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.

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.