To date, multiple system vendors have converged around Class 3-based solutions (Figure 1), recently announcing their next generation offerings. This industry convergence creates the benefit of economies of scale and broad industry investments into the technology used in this baud rate class, the same class being used for 800G MSA pluggable solutions.

Figure 1.  Acacia and other coherent vendors have announced Class 3 Terabit Era solutions.

Advancements Resulting in 65% Power-per-Bit Savings Over Current Competing Solutions
Doubling the baud rate from Class 2 to Class 3 in silicon was a significant engineering achievement, combining design advancements in high-speed Radio Frequency (RF) and Analog to Digital Converter (ADC) and Digital to Analog Converter (DAC) components plus well-designed co-packaging integration of silicon and silicon photonic (SiPh) components. These achievements led to Acacia’s successful 140Gbaud in-house capability that is being leveraged in the commercially available CIM 8 solution.

With high-volume shipments of multiple coherent Class 2 module products utilizing Acacia’s 3D Siliconization, this proven co-packaging integration solution provided the foundation for extending this capability to Class 3 140Gbaud implementation utilized in the CIM 8 (Figure 2). 3D Siliconization maximizes signal integrity by co-packaging all high-speed components including the coherent Digital Signal Processor (DSP) application-specific integrated circuit (ASIC), transmitter and receiver silicon photonics, and 3D stacked RF components into a single device that is manufactured in a standard electronics packaging house. Silicon technology has demonstrated cost and power advantages over alternative technologies, making it the material system of choice for these higher baud rates. These advancements enabling a doubling of the baud rate have led to a 65% power-per-bit savings of CIM 8 over current competing solutions that utilize alternative optical material systems. In addition, the size and power savings of this latest generation enabled the ability to house this 1.2T 140Gbaud solution in a pluggable form-factor.

Figure 2.  An example of 3D Siliconization used in the CIM 8 module, resulting in a volume electronics manufacturable high-speed single device larger than a quarter.

2^nd Generation 3D Shaping Advances Coherent Performance
The CIM 8 is powered by Jannu, Acacia’s 8^th generation coherent DSP ASIC. The design greatly expands on the success of the Pico DSP ASIC predecessor used in the widely deployed performance-optimized Class 2 AC1200 module (Figure 1). The AC1200 was the first module to introduce 3D Shaping, which provided finely tunable Adaptive Baud Rate up to 70Gbaud as well as finely tunable modulation up to 6 bits/symbol. The AC1200 had achieved record breaking spectral efficiency at the time of its introduction, as evidenced by a subsea trial over the MAREA submarine cable connecting Virginia Beach, Virginia to the city of Bilbao in Spain. Finely tunable baud rate helps maximize spectral efficiency in any given passband channel, converting excess margin into additional capacity/reach, and avoids wasted bandwidth due to network fragmentation.

Figure 3.  A popular feature is the fine-tunability of baud rate introduced by Acacia with the Class 2 AC1200; CIM 8 incorporates the same Adaptive Baud feature (as part of 2^nd Generation 3D Shaping) for Class 3 baud rate tunability.

The 5nm Jannu DSP ASIC in CIM 8 intelligently optimizes optical transmission using 2^nd Generation 3D Shaping with an increased Adaptive Baud Rate tunable range up to 140Gbaud, as well as finely tunable modulation up to 6 bits/symbol using enhanced Probabilistic Constellation Shaping (PCS). With 2^nd Generation 3D Shaping, the CIM 8 module can achieve a 20% improvement in spectral efficiency.

Terabit Era Solutions Provide Full Network Coverage
Class 3 technology not only ushers in the terabit era, but also enables full multi-haul network coverage as the high baud rate capabilities transport nx400GbE client traffic across a service provider’s entire network. Full network coverage is not only enabled by adjustment of the modulation, but also implies the capability to optimize for various network conditions which include overcoming transmission impairments.

Figure 4. CIM 8 1.2T, 1T, 800G, and 400G transmission constellations operating at Class 3 baud rates providing wide network coverage addressing multiple applications.

CIM 8 offers significant power-per-bit reductions as well as cost efficiencies for various optical network transport applications.

DCI/Metro Reaches
For transporting 3x400GbE or 12x100GbE client traffic with metro reaches in a single carrier, the CIM 8 is tuned to ~6 bits/symbol (equivalent to 64QAM, example constellation on left). Data center interconnect (DCI) applications would take advantage of this high-capacity 1.2T transport capability to tie data center locations together. This amounts to 38.4T per C-band fiber capacity.

Long-Haul Reaches

For transporting 2x400GbE with long-haul reaches, the CIM 8 is tuned to ~4 bits/symbol (equivalent to 16QAM, example constellation on the right). Wide 800G network coverage is achieved with the Class 3 140Gbaud capabilities enabling service providers to provide end-to-end 2x400GbE, 8x100GbE, or native 800GbE transport across their networks, covering essentially all terrestrial applications.

Ultra-Long-Haul/Subsea Reaches

And for ultra-long-haul/subsea reaches, the CIM 8 is tuned to ~2 bits/symbol (equivalent to QPSK, example constellation on the left). As with the previous scenarios, spectral efficiency with a wavelength channel is optimized by fine-tuning of the baud rate. These high spectrally efficient modes can carry mixed 100GbE and 400GbE traffic over the longest subsea routes in the world with lowest cost per bit. It’s worth noting that almost a decade ago, Acacia demonstrated SiPh capabilities for subsea coherent deployments. CIM 8 incorporates second generation non-linear equalization (NLEQ) capabilities to mitigate the non-linear effects of optical transmission especially for these ultra-long-haul/subsea links providing additional OSNR.

In all the above scenarios, the CIM 8 utilizes advanced power-efficient algorithms to compensate for chromatic and polarization dependent dispersion. In addition, the module accounts for coverage of aerial fiber network segments that require fast state-of-polarization (SOP) tracking and recovery due to lightning strikes. The SOP tracking speed of CIM 8 is double the speed of its predecessor. This fast SOP tracking feature can also be utilized for sensing applications.

Network Operators Achieve Record Breaking Field Trials with CIM 8
CIM 8 capabilities have already been put to the test as illustrated by multiple record breaking field trials across a wide range of applications. These include >5600km 400G transmission over a mobile carrier’s backbone network, 2200km 800G transmission over a research and education network, and >540km 1T transmission over a wholesale carrier’s network.

Acacia continues to demonstrate its technology leadership by leveraging mature knowledge in proven silicon-based coherent technology, producing the first shipping coherent solution to lead the industry into the Terabit Era with the 1.2T pluggable CIM 8 module. With the breakthrough capability of 140Gbaud transmission along with the advanced Jannu DSP ASIC using 2^nd Gen 3D Shaping and leveraging 3D Siliconization, network operators can support full network coverage for multi-haul applications, especially to support growing demands for nx400GbE and upcoming 800GbE traffic.

References:
Blog: Terabit Today: Maximize Network Coverage
Blog: How Industry Trends are Driving Coherent Technology Classifications
Blog Series: The Road Ahead for Next-Generation Multi-Haul Designs Part 1, Part 2, Part 3

As generational gains in spectral efficiency, size and power become less significant, increasing baud rate is proving to be effective at significantly decreasing power per bit.

Performance Matters for Verizon as They Plan to Use Both Embedded and Pluggable Optics
Glenn Wellbrock, Director Optical Transport Planning for Verizon, talked about pluggables versus performance optimized (a.k.a. embedded) coherent modules, and how it’s important to leverage the volume that the hyperscalers are using to drive lower cost and power consumption. Glenn commented that the performance of the pluggable modules they’ve tested has exceeded their expectations. While they still plan to use performance optimized optics, they also plan to take advantage of pluggables anywhere they can because of the benefits they can provide in lower cost and power consumption.

Embedded Optics Used Primarily in Ultra Long-Haul Routes Operating Above 400G
On the performance optimized side, Glenn explained how it’s all about getting high performance, which by default usually means higher cost and proprietary implementations. He then went on to describe a field trial that Verizon completed where they were running embedded optics at maximum data rate for metro distances. They tested the same system at lower speeds for a long-haul route from New York to Chicago, demonstrating the benefits of a multi-haul solution. This proved that they could run 400G pretty much anywhere in the country.  Glenn also shared that on their long-haul networks, 80% is at or below 1,500km and 600G should be sufficient.

Verizon Plans to Continue Using Performance Optimized Embedded Optics for Ultra Long Haul
In the future, Glenn believes that both performance optimized optics and pluggables will continue to go up in performance. Today, the majority of Verizon’s new Ultra Long Haul (ULH) routes in its network are operating above 400G with embedded optics. According to Glenn, even if the next generation of optics gave Verizon 800G anywhere in the country with great performance, they would still want to know if they could get up to a Terabit or even 1.2T.  “If that will work on a lot of Verizon paths in a ULH environment, that is where Verizon is going to gravitate towards and it’s looking like that is going to happen with embedded optics,” added Glenn.

Acacia Sees Trends Influencing How Coherent Interfaces Should Be Developed
Tom Williams, Acacia’s Senior Director of Marketing, highlighted some of the key trends in the industry, starting with coherent moving to shorter reaches. This migration drives higher volumes as well as a need for more standardization because operators want the operational efficiency of interoperability and standards.

400ZR/ZR+ is exceeding expectations and is the fastest coherent product ramp ever displacing both proprietary coherent and direct detect solutions.

Tom recapped how 400ZR/ZR+ has exceeded expectations by being the fastest growing coherent ramp of all time. “We are seeing the core applications that drove the initial OIF 400ZR in the DCI use case and in many of those cases we saw MSA pluggables displacing performance optimized coherent and in others it replaced direct detect,” said Tom. “This has resulted in standardized pluggable optics taking up a higher portion of the coherent market.”

Tom also pointed out that during that same timeframe, the performance of embedded optics has scaled to the point where the industry is approaching the Shannon limit. As a result, component makers are now only seeing incremental improvements in spectral efficiency and operators are not getting significant improvement in capacity on the fiber. That has created a critical need to move to higher baud rates and higher data rates because they provide better economics and better power efficiency from optics. The most efficient way to do this is to develop high performance solutions that align with the investment that is already taking place in the shorter reaches in the pluggable space.

To illustrate the importance of taking the right steps with coherent development, Tom then described the path Acacia has taken. At each class, the company has developed both MSA pluggables and performance optimized solutions. Tom emphasized that, “The benefit that Acacia gets is that we make a big investment in each of these nodes, and we’ve been able to double the baud rate each time. We’ve seen the standards doing this and we’ve aligned our performance optimized solution with those standardized efforts.”  As an example, Acacia took the proven optics from the AC1200 operating at 70Gbaud and brought them into the company’s 400ZR/ZR+ products. Using the same platform allowed Acacia to then focus on advancing its packaging technology to take advantage of the efficiencies and have a scalable approach. And today, that same packaging technology is now feeding into the Coherent Interconnect Module (CIM) 8 module, which is enabling a pluggable performance optimized solution operating at 140Gbaud. It’s expected that the next generation will also have a doubling of the baud rates (as shown below) which would adhere to where the standards are expected to align.

Leveraging common development based on standards for both performance optimized, and pluggable solutions leads to higher data rates.

As Tom explained, the reason advancements in packaging have been so important is because the high-speed electrical interconnects are often the problem in the RF path when you start going to higher baud rates. By eliminating most of those interconnects, Acacia has been able to significantly extend the bandwidth of the RF chain and still get all the benefits of silicon and standards CMOS processes. Based on the Jannu DSP, the CIM 8 started shipping at the end of 2022 and has already been used in field trials with NYSERNet, China Mobile and Windstream Wholesale.

Nokia Looks to Lower Cost Per Bit with New Techniques
Serge Melle, Director Optical Product Marketing at Nokia, focused on what performance optimized solutions provide from a network applications standpoint. This started with a look at the trends that Nokia sees, and which are driving the key requirements for operators, which include bandwidth growth, faster internet speeds from IP routing platforms, and the need to lower network power consumption to achieve sustainability objectives.

As Serge stated, “This is really where this new generation of 5nm, 120Gbaud+ technology can address all of these things at the same time with the same technology evolution.” By being able to go to 1.2T wavelengths, operators can leverage the technology to achieve 2.4T in a single line card. That enables network operators to get much more scale in deployment of the bandwidth and reduce total cost of ownership, while also providing an effective means of transporting high speed services such as 400 Gigabit Ethernet and 800 Gigabit Ethernet. In addition, the performance improvement of this new generation of technology enables operators to triple the reach at 800G speeds – thereby going from several hundreds of kilometers to 2,000km distances at 800G per wavelengths.  Added Serge, “This is a very effective way to transport high-speed services across all network applications and can drive a significant reduction in the number of coherent optics needed in the network, which in turns leads to cost savings.  This technology can also provide significant network power savings because it can lower network power consumption by up to 60 percent.”

Like the prior speakers, Serge also stressed the importance of driving down the power per bit. “Every coherent generation has been able to achieve that and this latest generation of 1.2T technology continues the trend by leveraging 5nm silicon, silicon photonics and closer integration,” he said.

Finally, Serge shared how this latest generation of technology can be leveraged across a broad range of applications including metro DCI, long-haul and subsea networks.

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Supporting data rates up to 1.2 terabits per second (1.2Tbps), the CIM 8 is the first commercial single optical carrier coherent transceiver that breaks into the “Terabit Era.” It is powered by Jannu, Acacia’s 8^th generation digital signal processor (DSP) ASIC, which is based on 5nm CMOS and features the latest in Silicon Photonic technology.  This solution delivers industry-leading performance in a small faceplate pluggable module by combining the Jannu DSP with 3D Siliconization packaging technology. The CIM 8 supports multi-haul applications by using second-generation 3D Shaping technology and continuous baud rate adjustment up to 140Gbaud, enabling customers to scale their networks efficiently and cost-effectively.

“The ability to maximize transmission data rate across a wide range of multi-haul network applications is key for cost-effectively scaling networks,” said Bill Gartner, SVP / GM Optical Systems and Optics Group at Cisco.  “Not only does the CIM 8 deliver exceptional performance, but it also consumes less than half the power per bit of competing solutions, allowing us to support terabit transmission with a small pluggable module.”

“Shipping CIM 8 Terabit Era optical transceivers with 140Gbaud capability to customers and seeing them tested in carrier networks is very exciting,” said Mehrdad Givehchi, VP of Engineering for Acacia. “Delivering the highest channel capacity and longest reach with maximum fiber utilization, the CIM 8 transceiver enables a wide range of multi-haul network applications including DCI, metro, long-haul, and subsea.”

Benefits of Increased Baud Rates

Increasing baud rate is an efficient way to enable more cost-effective optical networks by reducing the number of optics needed to support a given transmission capacity. By doubling the baud rate between successive generations, CIM 8 supports twice the capacity per carrier over greater reaches than earlier generations such as our widely deployed AC1200 coherent module. Three 400GbE client interfaces can be transmitted over virtually any network application, delivering 1.2Tbps per carrier capacity for high-capacity DCI interfaces, 800G per carrier capacity over most optical links using 4 bits/symbol (~16QAM) modulation and 400G QPSK over ultra-long-haul and subsea distances.

Performance Optimizing Features Enabled by the Jannu DSP

A key feature of the Jannu DSP is Acacia’s second-generation 3D Shaping technology, which includes advanced Probabilistic Constellation Shaping, Adaptive Baud Rate, and enhanced transmission impairment compensation algorithms providing superior performance using a single carrier implementation. This technology gives service providers unprecedented transmission flexibility to match their network’s architecture, optimize fiber utilization, simplify deployment, and save on both CAPEX and OPEX.

The Jannu DSP provides customers with continuous baud rate adjustment up to 140Gbaud and continuous modulation to optimize utilization of available spectrum in point-to-point DWDM or cascaded ROADM paths. As a single carrier design, the Jannu DSP incorporates Acacia’s most advanced line-rate processing algorithms to efficiently overcome fiber transmission impairments across various fiber types and fiber cable installation conditions. These power-efficient algorithms are designed to compensate fiber non-linearity to achieve longer transmission distance, automatically compensate for very large chromatic dispersion over trans-Pacific submarine cables, tolerate older deployed fibers with high Polarization Mode Dispersion, as well as provide fast state-of-polarization tracking required for aerial fiber cables in stormy weather conditions.

Leverages Acacia’s 3D Siliconization

The CIM 8 continues Acacia’s history of technology leadership by delivering industry leading performance based on the same silicon photonics used in high-volume pluggable modules. 3D Siliconization, a key enabler for the industry leading 140Gbaud, uses highly scalable and reliable volume semiconductor manufacturing processes, leveraging 3D stacking technology to enable a single packaged device to include all the high speed electrical and opto-electronic functions necessary for coherent transceivers. This device decreases footprint by integrating the DSP, Photonic Integrated Circuit, modulator drivers, and Transimpedance Amplifiers, and is manufactured using standard CMOS packaging processes that offer improvements in reliability, cost, and volume scaling.

To learn more, visit the Coherent Interconnect Module 8 page or contact us.

Supporting Resources

Acacia Unveils Industry’s First Single Carrier 1.2T Multi-Haul Pluggable Module

How Industry Trends are Driving Coherent Technology Classifications

The Road Ahead for Next Generation Multi-Haul Designs (Part 1 of 3)

The Road Ahead for Next Generation Multi-Haul Designs (Part 2 of 3)

The Road Ahead for Next-Generation Multi-Haul Designs (Part 3 of 3)

100GBaud+ Silicon Photonics Solutions Drive Optical Network Evolution