gigabit, at least 80km 400ZR specification developed by the Open Internetworking Forum will address.
“The design that we are doing for the WaveLogic 5 Nano for 400ZR is to fit into a QSFP-DD,” says Xenos. “If there is a need for an OSFP [pluggable module], we will offer OSFP.”
Ciena also expects to offer a Nano-based CFP2-DCO module, which will outperform the ZR in terms of reach and features, for more demanding metro applications.
Another new segment requiring coherent optics is 4G and 5G access. “It is to be determined what type of platform is the winning solution in this environment,” says Xenos.
MAKING MODULES
Ciena first made its coherent DSP available to third parties in 2017 when it signed an agreement with Lumentum, NeoPhotonics and at the time Oclaro (since acquired by Lumentum) to use its WaveLogic Ai in their modules.
Now Ciena is selling directly the full coherent modem: the DSP and the optics. This is why Ciena created its Optical Microsystems unit in late 2017.
CMOS PROCESS
Moving to a 7nm FinFET CMOS process delivers several benefits.
It generates much lower heat than the WaveLogic Ai’s 28nm FD-SOI process. It also has a lower quiescent current, the current dissipated independent of whether the chip’s logic is active or not. And 7nm CMOS delivers much greater circuit density: the functionality that can be crammed into a square micrometre of silicon.
“So, a low power [consumption] on features you are not using, and we can include features that if you can't afford the heat, you can turn them off,” says Roberts.
It will offer its Nano in the form of pluggable modules, the WaveLogic Ai as a 5x7-inch module, and the WaveLogic 5 Extreme in another module form factor that will have its own interface. “These would all be viable optics,” says Xenos.
Availability
The first Wave Logic 5 Nano products will appear in the second half of this year while the first Extreme-based products will be available at the end of this year. The 400ZR coherent pluggable module is expected to be available in the first half of 2020.
Ciena goes stackable with 8180 'white box' and 6500 RLS
Ciena has unveiled two products - the 8180 coherent networking platform and the 6500 reconfigurable line system - that target cable and cellular operators that are deploying fibre deep in their networks, closer to subscribers.
The 6500 line system is also aimed at the data centre interconnect market given how the webscale players are experiencing a near-doubling of traffic each year.
Source: Ciena
The cable industry is moving to a distributed access architecture (DAA) that brings fibre closer to the network’s edge and splits part of the functionality of the cable modem termination system (CMTS) - the remote PHY - closer to end users. The cable operators are deploying fibre to boost the data rates they can offer homes and businesses.
Both Ciena’s 8180 modular switch and the 6500 reconfigurable line system are suited to the cable network. The 8180 is used to link the master headend with primary and secondary hub sites where aggregated traffic is collected from the digital nodes (see network diagram). The 8180 platforms will use the modular 6500 line system to carry the dense wavelength-division multiplexed (DWDM) traffic.
“The [cable] folks that are modernising the access network are not used to managing optical networking,” says Helen Xenos, senior director, portfolio marketing at Ciena (pictured). “They are looking for simple platforms, aggregating all the connections that are coming in from the access.”
The 8180 can play a similar role for wireless operators, using DWDM to carry aggregated traffic for 4G and 5G networks.
Ciena says the 6500 optical line system will also serve the data centre interconnect market, complementing the WaveServer Ai, Ciena’s second-generation 1RU modular platform that has 2.4 terabits of client-side interfaces and 2.4 terabits of coherent capacity.
With the 8180, you are only using the capacity on the fibre that you have traffic for
“They [the webscale players] are looking for as many efficiencies as they can get from the platforms they deploy,” says Xenos. “The 6500 reconfigurable line system gives them the flexibility they need - a colourless, directionless, contentionless [reconfigurable optical add-drop multiplexer] and a flexible grid that extends to the L-band.”
A research note from analyst house, Jefferies, published after the recent OFC show where Ciena announced the platforms, noted that in many cable networks, 6-strand fibre is used: two fibre pairs allocated for business services and one for residential. Adding the L-band to the existing C-band effectively doubles the capacity of each fibre pair, it noted.
The 8180
Ciena’s 8180 is a modular packet switch that includes coherent optics. The 8180 is similar in concept to the Voyager and Cassini white boxes developed by the Telecom Infra Project. However, the 8180 is a two-rack-unit (2RU) 6.4-terabit switch compared to the 1RU, 2-terabit Voyager and the 1.5RU 3.2-terabit Cassini. The 8180 also uses Ciena’s own 400-gigabit coherent DSP, the WaveLogic Ai, rather than merchant coherent DSP chips.
The platform comprises 32 QSFP+/ QSFP28 client-side ports, a 6.4-terabit switch chip and four replaceable modules or ‘sleds’, each capable of accommodating 800 gigabits of capacity. The options include an initial 400-gigabit line-side coherent interface (a sled with two coherent WaveLogic Ai DSPs will follow), an 8x100-gigabit QSFP28 sled, a 2x400-gigabit sled and also the option for an 800-gigabit module once they become available.
Source: Ciena
Using all four sleds as client-side options, the 8180 becomes a 6.4-terabit Ethernet switch. Using only coherent sleds instead, the packet-optical platform has a 1.6-terabit line-side capacity. And because there is a powerful switch chip integrated, the input ports can be over-subscribed.“With the 8180, you are only using the capacity on the fibre that you have traffic for,” says Xenos.
6500 line system
The 6500 reconfigurable line system is also a modular design. Aimed at the cable, wireless, and data centre interconnect markets, only a subset of Ciena’s existing optical line systems features is used.
“The 6500 software has a lot of capabilities that the content providers are not using,” says Xenos. “They just want to use it as a photonic layer.”
There are three 6500 reconfigurable line system platform sizes: 1RU, 2RU and 4RU. The chassis can be stacked and managed as one unit. Card options that fit within the chassis include amplifiers and reconfigurable optical add-drop multiplexers (ROADMs).
The amplifier options area dual-line Erbium-doped fibre amplifiercard that includes an integrated bi-directional optical time-domain reflectometer (OTDR) used to characterise the fibre. There is also a half-line-width RAMAN amplifier card. The line system will support the C and L bands, as mentioned.
The reconfigurable line system also has ROADM cards: a 1x12 wavelength-selective switch (WSS) with integrated amplifier, a colourless 16-channel add-drop that support channels of any size (flexible grid), and a full-width card 1x32 WSS. “The 1x32 would be used for colourless, directionless and directionless [ROADM] configurations,” says Xenos.
The 6500 reconfigurable line system also supports open application porgramming interfaces (APIs) for telemetry, with a user able to program the platform to define the data streamed.“The platform can also be provisioned via REST APIs; something a content provider will do,” she says.
Ciena is a member of the OpenROADM multi-source agreement and was involved in last year’s AT&T OpenROADM trial with its 6500 Converged Packet Optical Transport (POTS) platform.
Will the 6500 reconfigurable line system be OpenROADM-compliant?
“This card [and chassis form factor] could be used for OpenROADM if AT&T preferred this platform to the other [6500 Converged POTS] one,” says Xenos. “You also have to design the hardware to meet the specifications for OpenROADM.”
Ciena expects both platforms to be available by year-end. The 6500 reconfigurable line system will be in customer trials at the end of this quarter while the 8180 will be trialed by the end of the third quarter.
Verizon, Ciena and Juniper trial 400 Gigabit Ethernet
Verizon has sent a 400 Gigabit Ethernet signal over its network, carried using a 400-gigabit optical wavelength.
The trial’s goal was to demonstrate multi-vendor interoperability and in particular the interoperability of standardised 400 Gigabit Ethernet (GbE) client signals.
Glenn Wellbrock“[400GbE] Interoperability with the client side has been the long pole in the tent - and continues to be,” says Glenn Wellbrock, director, optical transport network - architecture, design and planning at Verizon. “This was trial equipment, not generally-available equipment.”
It is only the emergence of standardised modules - in this case, an IEEE 400GbE client-side interface specification - that allows multi-vendor interoperability, he says.
By trialing a 400-gigabit lightpath, Verizon also demonstrated the working of a dense wavelength-division multiplexing (DWDM) flexible grid, and a baud rate nearly double the 32-35Gbaud in wide use for 100-gigabit and 200-gigabit wavelengths.
“It shows we can take advantage of the entire system; we don’t have to stick to 50GHz channel spacing anymore,” says Wellbrock.
[400GbE] Interoperability with the client side has been the long pole in the tent - and continues to be
Trial set-up
The trial used Juniper Networks’ PTX5000 packet transport router and Ciena’s 6500 packet-optical platform, equipment already deployed in Verizon’s network.
The Verizon demonstration was not testing optical transmission reach. Indeed the equipment was located in two buildings in Richardson, within the Dallas area. Testing the reach of 400-gigabit wavelengths will come in future trials, says Wellbrock.
The PTX5000 core router has a traffic capacity of up to 24 terabits and supports 10-gigabit, 40-gigabit and 100-gigabit client-side interfaces as well as 100-gigabit coherent interfaces for IP-over-DWDM applications. The PTX5000 uses a mother card on which sits one or more daughter cards hosting the interfaces, what Juniper calls a flexible PIC concentrator (FPC) and physical interface cards (PICs), respectively.
Juniper created a PIC with a 400GbE CFP8 pluggable module implementing the IEEE’s 10km 400GBASE-LR8 standard.
“For us, it was simply creating a demo 400-gigabit pluggable line card to go into the line card Verizon has already deployed,” says Donyel Jones-Williams, director of product marketing management at Juniper Networks.
Donyel Jones-WilliamsThe CFP8 400GbE interface connected the router to Ciena’s 6500 packet-optical platform.
Ciena also used demonstration hardware developed for 400-gigabit trials. “We expect to develop other hardware for general deployment,” says Helen Xenos, senior director, portfolio marketing at Ciena. “We are looking at smaller form-factor pluggables to carry 400 Gigabit Ethernet.”
400-gigabit deployments and trials
Ciena started shipping its WaveLogic Ai coherent modem that implements 400-gigabit wavelengths in the third quarter of 2017. Since then, the company has announced several 400-gigabit deployments and trials.
Vodafone New Zealand deployed 400 gigabits in its national transport network last September, a world first, claims Ciena. German cable operator, Unitymedia, has also deployed Ciena’s WaveLogic Ai coherent modem to deliver a flexible grid and 400-gigabit wavelengths to support growing content delivered via its data centres. And JISC, which runs the UK’s national research and education network, has deployed the 6500 platform and is using 400-gigabit wavelengths.
Helen Xenos
Last September, AT&T conducted its own 400-gigabit trial with Ciena. With AT&T’s trial, the 400-gigabit signal was generated using a test bed. “An SDN controller was used to provision the circuit and the [400-gigabit] signal traversed an OpenROADM line system,” says Xenos.
Using the WaveLogic Ai coherent modem and its support for a 56Gbaud rate means that tunable capacity can now be doubled across applications, says Xenos. The wavelength capacity used for long-haul distances can now be 200 gigabits instead of 100 gigabits, while metro-regional networks spanning 1,000km can use 300-gigabit wavelengths. Meanwhile, 400-gigabit lightpaths suit distances of several hundred kilometres.
It is the large data centre operators that are driving the majority of 400 gigabit deployments, says Ciena. The reason the 400-gigabit announcements relate to telecom operators is because the data centre players have not gone public with their deployments, says Xenos.
Juniper Networks’ PTX5000 core router with 400GbE interfaces will primarily be used by the telecom operators. “We are in trials with other providers on 400 gigabits,” says Jones-Williams. “Nothing is public as yet.”
Real-time visibility makes optical networking smarter
Systems vendors are making optical networks smarter. Their latest equipment, combining intelligent silicon and software, can measure the status of the network and enable dynamic network management.
Ciena recently announced its Liquid Spectrum networking product while Infinera has launched its Instant Network. Both vendors exploit the capabilities of their latest generation coherent DSPs to allow greater network automation and efficiency. The vendors even talk about their products being an important step towards autonomous or cognitive networks.
"Operators need to do things more efficiently," says Helen Xenos, director, portfolio solutions marketing at Ciena. "There is a lot of unpredictability in how traffic needs to be connected over the network." Moreover, demands on the network are set to increase with 5G and the billions of devices to be connected with the advent of Internet of Things.
Existing optical networks are designed to meet worse-case conditions. Margins are built into links based on the fibre used and assumptions are made about the equipment's end-of-life performance and the traffic to be carried. Now, with Ciena's latest WaveLogic Ai coherent DSP-ASIC, not only is the performance of the network measured but the coherent DSP can be used to exploit the network's state rather than use the worse-case end-of-life conditions. "With Liquid Spectrum, you now don't need to operate the network in a static mode," says Xenos.
We are at the beginning of this new world of operating networks
Software applications
Ciena has announced the first four software applications as part of Liquid Spectrum. The first, Performance Meter, uses measured signal-to-noise ratio data from the coherent DSP-ASICs to gauge the network's state to determine how efficiently the network is operating.
Bandwidth Optimiser acts on the network planner's request for bandwidth. The app recommends the optimum capacity that can be run on the link, based on exploiting baud rate and the reach, and also where to place the wavelengths within the C-band spectrum. Moreover, if service demands change, the network engineer can decide to reduce the built-in margins. "I may decide I don't need to reserve a 3dB margin right now and drop it down to 1dB," says Xenos. Bandwidth Optimiser can then be rerun to see how the new service demand can be met.
This approach contrasts with the existing way end points are connected, where all the wavelengths used are at the same capacity, a user decides their wavelengths and no changes are made once the wavelengths are deployed. "It is much simpler, it [the app] takes away complexity from the user," says Xenos.
The Liquid Restoration app ensuring alternative capacity in response to the loss of a 300-gigabit route due to a fault. Source: Ciena
The two remaining apps launched are Liquid Restoration and Wave-Line Synchroniser. Liquid Restoration looks at all the available options if a particular path fails. "It will borrow against margin to get as much capacity as possible," says Xenos. Wave-Line Synchroniser is a tool that helps with settings so that Ciena's optics can work with another vendor's line system or optics from another vendor work with Ciena's line system.
Liquid Spectrum will be offered as a bundle as part of Ciena's latest BluePlanet Manage, Control and Plan tool that combines service and network management, resource control and planning.
Xenos says Liquid Spectrum represents the latest, significant remaining piece towards the industry's goal of developing an agile optical infrastructure. Sophisticated reconfigurable optical add-drop multiplexers (ROADMs) and flexible coherent DSPs have existed for a while but how such flexible technology has been employed has been limited because of the lack of knowledge of the real-time state of the network. Moreover, with these latest Liquid Spectrum software tools, much of the manual link engineering and complexity regarding what capacity can be supported and where in the spectrum it should be placed, says Xenos.
"We are at the beginning of this new world of operating networks," says Xenos. "Going forward, there will be an increasingly level of sophistication that will be built into the software."
Ciena demonstrated Liquid Spectrum at the OFC show held in Los Angeles last month.
Part 2: Infinera's Instant Network, click here
Ciena brings data analytics to optical networking
- Ciena's WaveLogic Ai coherent DSP-ASIC makes real-time measurements, enabling operators to analyse and adapt their networks.
- The DSP-ASIC supports 100-gigabit to 400-gigabit wavelengths in 50-gigabit increments.
- The WaveLogic Ai will be used in Ciena’s systems from 2Q 2017.
Ciena has unveiled its latest generation coherent DSP-ASIC. The device, dubbed WaveLogic Ai, follows Ciena’s WaveLogic 3 family of coherent chips which was first announced in 2012. The Ai naming scheme reflects the company's belief that its latest chipset represents a significant advancement in coherent DSP-ASIC functionality.
Helen XenosThe WaveLogic Ai is Ciena's first DSP-ASIC to support two baud rates, 35 gigabaud for fixed-grid optical networks and 56 gigabaud for flexible-grid ones. The design also uses advanced modulation schemes to optimise the data transmission over a given link.
Perhaps the most significant development, however, is the real-time network monitoring offered by the coherent DSP-ASIC. The data will allow operators to fine-tune transmissions to adapt to changing networking conditions.
“We do believe we are taking that first step towards a more automated network and even laying the foundation for the vision of a self-driving network,” says Helen Xenos, director, portfolio solutions marketing at Ciena.
All those assumptions of the past [based on static traffic] aren't holding true anymore
Network Analytics
Conservative margins are used when designing links due to a lack of accurate data regarding the optical network's status. This curtails the transmission capacity that can be sent since a relatively large link margin is used. In turn, cloud services and new applications mean networks are being exercised in increasingly dynamic ways. “The business environment has changed a little bit,” says Joe Cumello, vice president, portfolio marketing at Ciena. “All those assumptions of the past [based on static traffic] aren't holding true anymore.”
Ciena is being asked by more and more operators to provide information as to what is happening within their networks. Operators want real-time data that they can feed to analytics software to make network optimisation decisions. "Imagine a network where, instead of those rigid assumptions in place, run on manual spreadsheets, the network is making decisions on its own," says Cumello.
WaveLogic Ai performs real-time analysis, making available network measurements data every 10ms. The data can be fed through application programming interfaces to analytics software whose output is used by operators to adapt their networks.
Joe Cumello
The network parameters collected include the transmitter and receiver optical power, polarisation channel and chromatic dispersion conditions, error rates and transmission latency. In addition, the DSP-ASIC separates the linear and non-linear noise components of the signal-to-noise ratio. An operator will thus see what the network margin is and allow links to operate more closely to the limit, improving transmissions by exploiting the WaveLogic Ai's 50-gigabit transmission increments.
"Maybe there are only a few wavelengths in the network such that the capacity can be cranked up to 300 gigabits. But as more and more wavelengths are added, if you have the tools, you can tell the operator to adjust,” says Xenos. “This helps them get to the next level; something that has not been available before.”
WaveLogic Ai
The WaveLogic Ai's lower baud rate - 35 gigabaud - is a common symbol rate used by optical transmission systems today. The baud rate is suited to existing fixed-grid networks based on 50GHz-wide channels. At 35 gigabaud, the WaveLogic Ai supports data rates from 100 to 250 gigabits-per-second (Gbps).
The second, higher 56 gigabaud rate enables 400Gbps single-wavelength transmissions and supports data rates of 100 to 400Gbps in increments of 50Gbps.
Using 35 gigabaud and polarisation multiplexing, 16-ary quadrature amplitude modulation (PM-16QAM), a 200-gigabit wavelength has a reach is 1,000km.
With 35-gigabaud and 16-QAM, effectively 8 bits per symbol are sent.
In contrast, 5 bits per symbol are used with the faster 56 gigabaud symbol rate. Here, a more complex modulation scheme is used based on multi-dimensional coding. Multi-dimensional formats add additional dimensions to the four commonly used based on real and imaginary signal components and the two polarisations of light. The higher dimension formats may use more than one time slot, or sub-carriers in the frequency domain, or even use both techniques.
For the WaveLogic Ai, the 200-gigabit wavelength at 56 gigabaud achieves a reach of 3,000km, a threefold improvement compared to using a 35 gigabaud symbol rate. The additional reach occurs because fewer constellation points are required at 56 gigabaud compared to 16-QAM at 35 gigabaud, resulting in a greater Euclidean distance between the constellation points. "That means there is a higher signal-to-noise ratio and you can go a farther distance," says Xenos. "The way of getting to these different types of constellations is using a higher complexity modulation and multi-dimensional coding."
We do believe we are taking that first step towards a more automated network and even laying the foundation for the vision of a self-driving network
The increasingly sophisticated schemes used at 56 gigabaud also marks a new development whereby Ciena no longer spells out the particular modulation scheme used for a given optical channel rate. At 56 gigabaud, the symbol rate varies between 4 and 10 bits per symbol, says Ciena.
The optical channel widths at 56 gigabaud are wider than the fixed grid 50GHz. "Any time you go over 35 gigabaud, you will not fit [a wavelength] in a 50GHz band," says Xenos.
The particular channel width at 56 gigabaud depends on whether a super-channel is being sent or a mesh architecture is used whereby channels of differing widths are added and dropped at network nodes. Since wavelengths making up a super-channel go to a single destination, the channels can be packed more closely, with each channel occupying 60GHz. For the mesh architecture, guard bands are required either side of the wavelength such that a 75GHz optical channel width is used.
The WaveLogic Ai enables submarine links of 14,000km at 100Gbps, 3,000km links at 200Gbps (as detailed), 1,000km at 300Gbps and 300km at 400Gbps.
Hardware details
The WaveLogic Ai is implemented using a 28nm semiconductor process known as fully-depleted silicon-on-insulator (FD-SOI). "This has much lower power than a 16nm or 18nm FinFET CMOS process," says Xenos. (See Fully-depleted SOI vs FinFET)
Using FD-SOI more than halves the power consumption compared to Ciena’s existing WaveLogic 3 coherent devices. "We did some network modelling using either the WaveLogic 3 Extreme or the WaveLogic 3 Nano, depending on what the network requirements were," says Xenos. "Overall, it [the WaveLogic Ai] was driving down [power consumption] more than 50 percent." The WaveLogic 3 Extreme is Ciena's current flagship coherent DSP-ASIC while the Nano is tailored for 100-gigabit metro rates.
Other Ai features include support for 400 Gigabit Ethernet and Flexible Ethernet formats. Flexible Ethernet is designed to support Ethernet MAC rates independent of the Ethernet physical layer rate being used. Flexible Ethernet will enable Ciena to match the client signals as required to fill up the variable line rates.
Further information:
SOI Industry Consortium, click here
STMicroelectronics White Paper on FD-SOI, click here
Other coherent DSP-ASIC announcements in 2016
Infinera's Infinite Capacity Engine, click here
Nokia's PSE-2, click here