Market Adoption and Use Case Expansion
Coherent pluggables have seen remarkable market adoption, with 400G ZR/ZR+ coherent optics becoming the most widely adopted coherent technology in history. While some in the industry predicted early on that 400ZR pluggables would only be a small portion of the coherent market, Acacia has been laser focused on bringing these solutions to its customers to deliver the architectural change needed to transform networks to meet ever-growing bandwidth demands. As a result, Acacia is a market leader in shipments of 400G+ coherent pluggables.

During 2024, Acacia expanded this market-leading portfolio with the introduction of 800ZR and 800G ZR+ pluggables with Interoperable PCS in QSFP-DD and OSFP form factors. These solutions have already been proven in field trials, with Colt being the first provider to successfully trial enhanced performance 800G ZR+ coherent pluggable optics. These 800G router-based optics provide the capability to double Colt’s packet core capacity per link while reducing power per bit by 33.3%.

Acacia also introduced a 400G Ultra Long Haul QSFP-DD module for expanding 400G applications from DCI/metro to long haul applications. The 400G UHL has been proven in field trials, with Arelion announcing that it completed a live network field trial on its route from Chicago to Denver that demonstrated successful IP transmission at a spectrum of 112.5 gigahertz over 2,253 kilometers, with healthy margins, providing longer transmission distances and greater cost savings than currently deployed transponders. Acacia’s 400G ULH pluggables enable Arelion to reduce CAPEX by 35 percent and OPEX costs by 84 percent when expanding its network, providing wider reach with high capacities that support customers’ AI/ML and cloud applications.

The Terabit Era is Going Strong
According to Cignal AI, in 2025, 1.2T+ performance optimized solutions will contribute significantly to bandwidth growth as those solutions continue to be introduced. Acacia’s 1.2T Coherent Interconnect Module 8 (CIM 8), powered by the Jannu DSP, has proven its outstanding performance with multiple record-breaking field trials across Metro, Long Haul and Subsea with Microsoft, Verizon, Windstream, and others. Acacia is also engaged with multiple webscale customers and expects CIM 8 to continue its ramp in 2025.

Looking Ahead…..Artificial Intelligence, 1600ZR/ZR+ and More!
AI certainly was a hot topic during OFC and ECOC in 2024 and Acacia believes it will continue to be in 2025. While a year ago, the industry was focused on single-site AI clusters, we will begin to hear more about methods for distributing AI training over different locations in 2025. And while there is still a lot of work to happen in this area, the optics industry is well positioned to be at the forefront of this evolution since higher speed optical interconnections will be necessary to mitigate bandwidth constraints within an AI networks. Read this recent blog for more information on future proofing your network for AI.

Router-based Coherent Optics
The proliferation of router-based coherent optics is paving the way to a converged IP+Optical network architecture. The benefits in 2024 were clear. Infrastructure provider Colt Technology Services reported a stunning 97% energy savings, and Arelion saved 64% in CapEx and 76% in OpEx. In 2025, we can expect to see more providers leveraging this architecture to achieve increased capacity, reduced energy consumption, and lowered network costs, complexity, and footprint.

1600ZR and 1600ZR+ Standards Agreement
The OIF launched efforts last year on 1.6T coherent optical interconnect solutions and is making progress towards interoperable 1600ZR and 1600ZR+ implementation agreements.  In 2025, the industry will be looking at ways to advance this migration using advanced technologies for high baud rate modulation and smaller CMOS nodes.

Looking to the Future
Acacia is looking forward to another year of industry-wide innovation. Helping to solve some of our customers’ most challenging problems has been part of our DNA since Acacia was founded in 2009 and as you can see from this historic timeline, we have continued to set new benchmarks for performance and efficiency. These innovations are not only addressing the current demands of high capacity networks, but are also paving the way for future growth and scalability. Key to this success has been listening to our customers and designing the products and features that they need to be successful. We look forward to continuing that tradition.

Arelion Achieves 64% CAPEX and 76% OPEX Savings Enabled by Bright 400ZR+ Deployment

In August 2023, Arelion announced that it has taken another landmark step in converging its IP and optical layers as the first global network to deploy 400G QSFP-DD ZR+ Bright coherent optical modules in its production #1 ranked IP backbone. This first regional reach deployment spans 675 kilometers between Stockholm and Copenhagen over third-party Optical Open Line System (O-OLS). According to Arelion, the streamlined architecture eliminates the need for excessive hardware, thereby reducing potential points of failure. As a result, it achieves 64% CAPEX and 76% OPEX savings. This contributes to a significantly more cost-efficient network with fewer interfaces to control and maintain.

Highlighting the benefits of these modules, Arelion’s Mattias Fridström shares his insights in this video from testing the technology to how they can potentially transform network infrastructures.

Mattias Fridström, Vice President & Chief Evangelist at Arelion shares the benefits of deploying Acacia’s 400G QSFP-DD Bright Optical Modules in Arelion’s production IP backbone

Dariusz Solowiej, VP Network Technology & Customer Operations at Arelion added, “With constantly rising demand for our IP services and increasing traffic across the Internet, Arelion is constantly looking to deploy the latest technology. The deployment of 400G QSFP-DD Bright Optical Modules will ensure cost-effective, high-performance connectivity for our customers and help us grow our network in scale as we continue to connect the world. In addition, the coherent pluggable modules also help us achieve our sustainability goals through improved energy efficiency and redeploying redundant hardware assets.”

CENIC Validates Coherent Pluggable Optics for Big Data Applications
Using Bright QSFP-DD coherent optics, the Corporation for Education Network Initiatives in California (CENIC) turned up a 300 Gbps optical service over CENIC’s production line system between Los Angeles and Sunnyvale and confirmed the error-free performance of the service with a comfortable operating margin.

According to CENIC, the new-generation coherent pluggables integrate an amplifier, making it possible to transmit from the optic at power levels that match those of typical transponder line cards. As a result, external amplification is no longer needed to boost the power level transmitted from the optic before it reaches the optical line system.  As explained by Sana Bellamine, CENIC’s Director of Regional and International Infrastructure, “The elimination of the external amplification requirement is an important step toward simplifying the provisioning of optical services and facilitates the adoption of coherent pluggables over our production line system.”

CENIC Validation Setup Diagram with Bright ZR+ Coherent Pluggables with Integrated Amplifiers

Announced earlier this year, Vodafone Turkey and Sipartech trials are summarized in this article.

Bright 400ZR+ QSFP-DD Modules Expands Applications by Enabling Longer Reach Applications
With an optical transmit power at least 10X greater than 400ZR, Bright QSFP-DD modules enable network operators to expand applications that can be addressed by 400G coherent pluggables in router-based optical deployments to include brownfield and greenfield metro/regional networks with reconfigurable optical add-drop multiplexer (ROADM) nodes.

Bright 400ZR+ QSFP-DD modules expand applications of 400G coherent pluggable to brownfield and greenfield metro/regional networks with ROADM nodes.

Visit Us at ECOC OIF 400ZR+ Interop Demonstration
If you are attending ECOC and want to see the Acacia Bright ZR+ coherent module in action, check out the 400ZR+ optics interoperability demonstration at the OIF Booth #304.  We hope you see you there!

Additional Resources

• Blog: Brightening ROADM Networks
• Product Page: Bright 400ZR+ coherent pluggable QSFP-DD module

At the same time, network operators are adopting higher speed interfaces.  Since last year’s conference, we’ve continued to see the aggressive ramp of 400 Gigabits per second (G) pluggables as they’ve made their way into new markets and applications. While coherent pluggables have been migrating towards shorter reaches for quite some time, customers are now increasingly interested in using them for long-haul applications traditionally serviced by embedded coherent modules.  While the high-performance embedded market continues to be strong today, we expect the trend towards pluggables to continue in the future as service providers take advantage of their low power, small size and performance wherever they can.  Standards bodies are looking to define both 800G and higher performing 400G interop modes for next generation MSA pluggable optics.

Coherent pluggable ports are expected to exceed embedded ports in 2023.

 Acacia had the honor of participating in 13 sessions and 2 interoperability demonstrations at this year’s OFC.  Below is a recap of three of the sessions presented in the Market Watch Theater that reinforce the trends toward higher speed interfaces and expected transition from embedded modules to pluggables including industry standardization advancements.

OIF Panel: Defining 800ZR and 800LR; An OIF Update

Tom Williams, Acacia’s Sr. Director, Technical Marketing, gave an Optical Interoperability Forum (OIF) update on 800ZR and 800LR standardization progress. Tom highlighted the rapid success that has been achieved with 400G pluggables and what’s happening next in the standards bodies.

400G Developments Continue
The 400G developments continue in three areas.  The first is ongoing deployments of high transmit power 400G ZR+ QSFP-DD pluggables that support OpenZR+ and Open ROADM modes.  These modules expand the use cases for 400G QSFP-DD pluggables to metro and regional ROADM networks and enable increased transponder density in transport equipment. The second is 400G ER1 which targets 40km point-to-point applications.  The third area is standardization and development of 400G long-haul.

400G developments continue with high TX power 400G ZR+, 400G ER1, and 400G long haul pluggable modules.

800G Standardization in Progress
The current focus of standardization is on 800LR/ZR and Open ROADM products. Network operators are looking for higher baud rate pluggables to take advantage of improvements in cost and power. Increasing baud rates has become an efficient way to enable more cost-effective optical networks by reducing the number of optics needed to support a given transmission capacity.

Focusing next on 800ZR standardization, Tom highlighted how these considerations are like 400ZR, but different. While 800ZR has the potential for more varied use cases depending on the network operator, some are waiting for 1.6T solutions. The key assumptions are that 800ZR will include 16QAM modulation at 118Gbaud, which is double the 400ZR baud rate.  On the receiver side, Open Forward Error Correction, or oFEC, has been selected for improved Optical Signal to Noise Ratio (OSNR) sensitivity and the minimum input power is higher at 118Gbaud. On the transmitter side, there is recognition that the 400G market now includes both amplified and unamplified configurations and co-existence with 400ZR on the same line system requires 3dB higher transmit power for 800ZR.  Tom also highlighted three different transmitter power ranges that have been proposed with each option having use cases that bring value to the market.  These include:

• -11 to -14dBm: Lowest Cost
• -7 to -11dBm: Co-exist with 400ZR
• 0 to -7dBm: Co-exist with traditional DWDM

800G and Beyond Pluggable Coherent – Building on the Success of 400G

Torben Nielsen, Acacia’s Product Line Manager, Pluggable Modules and Distinguished Engineer, also kicked off his presentation by highlighting the 400ZR/ZR+ success story. As the fastest ramping coherent technology to date, these modules benefitted greatly from the work done early on with industry standards.

400G pluggables have been the fastest ramping coherent technology to date.

 Standardization and Vendor Interoperability
Standardization of optical networking technology helps network operators by providing simplicity, interoperability and volume-driven cost. Torben explained that, in the 400G pluggable market, standardization started with 400ZR and quickly evolved as carriers demanded higher performance. This led to the creation of both the Open ROADM and OpenZR+ MSAs.  As a result, today we are seeing 400G pluggables being used across a wide range of applications, using the same component technology throughout each form factor.

The 400ZR/ZR+ success story was enabled in part by standardization and interoperability resulting in 400G pluggables being used across a wide range of applications.  

Torben also discussed how 400ZR/ZR+ leveraged advancements in co-packaging and how these developments are now being extended to future product development using the same common platform that leverages silicon photonics. For example, the same packaging technology that Acacia used in its highly successful 400G pluggable products is now being utilized in its CIM 8 module, which is enabling a pluggable performance optimized solution operating up to 140Gbaud. Acacia will continue leveraging this same approach for future generations such as 800G and 1.6T modules.

800G Coherent Pluggables
Torben next shared how the industry is already looking ahead to 800G pluggables, with first deployments expected in 2024. Currently, 800ZR/LR is being defined in OIF, as Tom shared in his OIF update, with 118Gbaud 16QAM modulation. 800ZR+ will need standardized media interface specification which will likely be 131Gbaud PCS modulation.  Acacia’s silicon photonics can support all transmission rates proposed for both 800ZR and 800ZR+. The high transmit power version can be supported similar to the 400G Bright ZR+ high transmit (TX) power pluggable module.

800G will likely come in ZR, ZR+, and LR versions.

1.6T Coherent Pluggables
In terms of 1.6 coherent pluggables, Torben suggested they are likely needed in the 2025 timeframe or later. He believes 240Gbaud single carrier pluggable is feasible and can have the best potential cost structure with fewer optical components than multi-carrier approaches. There are several engineering challenges to overcome when developing these products including signal integrity, power and thermal design, but the industry has a great track record when it comes to overcoming these challenges.

1.6T coherent pluggables are expected to emerge in the 2025+ timeframe and much work is yet to be done for that to happen.

Market Watch Panel IV: Performance-Centric Long Haul

Anuj Malik, Acacia’s Director, Product Management & Strategy, gave an overview of performance-centric coherent modules. The primary goal of these modules has been to help reduce CapEx and OpEx for network operators. Transceiver cost per bit and number of regenerations are the key CapEx drivers.  Power, footprint and manageability are the key OpEx drivers.

Key to these solutions has been the development of features such as probabilistic constellation shaping (PCS), adaptive baud rate, and advanced compensation algorithms. These technology innovations give service providers unprecedented transmission flexibility to match their network’s architecture, optimize fiber utilization, and simplify deployment.

Performance-centric solutions leverage key technology innovations that provide “knobs” for dialing in performance. 

Anuj also discussed the implications of approaching the Shannon limit, where spectral efficiency gains are only incremental. The focus has been on reducing cost, power and footprint. This will require doubling the baud rate with every generation, designing efficient network architectures and leveraging the benefits of silicon photonics and advanced packaging techniques that can be leveraged across multiple generations of products.

The path to creating cost and power efficient coherent transceivers includes significant increases in capacity and density while reducing power, continued integration, and packaging techniques.

As mentioned earlier, these “terabit era” products were highlighted at this year’s OFC, led by Acacia’s CIM 8 module, with field trials having been announced by China Mobile, NYSERNet and Windstream Wholesale. By leveraging common development approaches with the 400G pluggable modules and Acacia’s proprietary DSP algorithms, the operational benefits of pluggability were brought to the performance-centric multi-haul market segment.  Acacia believes the industry may continue migrating performance-centric towards pluggable modules to take advantage of high performance and power efficiency. This may include the development of high performance 400G long haul pluggables and 800ZR+ with up to 131Gbaud.

Below is a recap of each speaker’s presentation. You can also watch the replay by registering at this link.

400ZR Evolution:  Not Just for DCI Use Cases Anymore
Sterling explained how 400ZR is a specific technology standard and implementation agreement that was defined by OIF after many years in the making. The key goals were interoperability and reducing power, size and cost in order to fit coherent optics inside client-sized routers and switches. Initial buyers were the large hyperscalers, which was key for driving volume. However, the technology has quickly evolved to also address the requirements of communication service providers (CSPs) who have much broader needs beyond point-to-point connectivity.

Figure 1:  Initially addressing volume hyperscalers, pluggables now meet the diverse needs of CSPs.

400G Pluggables Leverage the Same Component Technology Across Many Applications
Looking back to the original DCI use case, Tom Williams, Sr. Director of Marketing for Acacia, recounted how the industry was able to capitalize on an opportunity to bring the power of coherent into the same form factor as client optics. The key was finding the “sweet” spot in terms of the performance needed to cover a large number of applications. “Fortunately, the work on standardization was started early enough so vendors could start developing them and hit the market at just the right time,” he said.

Figure 2:  Industry standardization efforts drove expansion of 400G pluggable use cases.

As a result, today we are seeing 400G pluggables being used across a wide range of applications, leveraging the same component technology throughout each form factor. This has allowed coherent pluggables to expand from the original DCI use case and into service provider networks such as point-to-point, ROADM, campus, enterprise, and even space.

Figure 3:  Acacia’s comprehensive 400G pluggable portfolio addresses a wide range of hyperscale and service provider applications.

400G Pluggables are Powering Comcast’s Core and Access Networks
Venk Mutalik, Fellow at Comcast, started his presentation by giving a brief overview of the Comcast network. While they have a very large core metro footprint, their access network has 3X the fiber mileage compared to the core, making it a very rich fiber environment. Today, 400G pluggables are in the core and the metro and they expect them to become even more important in the future.

Figure 4:  Comcast deploys many different 400G pluggable form factors throughout its network

For Comcast’s access network, they view this as converged platform that can handle both business and residential services. It is the 100G Bi-Directional CFP-2 pluggable modules that are enabling Comcast to use the access footprint to provide these combined services on one single fiber.

Figure 5: 100G Bi-Directional CFP-2 pluggable modules enable Comcast to combine business and residential services on one single fiber.

Venk explained how Comcast has been able to launch coherent optics in the access domain and it’s been very successful in multiple divisions. “As pluggables become more pervasive, Comcast needs optics to be pluggable, with a good mixture of 100G, 400G, Bi-Di, 400ZR+ and 0dBm pluggable modules,” he said. “Performance, power dissipation, and software automation will continue to be very important, and routers will also need to address the speed and latency requirements.” According to Venk, Comcast is excited about pluggables and is thankful the industry has gotten them to the point where they enable the system to be simpler and more reliable.

Colt Sees 69% Capex Savings and 2X Reduction in Rack Space and Power Consumption
According to Bart Janssens, Senior Specialist Packet Network Architect at Colt Technology Services, 400G pluggables have become a vital piece of Colt’s next-generation packet networks. The company is a business-only infrastructure provider and when they look at their customer requirements, the main trend they see is the need to consume traditional cloud services on demand without limitations on the bandwidth they are consuming between end points.

Figure 6: Colt’s business customers want traditional cloud services on demand without limitations on the bandwidth

To meet these needs for performance and flexibility, Colt moved the traditional Provider/Provider Edge (P/PE) to the edge and then looked for the right technology to put at the center of its core. The solution they chose was Cisco’s Silicon One 8201, which gave them many QSFP-DD ports for 400G coherent pluggables. That allowed Colt to use a fraction of the rack space and power consumption at a much lower cost to build 35.4X more capacity per 1RU. This resulted in a core network using IPoDWDM 400G ZR+ between core routers. Colt then added the same layer in the metro, allowing them to aggregate 100G and 400G to the key data centers using 400G ER1/ZR (Acacia’s Bright 400ZR+)/LR4 DCI. And this year, they expect to extend this concept further to access routers moving to 400G.

According to Bart, 400G pluggables are driving growth in the future expansion they are doing, and he detailed some real-world use cases in Europe using LR, LR4 and ZR+. Colt has been able to improve their core transport costs by 69 percent capex, while at the same time helping the environment by removing rack space and power consumption by double digits. As Bart said in his closing remarks “What is really amazing is the transition of capex spending.  While in the past, the initial spend was on expensive routers, it’s the opposite today. We can just plug in more pluggables and scale our network to meet the never-ending customer growth.”

Watch the replay
Click here to register for the webinar which will give you access to the replay. You can read more about Acacia’s coherent pluggable portfolio here.  If you have any follow-up questions for any of the panelists, please feel free to reach out to us via this contact form.

The 400G OpenZR+ MSA expanded 400ZR reaches far beyond 120km by utilizing higher-gain forward error-correction coding (FEC) and increased compensation for chromatic and polarization mode dispersion. This enabled the use of 400G pluggables not only in hyperscale environments, but also in metro/regional service provider network environments. Service providers have thus been focusing on these “plus” versions of 400G modules for their network needs.

Brightening ROADM Networks
The latest expansion of 400G pluggable applications is being enabled by QSFP-DD form-factor modules, such as Acacia’s Bright 400ZR+ QSFP-DD, which have an optical transmitter power at least ten times greater than 400ZR. The higher transmitter power expands the applications that can be addressed by 400G coherent pluggable modules to include brownfield and greenfield metro/regional networks with reconfigurable optical add-drop multiplexer (ROADM) nodes, shown in Figure 1.

Figure 1.  Recently introduced Bright 400ZR+ QSFP-DD modules expand applications of 400G coherent pluggables to brownfield and greenfield metro/regional networks with ROADM nodes.

ROADMs enable the ability to selectively add/drop wavelengths to/from the network, avoiding optical-electrical-optical (OEO) conversions on channels passing through the ROADM node. Enabled by wavelength selective switch (WSS) technology, ROADM-based architectures can provide operational advantages compared to fixed optical add/drop solutions that required manual intervention for reconfiguration.

These network elements operate in tandem with terminal DWDM equipment and amplified single-span or multi-span line systems. To ensure optimal aggregate optical SNR performance, a certain level of transmit optical power and uniformity is required across the entire DWDM wavelength band. Having a 400G coherent pluggable QSFP-DD solution with high transmit optical power would enable 400G router-based optics to be deployed in a ROADM network architecture with existing wavelength traffic.

Bright Applications
Figure 2 illustrates two general examples of how Bright 400ZR+ QSFP-DD modules can be used in ROADM networks for sites with or without existing DWDM transponder terminal equipment.

(a)

(b)

Figure 2. 400G QSFP-DD pluggables with high transmit optical power can be used at a network node in new deployments (a) or with (b) existing DWDM transport/transponder terminal equipment.

IP-over-DWDM over ROADM Infrastructure
While point-to-point IP-over-DWDM architectures can be fully supported using 400ZR or OpenZR+ modules, there may be instances in which IP-over-DWDM traffic may need to traverse over a legacy ROADM infrastructure (Figure 2a), perhaps as an overlay with existing sites populated with DWDM transport terminal equipment (Figure 2b). Figure 2b also illustrates an alien-wavelength example where a router-port wavelength is inserted into a line system of a different vendor.

While there are network designs that support the use of -10dBm 400ZR+ modules over a ROADM network, it becomes a challenge when the DWDM transmission from these modules are adjacent to multiple legacy higher optical power channels (Figure 3a) resulting in relatively lower received optical power and OSNR. Legacy transponder terminal equipment typically have a per-channel ingress optical power in the 0dBm range. One solution is to add an external optical amplifier per module to boost the optical transmit power to the 0dBm level into the line system ingress.

By taking advantage of highly integrated silicon photonics design and packaging technology, such as Acacia’s 3D Siliconization, it is possible to eliminate the need for an external amplifier by incorporating the optical amplification into the compact QSFP-DD form factor module. Utilizing a 400G coherent pluggable with a higher optical transmitter power of at least 0dBm ensures sufficient optical power, relative to other DWDM wavelengths, to traverse through legacy ROADM nodes, as shown in Figure 3b.
(a)
(b)

Figure 3.  (a) A standard 400ZR/ZR+ module with transmitter output power of -10dBm co-exists with legacy higher power channels, subject to lower received optical power and OSNR; (b) a Bright 400ZR+ wavelength ensures channel power uniformity in ROADM/line-system ingress when combined with other line-system traffic.

Transmitting in High Fidelity
Many ROADM architectures utilize colorless multiplexing. This type of ROADM has a passive optical combiner element (Colorless MUX in Figure 4) that takes individual fiber inputs from different transmission wavelengths and combines them together into a single fiber without any optical filtering, hence the name colorless. In wavelength-agile network designs, external control of the tunable wavelengths avoids any contention issues. To minimize wavelength crosstalk/noise through colorless ROADMs, the transmitter OSNR of each ingress wavelength needs to be maximized. One way to achieve this is to attenuate the laser amplified spontaneous emission (ASE) noise using a band-pass optical filter to minimize optical crosstalk/noise into nearby channels. And to accommodate wavelength-agile networks, a tunable optical filter (TOF) is utilized.

Figure 4.   Illustration highlighting the benefits of a TOF inside a coherent module with internal optical amplification when multiple channels pass through a colorless multiplexer; comparison between (a) modules without TOF vs. (b) modules with TOF.

Figure 4 illustrates how multiple wavelengths are combined using a colorless MUX. In figure 4a, the noise from multiple modules without a TOF impacts nearby transmission channels through a colorless MUX. By using a TOF, not only does is transmit OSNR improved, but also the noise affecting adjacent channels is minimized. The Figure 4 inset illustrates how a TOF suppresses noise resulting in an optimal situation of a module wavelength insertion surrounded by legacy wavelength transmissions, shown in Figure 4b.

Higher Density DWDM Footprint
For network operators continuing to leverage an optical transport layer, the higher optical power QSFP-DD modules enable a higher density design for DWDM transponder terminal equipment. While high transmit optical power has been available in the CFP2 form factor for 400G, advanced integration and design has resulted in this capability in the smaller QSFP-DD housing.

The Acacia Bright Solution
Acacia recently introduced its Bright 400ZR+ coherent pluggable QSFP-DD module that transmits at least +1dBm of optical power to expand 400G coherent pluggable applications with brownfield and greenfield ROADM network architectures. This module leverages 3D siliconization to provide a highly integrated design enabling the silicon photonics integrated circuit (including TOF), coherent DSP, high-speed components, and optical amplifier to fit entirely into a compact QSFP-DD pluggable form-factor module. In addition to supporting interoperable OpenZR+ and Open ROADM modes, the Bright 400ZR+ QSFP-DD module can aggregate 4x100GbE client traffic and also utilize FlexO mapping for OTN transport applications.

Bright 400ZR+ Expands Applications for 400G Pluggables
High transmit power 400G pluggables, such as Acacia’s Bright 400ZR+ module, surpass the market applications served by 400ZR module by enabling an optical transmit power that is at least ten times greater (i.e., brighter). This is another significant milestone because it enables service providers and hyperscalers to take advantage of 400G pluggables in brownfield and greenfield ROADM based optical network architectures.

Additional Resources:

• Bright 400ZR+ coherent pluggable QSFP-DD module Product Page
• Arelion completes first multi-vendor, multi-layer field trial using Acacia Bright 400ZR+ modules and Cisco Routers

Acacia is excited to be participating once again in person!  We expect a number of hot topics to be front and center at the show – from the path to coherent lite, interoperable 400ZR/ZR+ pluggables ramping, and of course high-performance multi-haul solutions.

Coherent Lite

Over the last year, the industry has been abuzz around a new effort called “coherent lite,” which is a simpler implementation of coherent transmission that is designed for use in short reach campus and intra-DC applications. It essentially removes the features required for traditional transport DWDM applications.

Coherent lite pluggables can provide a competitive cost structure at 800G and beyond, utilizing fewer lasers, while meeting campus and intra-DC requirements. This solution can be a candidate for applications typically addressed by IM-DD solutions. We believe this will be a hot topic at the show.

The Rise of Standardized 400G Pluggables

The 400G coherent pluggable market is one of the most important developments in optical networking today. According to Cignal AI’s 4Q21 Transport Applications Report, shipments of 400ZR/ZR+ modules are expected to triple in 2022 as cloud operators such as Microsoft, Amazon, and Google are joined by traditional network operators such as AT&T, Windstream, and COLT rolling out high volume deployments.  Similarly, LightCounting’s Market Forecast from April 2022 estimates that the opportunity for pluggables based on 400ZR and 800ZR technology will surpass $2.8 billion by 2027.

Clearly, interoperable standards have played a key role in the rapid growth of pluggables. Standardization helps carriers by providing simplicity, interoperability and volume-driven cost. This has helped increase demand. The aggressive ramp of these products has been faster than any previous coherent technology generation. Several OIF members including Acacia are set to showcase multivendor interoperability for critical networking technologies at ECOC 2022.

OIF’s 400ZR project is proving successful in facilitating new and simplified architectures for high bandwidth inter-data center interconnects and promoting interoperability among coherent optical module manufacturers including Acacia’s 400ZR QSFP-DD. This 400ZR interop demo shows a full implementation across an 80km DWDM ecosystem using multiple form-factor pluggable modules, 400GbE routers, a 75 GHz C-band open line system, and test equipment solutions from multiple vendors. The demo provides evidence of widescale 400ZR deployment readiness based on a broad ecosystem of interoperable solutions.

Acacia’s newest entrant to the pluggable module category is the high transmit power 400G pluggable, which we are calling our “Bright” module.  We recently introduced the Bright 400ZR+ QSFP-DD pluggable coherent optical module with high optical performance designed for seamless deployment in ROADM line systems. These modules are designed to expand the applications for this technology by addressing a variety of ROADM architectures such as those with colorless multiplexing. With greater than +1 dBm transmit optical power and high transmit OSNR, Acacia’s Bright 400ZR+ gives network operators more flexibility to address a range of brownfield and greenfield applications utilizing the high-density QSFP-DD form factor.

High-Performance Multi-Haul Solutions

While pluggables are becoming extremely popular for router-based solutions in DCI, metro and some long-haul applications, transponder-based solutions are still required for long-haul, ultra-long haul and subsea. Transponders that include multi-haul high-performance modules can help network operators maximize their fiber investment, reduce power, simplify operations, and decrease costs.

The industry has shifted its focus to increasing the baud rate per carrier, while also introducing performance-improving innovations, to enable end-users to achieve cost-efficiencies as bandwidth demand continues to grow. As an example, newly introduced Class 3 120+Gbaud solutions based on silicon photonics offer a path to cost-effectively double capacity over a single carrier compared to earlier implementations.

Acacia’s performance optimized multi-haul coherent solutions have proven to be extremely effective at helping service providers meet these challenges.  Earlier this year, Acacia announced it had shipped more than 100,000 ports of its Pico DSP which powers the company’s highly successful AC1200 1.2TB module.

Building on this success, Acacia introduced its Coherent Interconnect Module 8 (CIM8), which is based on the company’s newest DSP technology, the 8^th generation Jannu 5nm DSP, and includes second generation 3D Shaping and continuous baud rate adjustment of up to 140Gbaud.  This new module achieves several industry firsts:

• The first single-carrier 1.2TB multi-haul pluggable module
• The first coherent module to support 140Gbaud
• The first 5nm multi-haul DSP

Acacia successfully demonstrated 140Gbaud performance with our high-performance silicon photonics at this year’s OFC 2022.

Speaking Sessions

To hear more about the topics discussed in this article, don’t miss our speaking sessions.

• Workshop: Adaptive everything! Do optical networks really need more flexibility?
  • Presentation title: 400ZR and OpenZR+: Enabling New Network Architecture Optimization
  • Speaker: Lorenzo Ghioni
  • Date/time:  Sunday September 18^that 9:15-9:25 am
• Market Focus Panel: Modules/Sub-Systems/Connectors/Line-Cards
  • Presentation title: Next Generation Coherent Interfaces: Standardized Pluggable vs Proprietary Multi-haul
  • Speaker: Tom Williams
  • Date/time: Tuesday September 20^that 10:00-10:25 am

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Network operators need to efficiently scale their networks to keep up with growing user bandwidth demands.  To meet this need, it is going to be increasingly important to develop next-generation solutions based on scalable technologies that are aligned with industry trends.

Trends Driving Coherent Optical Development

Coherent Moving to Shorter Reaches
As the industry moves to higher data rates, coherent is being adopted in shorter reach interfaces, which is increasing the share of coherent ports that are deployed in pluggable form factors. For example, the 400ZR specification targeted 80-120km reaches, and subsequently the OIF is now working on a project to define an 800LR that targets 10km and below. As this trend continues, it is likely that we’ll also see coherent move into the data center in future generations. These shorter reach interfaces tend to be higher volume than traditional transport applications, and as we look at this transition, it becomes more important to have interoperability and pluggable form factors that can plug directly into router interfaces.

Standardization is Key
The industry has been steadily moving to more standardization. 400G was a significant step forward and today we have a variety of standardized interfaces including 400ZR/ZR+ and Open ROADM – all of which are growing. These standardized interfaces are displacing both proprietary solutions in more traditional transport applications as well as direct detect solutions in shorter reach interfaces. Over time, most optical industry analysts agree that these standardized pluggable interfaces are expected to contribute a larger and larger portion of all the coherent ports in the industry.  Multi-haul solutions that address multiple applications will still be needed, but it will be important to align these multi-haul investments with standards.

Approaching the Shannon Limit
From a development perspective, incremental improvements in spectral efficiency are being made as we approach the Shannon Limit, but we need to find ways to grow network bandwidth more efficiently over time. In the past, we were able to scale the amount of data being transmitted over a single set of optics, while also increasing capacity on the fiber. Today, we are scaling as we increase baud rate, but the amount of data on the fiber is growing more incrementally. This is changing the way we develop products for the future and increasing baud rate cost-effectively is critical moving forward.

These three trends point to high-volume standardized solutions having a greater influence on next generation industry investment.

Coherent Technology Classifications

The below figure illustrates how coherent technology has evolved in response to growing bandwidth demands. Different baud rate classes are grouped based on technological capabilities, industry standardization (such as OIF, IEEE, Open ROADM, OpenZR+ MSA, CableLabs, ITU, IEEE) and common industry investments. Throughout this evolution, it has been critical that each successive class support similar reaches to the previous class.

Baud rate has doubled for each coherent technology class.

Class 1
There was a long period during the early days of coherent technology development with multiple investment nodes. At 30-34 Gbaud, there were 100G and 200G products and the industry made a significant investment at this stage. In this generation, there was widespread standardization of components such as modulators and receivers. However, standardized optical interfaces sacrificed significant performance compared to proprietary implementations, so they were not widely adopted.

Class 2
This is where the industry is today, and it is during this stage that standardized optical interfaces are being widely deployed for the first time. The first Class 2 products were proprietary interfaces supporting multi-haul applications in embedded module form factors. Later, 400G faceplate pluggables, driven by standardization efforts that drove heavy investments into products centered around 16QAM, 60+Gbaud per 75GHz channel transmission were introduced with strong industry adoption. When we migrated to Class 2, we doubled the baud rate and enabled an increase in the data rate.

Class 3
These products once again represent a doubling of baud rate compared to the class before it, with products migrating to 120-136 Gbaud. This approach of doubling baud rate is utilized in standards because it allows for this doubling of data rate using the same modulation format as the previous class. 4 bits/symbol was chosen for 400G standards because it supports a wide range of applications. When scaling from 400G to 800G, doubling the baud rate is the logical path forward.

Class 4
These products will continue the trend we saw in the earlier classes where the model is to increase baud rate but take additional steps to cover all applications. Like earlier trends, we expect the baud rate to also double from Class 3 to Class 4 products, while utilizing the same modulation order.

“These classifications basically mirror industry investment cycles, which is absolutely the right way to align coherent technology development around,” said Alan Weckel, Founder and Technology Analyst at 650 Group. “At the end of the day, operators need solutions to be cost effective and the best way to do that is to leverage the investment across all the various applications and benefit from higher volume production and scale. Increasingly coherent ports are moving to pluggable form factors and as we approach the Shannon Limit, further improvement in cost will come from going to higher baud rates, but in cost effective way.”

Acacia’s Class 3 Solution
Acacia’s recently announced Coherent Interconnect Module 8 (CIM 8)  is a Class 3 solution that can address transmission of multiple 400GbE client interfaces over virtually any network application, delivering 1.2T per carrier capacity for high-capacity DCI interfaces and 800G per carrier capacity over most optical links using 4 bits/symbol (~16QAM) modulation. This product supports 150GHz channels with double the capacity per carrier and longer reach than that of the previous class, providing a simple, scalable path that is compatible with the previous network architecture generation.

Acacia’s CIM 8 is the industry’s first 1.2 faceplate pluggable coherent module, powered by Acacia’s Jannu 5nm CMOS digital signal processor (DSP) ASIC. This solution delivers industry-leading performance with single carrier 1.2T operation and combines the Jannu DSP with 3D Siliconization packaging technology which includes the silicon photonics integrated circuit (SiPh PIC), high-speed modulator driver and transimpedance amplifier (TIA) in a single opto-electronic package. With 3D Siliconization, the high-speed RF interfaces are tightly coupled together, resulting in improved signal integrity for high baud rate signals. The high-density packaging as well as an advanced high-speed modulator design that enables the 140Gbaud performance as explained in this white paper.

The Future of Coherent Development

As the coherent technology classifications chart highlights above, the industry has undergone several large investment phases.  This has been good for the industry because it allowed vendors to have a significant ROI, worked well with network operator upgrade cycles, and avoided many small iterative steps in between. However, moving forward it is going to be important to align with these industry investments. As a result, we need to think about how to develop solutions that scale to high volume in a power-efficient and cost-effective way. Silicon photonic based coherent interfaces have proven to be successful in meeting these challenges generation after generation and we believe this technology can continue to help effectively meet bandwidth demands of the future.

Here are a few notable accomplishments from the past year.

The Rise of 400G Pluggables
Bandwidth demands have continued to grow, putting pressure on cloud providers to increase the data center interconnects (DCI) that link their facilities around the globe. This has helped to drive the emergence of new architectures that could support coherent transport in the same form factors as client optics, to satisfy those demands in a cost-effective and operationally efficient way. 400G pluggables were designed to be plugged directly into switches and routers, offering the same density for both coherent DWDM and client optics in the same chassis.

Utilizing our 3D siliconization technology, Acacia introduced a family of 400G pluggable solutions featuring an expansive list of interoperability modes (400ZR, OpenZR+, Open ROADM MSA and CableLabs Coherent Optics Physical Layer Specification). These solutions were designed to enable DCI and service provider network operators to address increasing bandwidth demand through a simplified network architecture, helping to reduce both capital and operational expenditures.

Modules based on multi-sourced 400ZR DSPs are now being validated for readiness in DCI applications and network operators are evaluating OpenZR+ solutions with enhanced functionality.  For example, Acacia and Inphi recently demonstrated interoperability of 400ZR over 120km. In addition, Acacia and NTT Electronics announced successful interoperability testing of 400ZR and OpenZR+. At Acacia, we believe we will see system vendors and network operators announcing trials in the near future.

Coherent Moves to Edge and Access
The benefits of coherent have already been demonstrated in the metro, long-haul and submarine markets, and with the coming of 5G and edge computing, the time is right for coherent optics to take the next step and migrate to edge and access networks. We believe this market can benefit from the scalability, operational simplicity and improved total cost of ownership that coherent has to offer.

To address the wide variety of requirements in the edge and access market, Acacia recently announced a portfolio of products, including a coherent bi-directional pluggable optical module for cable and 5G wireless X-haul applications, a 100G coherent point-to-point edge and access solution for 5G Wireless X-haul and Enterprise Services, and a 100G coherent DWDM module for cable/fiber deep and 5G wireless X-haul applications.

Multi-Haul Coherent Solutions Take Off
With bandwidth demands continuing to rise, network operators have been looking for solutions that improve efficiency and maximize capacity utilizing while reducing network cost.  Multi-haul solutions have emerged to meet the needs of many markets including cloud, metro, long-haul and submarine network applications by providing the high performance and flexibility features required to address meet these demanding applications.

Acacia’s AC1200 product family offers customers a multi-haul solution designed to cost-effectively improve network utilization in a wide range of network architectures. Supporting transmission speeds of up to 1.2 Tbps, the AC1200 utilizes Acacia’s 3D shaping technology designed to optimize fiber capacity and reach by filling gaps in margin and spectrum. In addition to its higher capacity and density, Acacia’s AC1200 product family, when embedded inside a number of our network equipment manufacturer partners’ products, provides features designed to enable network operators to improve efficiency while reducing network costs.

Here are a few examples.

Long-haul Terrestrial Applications
ADVA announced that the FSP3000 TeraFlex broke multiple industry records in live network trial. ADVA also announced that FUNET trialed ADVA FSP 3000 TeraFlex to dramatically expand network capacity and Serverius, one of the Netherlands’ largest data center service suppliers, is leveraging its FSP 3000 TeraFlex terminal to massively increase the capacity of its deployed infrastructure.

Submarine Applications
Cisco is making waves in the subsea market having demonstrated the benefits of the NCS 1004 over a subsea cable in production achieving record results. Cisco and Superloop announced two deployments of up to 400G for 4600km on the INDIGO West cable from Singapore to Australia, and the INDIGO Central cable from Perth to Sydney, featuring a two-fibre pair ‘open cable’ design with new spectrum sharing technology.

Oh What a Year – But the Show Must Go On
As NGON & DCI World and ECOC go virtual this year, I am looking forward to presenting in the following two panels. I hope to see many of you online and from all of us at Acacia…stay safe and healthy and have a great rest of the year.

• NGON & DCI World on Dec 1 at 9:00 am ET: “Next Generation Optics for Increased Capacity”
• ECOC Market Focus on Dec 7 at 17:00 CET: “A Path to Next Generation Coherent”

Contact us if you would like to schedule a meeting with myself or one of my colleagues.

These examples illustrate how the interconnects that make up the data center network infrastructure play an important role in a hyperscaler’s network evolution. Recently introduced 400G switches and pluggable optical modules are new tools that enable hyperscalers to transform how data center networks are being architected, with an anticipated impact of comparable magnitude to when 10G and later 100G solutions were introduced. These 400G solutions are designed to enable network operators to address increasing bandwidth demand through a simplified network architecture, targeting the reduction of both capex and opex.

Figure 1: Data center network operators can scale up DCI bandwidth with 400G 400ZR and OpenZR+ solutions.

High-capacity switch and router platforms with 400 gigabit Ethernet ports are transforming hyperscale data center networks by enabling higher switching capacity (using 12.8/25.6Tbps ASICs). Recently introduced 400ZR and OpenZR+ QSFP-DD or OSFP form-factor coherent optical modules are designed to plug into these ports. A network operator with a sizeable percentage of 400G optical Ethernet connections between switches/routers less than 120km links in their edge network can utilize 400ZR modules, while OpenZR+ modules can be used for regional links greater than 120km. Network operators can plug these modules into ports alongside shorter reach client optics modules.

New deployment opportunities can leverage the capability of having both transport (400ZR/OpenZR+) and client optics plugged in the same switch/router to support an IP-over-DWDM (IPoDWDM) network architecture where switching is performed at the IP layer rather than the optical transport layer. An IPoDWDM network reduces cost per bit as well as operational overhead since a separate transport platform layer is not required, and network management can be consolidated. Eliminating the separate transport layer can also result in solution density improvements and reduced power consumption of approximately 25%.

Figure 2: Two architectures to support 400G IP/Ethernet traffic over an optical infrastructure are (1) traditional separation of the IP/Ethernet layer from the DWDM optical transport layer (top) or (2) IP-over-DWDM using 400ZR or OpenZR+ modules which plug directly into the switch/routers (bottom).

Transport optics in pluggable client form factors plugged directly into routers/switches is not an entirely new concept. What makes 400ZR/OpenZR+ different than earlier 100G solutions (besides the 4x capacity increase) is longer reach capability via coherent transmission, and wavelength tunability which provides operational benefits of deployment ease and spares reduction.

Legacy architectures that use a separate DWDM optical transport platform with a modular design (via line-cards or sleds) can be designed with an upgrade path to support these new 400G interfaces. Ethernet-centric ports can then be economically optimized using pluggable 400ZR or OpenZR+ modules.

Figure 3: Acacia 400G pluggable coherent optical modules supporting 400ZR and OpenZR+ (QSFP-DD on left, OSFP on right).

Some hyperscalers may find it necessary to maintain a separate IP layer from the optical transport layer, especially to support legacy infrastructure. Others may want to reduce the amount of equipment they have to manage using IPoDWDM if they do not require supporting legacy infrastructure, especially given scalability concerns.

To enable the wide adoption of 400ZR, these modules should be designed for volume production. However, packaging optics into the QSFP-DD/OSFP form factors is challenging. Complying with these compact mechanical designs while meeting specifications for performance, power consumption and cost focuses on three important areas: the DSP, optical/electrical component consolidation, and high-density packaging.

Acacia’s 3D Siliconization follows the example of the electronics world, applying integration and co-packaging techniques such as 3D stacking. Advantages of 3D Siliconization include the reduction of electrical inter-connects while preserving robust signal integrity, as well as using silicon photonics to leverage electronics semiconductor fabrication process suitable for volume production and high yields.

After much anticipation, the curtain has been drawn open. Entering onto the stage…400G pluggable coherent transceiver modules! The recent introduction of 400G solutions, such as Acacia’s 400ZR and OpenZR+ pluggable coherent optical modules, were designed to bring about another transformative implementation of optical networking solutions for data center interconnects.

Stay tuned for our next 400G blog, when we will go into more details on the applications driving OpenZR+ requirement.

To address the need for higher DCI bandwidth requirements to meet this growing demand, the optical networking industry began working on a solution known as the 400ZR implementation agreement, with a goal to combine optical line-side fiber capacity with the benefits of client-side solutions.

Spearheaded by the Optical Internetworking Forum (OIF), 400ZR aims to deliver accessible 400 gigabit-per-second (Gbps) Ethernet links for edge DCI applications. The 400ZR implementation agreement addresses edge-DCI applications with link distances targeting 80 km to 120 km and can be implemented in pluggable 400Gbps optical transceiver module form-factors used for client optics.

The primary 400ZR use case is to apply the technology to DCI edge networks.

The 400ZR standard leverages the reach and capacity benefits of coherent optical technology, while challenging the industry to implement the technology in compact pluggable module form-factors such as QSFP-DD and OSFP.

We recently published a market backgrounder that reviews the industry drivers behind the development of 400ZR, the key benefits of the technology, and a product-development roadmap for bringing 400ZR transceivers to market. It also provides a few predictions on how the technology could potentially change the industry. Check it out to learn more and let us know what your predictions are.

Read the White Paper