FEC Archives - EFFECT Photonics

Insights

July 19, 2023

Towards a Zero Touch Coherent Network

Telecommunication service providers face a critical challenge: how to incorporate affordable and compact coherent pluggables…

Telecommunication service providers face a critical challenge: how to incorporate affordable and compact coherent pluggables into their networks while ensuring optimal performance and coverage across most network links.

Automation will be pivotal in achieving affordable and sustainable networks. Software defined networks (SDNs) facilitate network function virtualization (NFV), empowering operators to implement various functions for network management and orchestration. By incorporating an artificial intelligence (AI) layer for management and orchestration with the SDN/NFV framework, operators can unlock even greater benefits, as depicted in the diagram below.

carrier-network — Figure 1: Example of a carrier network with different applications (mobile, home, office) automated via SDN control and AI management.

Nevertheless, achieving a fully automated network requires interfacing with the physical layer of the network. This requires intelligent, coherent pluggables capable of adapting to diverse network requirements.

Zero Touch Networks and the Physical Layer

Telecom and datacom providers aiming to achieve market leadership must scale their operations while efficiently and dynamically allocating existing network resources. SDNs offer a pathway to accomplish this by decoupling switching hardware from software, thereby enabling the virtualization of network functions through a centralized controller unit. This centralized management and orchestration (MANO) layer can implement network functions that switches alone cannot handle, enabling intelligent and dynamic allocation of network resources. This enhanced flexibility and optimization yield improved network outcomes for operators.

Figure 2: Comparing a traditional network approach (left) with an SDN/NFC approach (right).

However, the forthcoming 5G networks will introduce a multitude of devices, software applications, and technologies. Managing these new devices and use cases necessitates self-managed, touchless automated networks. Realizing the full potential of network automation requires the flow of sensor and control data across all OSI model layers, including the physical layer.

As networks grow larger and more complex, MANO software necessitates greater degrees of freedom and adjustability. Next-generation MANO software must optimize both the physical and network layers to achieve the best network fit. Attaining this objective demands intelligent optical equipment and components that can be diagnosed and managed remotely from the MANO layer. This is where smart pluggable transceivers with reconfigurable DSPs come into play.

The Role of Forward Error Correction

Forward error correction (FEC) implemented by DSPs serves as a crucial component in coherent communication systems. FEC enhances the tolerance of coherent links to noise, enabling longer reach and higher capacity. Thanks to FEC, coherent links can handle bit error rates that are a million times higher than those of typical direct detect links. In simpler terms, FEC algorithms allow the DSP to enhance link performance without necessitating hardware changes. This enhancement can be compared to image processing algorithms improving the quality of images produced by phone cameras.

network link with FEC — Figure 3: Simplified diagram of a network link with forward error correction (FEC). The FEC encoder adds a series of redundant bits (called overhead) to the transmitted data stream. The receiver can use this overhead to check for errors without asking the transmitter to resend the data.

When coherent transmission technology emerged, all FEC algorithms were proprietary, guarded closely by equipment and component manufacturers due to their competitive advantage. Consequently, coherent transceivers from different vendors were incompatible, and network deployment required reliance on a single vendor.

However, as data center providers pushed for deeper disaggregation in communication networks, the need for interoperability in coherent transceivers became evident, leading to the standardization of FEC algorithms. The OIF 400ZR standard for data center interconnects adopted a public algorithm called concatenated FEC (CFEC). In contrast, some 400ZR+ MSA standards employ open FEC (oFEC), which provides greater reach at the expense of additional bandwidth and energy consumption. For the longest link lengths (500+ kilometers), proprietary FECs are still necessary for 400G transmission. Nevertheless, public FEC standards have achieved interoperability for a significant portion of the 400G transceiver market.

The Promise of the Smart Transceiver

The realization of a smart coherent pluggable capable of addressing various applications—data centers, carrier networks, SDNs—relies on an equally intelligent and adaptable DSP. The DSP must be reconfigurable through software to adapt to diverse network conditions and use cases.

For instance, a smart DSP could switch between different FEC algorithms to match network performance and use case requirements. Consider the scenario of upgrading a 650-kilometer-long metro link running at 100 Gbps with open FEC to achieve a capacity of 400 Gbps. Open FEC might struggle to deliver the required link performance. However, if the DSP can be reconfigured to employ a proprietary FEC standard, the transceiver would be capable of handling this upgraded link.

	400ZR	Open ZR+	Proprietary Long Haul
Target Application	Edge data center interconnect	Metro, Regional data center interconnect	Long-Haul Carrier
Target Reach @ 400G	120km	500km	1000 km
Form Factor	QSFP-DD/OSFP	QSFP-DD/OSFP	QSFP-DD/OSFP
FEC	CFEC	oFEC	Proprietary
Standards / MSA	OIF	OpenZR+ MSA	Proprietary

Table 1: Summary of different use cases and standards for a 400G pluggable transceiver.

Reconfigurable DSPs also prove beneficial in auto-configuring links to address specific network conditions, particularly in brownfield links. For example, if the link possesses high-quality fiber, the DSP could be reconfigured to transmit at a higher baud rate. Conversely, if the fiber quality is poor, the DSP could scale down the baud rate to mitigate bit errors. Furthermore, if the smart pluggable detects a relatively short fiber length, it could reduce laser transmitter power or DSP power consumption to conserve energy.

Takeaways

Smart coherent access pluggables would greatly simplify network upgrades. The DSP to match this pluggable should be able to use different error correction levels to handle different reach and future zero-touch network requirements.

The DSP can not only introduce software corrections but also effectuate optical hardware adjustments (output power, amplifier control) to adapt to different noise scenarios. Through these adaptations, the next generation of pluggable transceivers will proficiently handle the telecom carrier and data center use cases presented to them.

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Tags: 100G ZR, adaptable, AI, artificial intelligence, automation, Coherent pluggables, cost, data layer, DSPs, FEC, forward error correction, network layer, Network management and orchestration, network requirements, OPEX, physical layer, programmability, Proprietary, reach, reconfigurable, remote, SDNs, Service Providers, smart, Smart pluggable transceivers, software defined, Software-Defined Networks, standardized, standards, telecommunication, versatile, virtualization

Insights

March 22, 2023

Transceivers in the Age of AI

Artificial intelligence (AI) will have a significant role in making optical networks more scalable, affordable,…

Artificial intelligence (AI) will have a significant role in making optical networks more scalable, affordable, and sustainable. It can gather information from devices across the optical network to identify patterns and make decisions independently without human input. By synergizing with other technologies, such as network function virtualization (NFV), AI can become a centralized management and orchestration network layer. Such a setup can fully automate network provisioning, diagnostics, and management, as shown in the diagram below.

Figure 1: Example of a carrier network with different applications (mobile, home, office) automated via NFV control and AI management.

However, artificial intelligence and machine learning algorithms are data-hungry. To work optimally, they need information from all network layers and ever-faster data centers to process it quickly. Pluggable optical transceivers thus need to become smarter, relaying more information back to the AI central unit, and faster, enabling increased AI processing.

Faster Transceivers for the Age of AI

Optical transceivers are crucial in developing better AI systems by facilitating the rapid, reliable data transmission these systems need to do their jobs. High-speed, high-bandwidth connections are essential to interconnect data centers and supercomputers that host AI systems and allow them to analyze a massive volume of data.

In addition, optical transceivers are essential for facilitating the development of artificial intelligence-based edge computing, which entails relocating compute resources to the network’s periphery. This is essential for facilitating the quick processing of data from Internet-of-Things (IoT) devices like sensors and cameras, which helps minimize latency and increase reaction times.

400 Gbps links are becoming the standard across data center interconnects, but providers are already considering the next steps. LightCounting forecasts significant growth in the shipments of dense-wavelength division multiplexing (DWDM) ports with data rates of 600G, 800G, and beyond in the next five years. We discuss these solutions in greater detail in our article about the roadmap to 800G and beyond.

Figure 2: Shipments of high-speed DWDM ports by data rate (historical data and forecast). Source: LightCounting Optical Communications Market Forecast, April 2022.

Coherent Modules Need to Provide More Telemetry Data

Mobile networks now and in the future will consist of a massive number of devices, software applications, and technologies. Self-managed, zero-touch automated networks will be required to handle all these new devices and use cases. Realizing this full network automation requires two vital components.

Artificial intelligence and machine learning algorithms for comprehensive network automation: For instance, AI in network management can drastically cut the energy usage of future telecom networks.
Sensor and control data flow across all network model layers, including the physical layer: As networks grow in size and complexity, the management and orchestration (MANO) software needs more degrees of freedom and dials to turn.

These goals require smart optical equipment and components that provide comprehensive telemetry data about their status and the fiber they are connected to. The AI-controlled centralized management and orchestration layer can then use this data for remote management and diagnostics. We discuss this topic further in our previous article on remote provisioning, diagnostics, and management.

For example, a smart optical transceiver that fits this centralized AI-management model should relay data to the AI controller about fiber conditions. Such monitoring is not just limited to finding major faults or cuts in the fiber but also smaller degradations or delays in the fiber that stem from age, increased stress in the link due to increased traffic, and nonlinear optical effects. A transceiver that could relay all this data allows the AI controller to make better decisions about how to route traffic through the network.

A Smart Transceiver to Rule All Network Links

After relaying data to the AI management system, a smart pluggable transceiver must also switch parameters to adapt to different use cases and instructions given by the controller.

Let’s look at an example of forward error correction (FEC). FEC makes the coherent link much more tolerant to noise than a direct detect system and enables much longer reach and higher capacity. In other words, FEC algorithms allow the DSP to enhance the link performance without changing the hardware. This enhancement is analogous to imaging cameras: image processing algorithms allow the lenses inside your phone camera to produce a higher-quality image.

Figure 1 Simplified diagram of a network link with Forward Error Correction (FEC). — Figure 3: Simplified diagram of a network link with forward error correction (FEC). The FEC encoder adds redundant bits (overhead) to the transmitted data stream. The receiver can use this overhead to check for errors without asking the transmitter to resend the data.

A smart transceiver and DSP could switch among different FEC algorithms to adapt to network performance and use cases. Let’s look at the case of upgrading a long metro link of 650km running at 100 Gbps with open FEC. The operator needs to increase that link capacity to 400 Gbps, but open FEC could struggle to provide the necessary link performance. However, if the transceiver can be remotely reconfigured to use a proprietary FEC standard, the transceiver will be able to handle this upgraded link.

Reconfigurable transceivers can also be beneficial to auto-configure links to deal with specific network conditions, especially in brownfield links. Let’s return to the fiber monitoring subject we discussed in the previous section. A transceiver can change its modulation scheme or lower the power of its semiconductor optical amplifier (SOA) if telemetry data indicates a good quality fiber. Conversely, if the fiber quality is poor, the transceiver can transmit with a more limited modulation scheme or higher power to reduce bit errors. If the smart pluggable detects that the fiber length is relatively short, the laser transmitter power or the DSP power consumption could be scaled down to save energy.

Takeaways

Optical networks will need artificial intelligence and machine learning to scale more efficiently and affordably to handle the increased traffic and connected devices. Conversely, AI systems will also need faster pluggables than before to acquire data and make decisions more quickly. Pluggables that fit this new AI era must be fast, smart, and adapt to multiple use cases and conditions. They will need to scale up to speeds beyond 400G and relay monitoring data back to the AI management layer in the central office. The AI management layer can then program transceiver interfaces from this telemetry data to change parameters and optimize the network.

Tags: 800G, 800G and beyond, adaptation, affordable, AI, artificial intelligence, automation, CloudComputing, data, DataCenter, EFFECT Photonics, FEC, fiber quality, innovation, integration, laser arrays, machine learning, network conditions, network optimization, Networking, optical transceivers, photonic integration, Photonics, physical layer, programmable interface, scalable, sensor data flow, technology, Telecommunications, telemetry data, terabyte, upgrade, virtualization

What are FEC and PCS, and Why do They Matter

Insights

November 16, 2022

What are FEC and PCS, and Why do They Matter?

Coherent transmission has become a fundamental component of optical networks to address situations where direct…

Coherent transmission has become a fundamental component of optical networks to address situations where direct detect technology cannot provide the required capacity and reach.

While Direct Detect transmission only uses the amplitude of the light signal, Coherent optical transmission manipulates three different light properties: amplitude, phase, and polarization. These additional degrees of modulation allow for faster optical signals without compromising the transmission distance. Furthermore, coherent technology enables capacity upgrades without replacing the expensive physical fiber infrastructure on the ground.

However, the demand for data never ceases, and with it, developers of digital signal processors (DSPs) have had to figure out ways to improve the efficiency of coherent transmission. In this article, we will briefly describe the impact of two algorithms that DSP developers use to make coherent transmission more efficient: Forward Error Correction (FEC) and Probabilistic Constellation Shaping (PCS).

What is Forward Error Correction?

Forward Error Correction (FEC) implemented by DSPs has become a vital component of coherent communication systems. FEC makes the coherent link much more tolerant to noise than a direct detect system and enables much longer reach and higher capacity. Thanks to FEC, coherent links can handle bit error rates that are literally a million times higher than a typical direct detect link.

Let’s provide a high-level overview of how FEC works. An FEC encoder adds a series of redundant bits (called overhead) to the transmitted data stream. The receiver can use this overhead to check for errors without asking the transmitter to resend the data.

In other words, FEC algorithms allow the DSP to enhance the link performance without changing the hardware. This enhancement is analogous to imaging cameras: image processing algorithms allow the lenses inside your phone camera to produce a higher-quality image.

We must highlight that FEC is a block of an electronic DSP engine with its own specialized circuitry and algorithms, so it is a separate piece of intellectual property. Therefore, developing the entire DSP electronic engine (see Figure 2 for the critical component blocks of a DSP) requires ownership or access to specific FEC intellectual property.

Figure 2 Layout of the electronic engine used in a coherent optical transceiver, including the sequence the signal follows when processed by the engine.

What is Probabilistic Constellation Shaping?

DSP developers can transmit more data by transmitting more states in their quadrature-amplitude modulation process. The simplest kind of QAM (4-QAM) uses four different states (usually called constellation points), combining two different intensity levels and two different phases of light.

By using more intensity levels and phases, more bits can be transmitted in one go. State-of-the-art commercially available 400ZR transceivers typically use 16-QAM, with sixteen different constellation points that arise from combining four different intensity levels and four phases. However, this increased transmission capacity comes at a price: a signal with more modulation orders is more susceptible to noise and distortions. That’s why these transceivers can transmit 400Gbps over 100km but not over 1000km.

One of the most remarkable recent advances in DSPs to increase the reach of light signals is Probabilistic Constellation Shaping (PCS). In the typical 16-QAM modulation used in coherent transceivers, each constellation point has the same probability of being used. This is inefficient since the outer constellation points that require more power have the same probability as the inner constellation points that require lower power.

Figure 3: Comparison of conventional 16-QAM and a 16-QAM that uses Probabilistic Constellation Shaping (PCS). Diagram inspired by a figure from Infinera.

PCS uses the low-power inner constellation points more frequently and the outer constellation points less frequently, as shown in Figure 3. This feature provides many benefits, including improved tolerance to distortions and easier system optimization to specific bit transmission requirements. If you want to know more about it, please read the explainers here and here.

The Importance of Standardization and Reconfigurability

Algorithms like FEC and PCS have usually been proprietary technologies. Equipment and component manufacturers closely guarded their algorithms because they provided a critical competitive advantage. However, this often meant that coherent transceivers from different vendors could not operate with each other, and a single vendor had to be used for the entire network deployment.

Over time, coherent transceivers have increasingly needed to become interoperable, leading to some standardization in these algorithms. For example, the 400ZR standard for data center interconnects uses a public algorithm called concatenated FEC (CFEC). In contrast, some 400ZR+ MSA standards use open FEC (oFEC), which provides a more extended reach at the cost of a bit more bandwidth and energy consumption. For the longest possible link lengths (500+ kilometers), proprietary FECs become necessary for 400G transmission. Still, at least the public FEC standards have achieved interoperability for a large segment of the 400G transceiver market. Perhaps in the future, this could happen with PCS methods.

Future DSPs could switch among different algorithms and methods to adapt to network performance and use cases. For example, let’s look at the case of upgrading a long metro link of 650km running at 100 Gbps with open FEC. The operator needs to increase that link capacity to 400 Gbps, but open FEC could struggle to provide the necessary link performance. However, if the DSP can be reconfigured to use a proprietary FEC standard, the transceiver will be able to handle this upgraded link. Similarly, longer reach could be achieved if the DSP activates its PCS feature.

	400 ZR	Open ZR+	Proprietary Long Haul
Target Application	Edge data center interconnect	Metro, Regional data center interconnect	Long-Haul Carrier
Target Reach @ 400G	120km	500km	1000 km
Form Factor	QSFP-DD/OSFP	QSFP-DD/OSFP	QSFP-DD/OSFP
FEC	CFEC	oFEC	Proprietary
Standards / MSA	OIF	OpenZR+ MSA	Proprietary

Table 1: Summary of different use cases and standards for a 400G pluggable transceiver.

Takeaways

The entire field of communication technology can arguably be summarized with a single question: how can we transmit more information into a single frequency-limited signal over the longest possible distance?

DSP developers have many tools to answer this question, and two of them are FEC and PCS. Both technologies make coherent links much more tolerant of noise and can extend their reach. Future pluggables that handle different use cases must use different coding, error coding, and modulation schemes to adapt to different network requirements.

There are still many challenges ahead to improve DSPs and make them transmit even more bits in more energy-efficient ways. Now that EFFECT Photonics has incorporated talent and intellectual property from Viasat’s Coherent DSP team, we hope to contribute to this ongoing research and development and make transceivers faster and more sustainable than ever.

Tags: coherent, constellation shaping, DSP, DSPs, error compensation, FEC, PCS, power, Proprietary, reach, reconfigurable, standardized, standards

Insights

April 28, 2022

Co-Designing Optics and Electronics for Versatile and Green Transceivers

Network and data center operators need fast and affordable pluggable transceivers that perform well enough…

Network and data center operators need fast and affordable pluggable transceivers that perform well enough to cover a wide range of link lengths. However, power consumption and thermal management are the big obstacles in the roadmap to scale high-speed transceivers into Terabit speeds.

Over the last two decades, power ratings for pluggable modules have increased as we moved from direct detection to more power-hungry coherent transmission: from 2W for SFP modules to 3.5 W for QSFP modules and now to 14W for QSSFP-DD and 21.1W for OSFP form factors. Rockley Photonics researchers estimate that a future electronic switch filled with 800G modules would draw around 1 kW of power just for the optical modules.

Around 50% of a coherent transceiver’s power consumption goes into the digital signal processing (DSP) chip that also performs the functions of clock data recovery (CDR), optical-electrical gear-boxing, and lane switching. Scaling to higher bandwidths leads to even more losses and energy consumption from the DSP chip and its radiofrequency (RF) interconnects with the optical engine.

Figure 1: Normalized power breakdown of the internal blocks of a 400ZR pluggable module. Although this breakdown may vary a bit among different vendors, the authors find it to be generally true for various DSP-based modules, both IM-DD and coherent. Source: R. Nagarajan et al., IEEE JLT (2021)

Thus, a great incentive exists to optimize the interface between the module’s DSP chip and the optical engine to make the transceiver more energy efficient. This need for optimization and efficiency makes co-designing the optical and electronic systems of the transceiver more important than ever.

Co-Designing the Optimal DSP

Coherent DSPs are already application-specific integrated circuits (ASICs), but they could fit their respective optical engines and use cases even more tightly. Transceiver developers often source their DSP, laser, and optical engine from different suppliers, so all these chips are designed separately from each other. This setup reduces the time to market and simplifies the research and design processes but comes with trade-offs in performance and power consumption.

In such cases, the DSP is like a Swiss army knife: a jack of all trades designed for different kinds of PIC but a master of none. For example, many 400ZR+ transceivers used for telecom metro and long-haul applications are using the same DSPs as 400ZR transceivers used for much shorter data center interconnects. Given the ever-increasing demand for capacity and the need for sustainability both as financial and social responsibility, transceiver developers are increasingly in need of a steak knife rather than a Swiss army knife.

Co-designing the DSP chip alongside the photonic integrated circuit (PIC) can lead to a much better fit between these components. A co-design approach helps identify in greater detail the trade-offs between various parameters in the DSP and PIC and thus improve system-level performance optimization. A DSP optimized for a specific optical engine and application could save up to a couple of Watts of power compared to the usual transceiver and DSP designs.

Figure 2: Simplified diagram of the building blocks of a coherent QSFP-DD transceiver. Original diagram source: Infinera

Co-designing DSP Interfaces for Power Efficiency

Since the optical engine and DSP operate with signals of differing intensities, they need some analog electronic components to “talk” to each other. On the transmit side, the electronic driver block takes signals from the DSP, converts them to a higher voltage, and drives the optical engine. On the receive side, a trans-impedance amplifier (TIA) block will boost the weak signal captured by the optical detector so that the DSP can more easily process it. This signal power conversion overhead constitutes roughly 10-15% of transceiver power consumption, as shown in Figure 1.

Co-designing the DSP and PIC could enable ways to decrease this power conversion overhead. For example, the modulator of the optical engine could be designed to run at a lower voltage that is more compatible with the signal output of the DSP. This way, the DSP could drive the optical engine directly without the need for the analog electronic driver. Such a setup could save roughly two watts of power consumption!

Figure-dac grey blocks — Figure 3: Simplified diagram of the building blocks of a coherent QSFP-DD transceiver in which the DSP drives the optical engine directly from its digital-to-analog converter (DAC). This setup can achieve a power consumption improvement of 10-15%.

Co-design is also vital to optimize the transceiver layout floorplan. This plan must consider the power dissipation of all transceiver building blocks to avoid hot spots and thermal interference from the DSP to the highly thermally sensitive PIC. The positioning of all bond pads and interfaces is also very important for signal and power integrity, requiring a co-design with the package and substrate.

During this floorplan development, the RF interconnections between the DSP and PIC can be made as short as possible. These optimized RF interconnects reduce the optical and thermal losses in the transceiver package and will reduce the power consumption of the analog electronic driver and amplifier.

Co-Designing Fit-For-Purpose DSPs and PICs

As shown in Figure 4, a DSP chip contains a sequence of processing blocks that compensate for different transmission issues in the fiber and then recover, decode, and error-correct the data streams. Different applications might require slightly different layouts of the DSP or might not need some processing blocks.

Figure 4: Simplified diagram of the processing blocks of a DSP chip.

For example, full DSP compensation might be required for long links that span several hundreds of kilometers, but a shorter link might not require all the DSP functions. In these cases, a transceiver could turn off or reduce certain DSP functions—such as chromatic dispersion compensation—to save power. These power-saving features could be particularly useful for the cases of shorter data center interconnect links (DCI). On the optical engine side, the laser might not require a high power to transmit over this shorter DCI link so the amplifier functions could shut down. Co-designing the DSP and PIC allows a transceiver developer to mix and match these different energy-saving features to achieve the lowest possible power for a specific application.

Takeaways

Power consumption has become the big barrier that prevents pluggable transceivers from scaling up to 800G and Terabit speeds. Overcoming this barrier requires a tighter fit between the optics and electronics of the transceiver, especially when it comes to the interface between the optical engine and the electronic DSP. By co-designing the optical engine and the electronic DSP, transceiver developers could avoid the need for an external electrical driver and reduce transceiver power consumption by 10-15%. A co-design approach can also make it easier to design fit-for-purpose transceivers that implement power-saving features tailored to specific application cases.

The benefits of this co-design approach led EFFECT Photonics to incorporate talent and intellectual property from Viasat’s Coherent DSP team. With this merger, EFFECT Photonics aims to co-design our Optical System-On-Chip with the DSP to develop fit-for-purpose transceivers that are more energy-efficient than ever before.

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Tags: acquisition, coherent, coherent communication systems, coherent optical module vendor, DSP, FEC, forward error correction, green, green transceivers, high vertical integration, independent coherent optical module vendor, Integrated Photonics, optical digital signal processing, optical engine, optical transceivers, photonic integration, Photonics, pluggables, Transceivers, tunable laser, tuneability

Reconfigurable DSPs for Versatile Pluggables

Insights

April 20, 2022

Reconfigurable DSPs for Versatile Pluggables

Carriers must solve the dilemma of how to use small and affordable coherent pluggables while…

Carriers must solve the dilemma of how to use small and affordable coherent pluggables while still having enough performance and reach to cover most of their network links. At EFFECT Photonics, we believe coherent pluggables with an optical System-on-Chip (SoC) can play a vital role in solving this carrier’s dilemma and simplifying network upgrades. Meanwhile, these new coherent pluggables could also enable longer, and higher-capacity data center interconnects for more sustainable data center architectures.

Another big factor in making networks more affordable and sustainable is software-defined networks (SDNs) and automation. SDNs enable the network function virtualization (NFV), which allows operators to implement more functions to manage and orchestrate the network. Operators will reap even further benefits by using an artificial intelligence (AI) management and orchestration layer with the SDN/NFV layer, as shown in the figure below.

However, creating a fully automated network that can handle the ever-increasing amount of data and connected devices requires us to go beyond just adjusting the higher network layers. The orchestration and management software should also interface with the physical layer of the network, and that requires smart optical pluggable that adapt to varying network requirements. These requirements place additional burdens on digital signal processors (DSPs). DSPs are a vital component of coherent communication systems, as they perform the coding, decoding, and error corrections on the optical signal. Fortunately, the advances in electronic integration and standards make it so that a versatile coherent pluggable can benefit from an equally versatile and reconfigurable DSP.

Future Automated Networks Must Also Work on the Physical Layer

Telecom and datacom providers who want to become market leaders must scale up while also learning to allocate their existing network resources most efficiently and dynamically. SDNs can help achieve this efficient, dynamic network management. In a nutshell, the SDN paradigm separates the switching hardware from the software, allowing operators to virtualize network functions in a single centralized controller unit. This centralized management and orchestration (MANO) layer can implement network functions that the switches do not, allowing network operators to allocate network resources more intelligently and dynamically. This added flexibility and optimization will improve network outcomes for operators.

Figure 2: Comparing a traditional network approach (left) with an SDN/NFC approach (right).

However, the upcoming 5G networks will consist of a massive number of devices, software applications, and technologies. EFFECT Photonics believes that handling all these new devices and use cases will require self-managed, zero-touch automated networks. Realizing this full network automation requires two additional components alongside SDN and NFV:

Artificial intelligence and machine learning algorithms for complete network automation: For example, AI in network management will become a significant factor in reducing the energy consumption of future telecom networks.
Sensor and control data flow across all OSI model layers, including the physical layer: As networks get bigger and more complex, the management and orchestration (MANO) software needs more degrees of freedom and knobs to adjust. Next-generation MANO software needs to adjust and optimize both the physical and network layers to fit the network best.

Achieving the second goal requires smart optical equipment and components that can be diagnosed and managed remotely from the MANO layer. This context is where smart pluggable transceivers with reconfigurable DSPs come into play.

The Importance of Standardized Error Correction

Forward error correction (FEC) implemented by DSPs has become a vital component of coherent communication systems. FEC makes the coherent link much more tolerant to noise than a direct detect system and enables much longer reach and higher capacity. Thanks to FEC, coherent links can handle bit error rates that are literally a million times higher than a typical direct detect link. In other words, FEC algorithms allow the DSP to enhance the link performance without changing the hardware. This enhancement is analogous to imaging cameras: image processing algorithms allow the lenses inside your phone camera to produce a higher-quality image.

When coherent transmission emerged, all FEC algorithms were proprietary. Equipment and component manufacturers closely guarded their FEC because it provided a critical competitive advantage. Therefore, coherent transceivers from different vendors could not operate with each other, and a single vendor had to be used for the entire network deployment. However, vendors had to adapt with data center providers pushing disaggregation deeper into communication networks. Their coherent transceivers needed to become interoperable, so FEC algorithms needed standardization. The OIF 400ZR standard for data center interconnects uses a public algorithm called concatenated FEC (CFEC). In contrast, some 400ZR+ MSA standards use open FEC (oFEC), which provides a more extended reach at the cost of a bit more bandwidth and energy consumption. For the longest possible link lengths (500+ kilometers), proprietary FECs become necessary for 400G transmission. Still, at least the public FEC standards have achieved interoperability for a large segment of the 400G transceiver market.

A Smart DSP to Rule All Network Links

A smart pluggable transceiver that can adapt to all the applications we have mentioned before—data centers, carrier networks, SDNs—requires an equally smart and versatile DSP. It must be a DSP that can be reconfigured via software to adapt to different network conditions and use cases. For example, a smart DSP could switch among different FEC algorithms to adapt to network performance and use cases. For example, let’s look at the case of upgrading a long metro link of 650km running at 100 Gbps with open FEC. The operator needs to increase that link capacity to 400 Gbps, but open FEC could struggle to provide the necessary link performance. However, if the DSP can be reconfigured to use a proprietary FEC standard, the transceiver will be able to handle this upgraded link.

	400ZR	Open ZR+	Proprietary Long Haul
Target Application	Edge data center interconnect	Metro, Regional data center interconnect	Long-Haul Carrier
Target Reach @ 400G	120km	500km	1000 km
Form Factor	QSFP-DD/OSFP	QSFP-DD/OSFP	QSFP-DD/OSFP
FEC	CFEC	oFEC	Proprietary
Standards / MSA	OIF	OpenZR+ MSA	Proprietary

Table 1: Summary of different use cases and standards for a 400G pluggable transceiver.

Reconfigurable DSPs can also be beneficial to auto-configure links to deal with specific network conditions, especially in brownfield links. For example, the DSP can be reconfigured to transmit at a higher baud rate if the link has a good quality fiber. However, the DSP could be reconfigured to scale down the baud rate to avoid bit errors if the fiber quality is poor. If the smart pluggable detects that the fiber length is relatively short, it could scale down the laser transmitter power or the DSP power consumption to save energy.

Takeaways

A versatile pluggable that can handle different use cases – data center links, long metro links, and dynamic management and orchestration layers – must have the ability to use different coding and error coding schemes and adapt to different network requirements. The DSP must be equally versatile and switch among several operating modes – 400ZR, 400ZR+, proprietary – and error correction methods – cFEC, oFEC, and proprietary. Together with a programmable optical system on chip, the DSP can not just add software corrections but also make optical hardware changes (output power, turn amplifiers on/off) to adapt to different noise scenarios. Through these adjustments, the next generation of pluggable transceivers will be able to handle all the telecom carrier and data center use cases we can throw at it.

Press Releases

March 8, 2022

EFFECT Photonics Acquires Coherent Optical Digital Signal Processing Business from Viasat

EFFECT Photonics to Become the Most Highly Vertically Integrated, Independent Coherent Optical Module Vendor San…

EFFECT Photonics to Become the Most Highly Vertically Integrated, Independent Coherent Optical Module Vendor

San Diego, United States America – Today at OFC (Optical Fiber Conference) 2022, EFFECT Photonics, a leading provider of highly integrated optical communication products is announcing that it signed a definitive agreement to acquire coherent optical digital signal processing (DSP) and forward error correction (FEC) technology as well as a highly experienced engineering team from global communications company, Viasat Inc. (NASDAQ: VSAT).

Viasat is a long-established player in DSP and FEC technology. With eight generations of design IP, they have a proven track record of delivering successful field deployments.

From this acquisition, EFFECT Photonics will now own the entire coherent technology stack of all optical functions, including a high-performance tunable laser, together with DSP and FEC. This will enable the Company to deliver on its ambition to make high performance coherent communications solutions widely accessible and affordable. Furthermore, it will enable longer term economic and environmentally sustainable communications due to the ability to deliver high-end performance and reach within a small footprint and with lower power consumption. This opens the way to drive coherent technology into new places, revolutionizing the way the world interconnects.

This transaction is expected to provide the following customer benefits:

EFFECT Photonics will be able to optimize the complete solution for any application addressing both existing challenges and new possibilities
With full ownership of the key optical, DSP and FEC functions, EFFECT Photonics can offer seamless integration, cost efficiency and security of supply
EFFECT Photonics will be an independent vendor able to offer a full portfolio of building blocks such as the tunable laser and DSP, and/or complete solutions, increasing the choice reduced by recent mergers and acquisitions in the industry

EFFECT Photonics has also secured an additional $20M in Series-C funding bringing the total to $63M. Additionally, pursuant to the DSP acquisition agreement, Viasat will be joining EFFECT Photonics’ Supervisory Board and hold a minority interest in the Company.

“This is a significant step in accelerating our ambition to make coherent optical communications ubiquitous and further drive our product portfolio growth. We look forward to welcoming the team of highly skilled and experienced design architects and engineers who will be joining us to drive the development of energy efficient, high performance and affordable coherent solutions.

With all the recent changes in the industry landscape, this means that EFFECT Photonics is the only independent vendor able to deliver both the active optical components and the DSP. This will offer the market more choice and the ability to source superior solutions“
James Regan, CEO EFFECT Photonics.

“Given the trend of the fiber optic communications industry towards consolidation to provide vertically integrated end-to-end solutions, we believe that combining Viasat’s assets and capabilities with the unique integrated photonics capabilities of EFFECT Photonics will create substantially more market opportunities and better products. By investing in this Netherlands-headquartered company, we will also further expand our presence in Europe and be able to partner with EFFECT to bring state-of-the-art integrated photonics to Viasat’s own customers.”
Russell Fuerst, business area leader and vice president, Viasat.

–End of press release–

About EFFECT Photonics

EFFECT Photonics delivers highly integrated optical communications products based on its Dense Wavelength Division Multiplexing (DWDM) optical System-on-Chip technology. The key enabling technology for DWDM systems is full monolithic integration of all photonic components within a single chip and being able to produce these in volume with high yield at low cost. With this capability, EFFECT Photonics is addressing the need for affordable DWDM solutions driven by the soaring demand for high bandwidth connections. EFFECT Photonics is headquartered in The Netherlands, with additional facilities in the UK, the US and Taiwan, and a worldwide network of sales partners. http://www.effectphotonics.com

About Viasat

Viasat is a global communications company that believes everyone and everything in the world can be connected. For more than 35 years, Viasat has helped shape how consumers, businesses, governments and militaries around the world communicate. Today, the Company is developing the ultimate global communications network to power high-quality, secure, affordable, fast connections to impact people’s lives anywhere they are—on the ground, in the air or at sea. To learn more about Viasat, visit: www.viasat.com, go to Viasat’s Corporate Blog, or follow the Company on social media at: Facebook, Instagram, LinkedIn, Twitter or YouTube.

Copyright © 2022 EFFECT Photonics. All rights reserved. Viasat, the Viasat logo and the Viasat signal are registered trademarks of Viasat, Inc. All other product or company names mentioned are used for identification purposes only and may be trademarks of their respective owners.

Tags: acquisition, coherent, coherent communication systems, coherent optical module vendor, DSP, FEC, forward error correction, high vertical integration, independent coherent optical module vendor, Integrated Photonics, optical digital signal processing, optical engine, tunable laser, Viasat

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