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Insights

June 22, 2022

What is DWDM and Why Should You Care?

Imagine a couple of small trucks moving along a country road in opposite directions, carrying…

Imagine a couple of small trucks moving along a country road in opposite directions, carrying goods between factories and consumers. As the population grows and demand increases, the trucks grow in number, and diversity of goods and traffic increases. City planners must start adding lanes until, eventually the tiny country road has become a large multi-lane highway with 18-wheelers moving vast volumes of different types of merchandise every day. A similar rapid expansion in ‘cargo’ has happened in telecommunications.

The telecommunications industry and service providers, in particular, have faced a dramatic and very rapid increase in the volume and type of data their systems must handle. Networks built initially to transmit soundwaves as electrical signals from one phone to another were now faced with managing data and video in real-time from many devices. Within approximately 30 years, we have moved from the introduction of the Internet and the creation of the Worldwide Web to the rollout of 5G wireless technology and the Internet-of-Things (IoT), through which virtually all devices can theoretically be interconnected.

Handling this exponentially increasing data traffic has required massive contributions from fiber optics and optical communications systems. In these systems, laser light carries much higher data transmission rates over greater distances than electrical signals. To encode the data into light, transmit it, and decode it back into electrical signals upon receipt, optical communication systems rely on optical transceivers. Dense Wavelength Division Multiplexing (DWDM) is a transceiver technology developed around 20 years ago that dramatically increases the amount of data transmitted over existing fiber networks. Data from various signals are separated, encoded on different wavelengths, and put together (multiplexed) in a single optical fiber.

The wavelengths are separated again and reconverted into the original digital signals at the receiving end. In other words, DWDM allows different data streams to be sent simultaneously over a single optical fiber without requiring new cables to be laid. In a way, it’s like adding more lanes to the information highway without having to build new roads!

Optical fiber with DWDM Channels — Figure 1: Example of a bidirectional DWDM system. At the central office, transceiver modules pick different wavelength channels for transmission, and these channels are combined into a single fiber through a device called a multiplexer. A demultiplexer splits the wavelength channels into separate fibers and the receiving modules on the remote end. Since this is a bidirectional system, transmission can go opposite too, from the remote end to the central office.

The tremendous expansion in data volume afforded with DWDM can be seen compared to other optical methods. A standard transceiver, often called a grey transceiver, is a single-channel device – each fiber has a single laser source. You can transmit 10 Gbps with grey optics. Coarse Wavelength Division Multiplexing (CWDM) has multiple channels, although far fewer than possible with DWDM. For example, with a 4-channel CWDM, you can transmit 40 Gbps. DWDM can accommodate up to 100 channels.

You can transmit 1 Tbps or one trillion bps at that capacity – 100 times more data than grey optics and 25 times more than CWDM. While the volume of data transmitted with DWDM is impressive, demand will continue to grow as we move toward IoT and 5G. Adding additional optical transceivers with different wavelengths to a fixed-wavelength DWDM system can significantly increase costs. Tunable DWDM transceivers allow you to control the wavelength (color) that the laser channel emits, adding flexibility and reducing cost. However, two obstacles prevented the broader deployment of DWDM technology.

First of all, installing and maintaining many new DWDM optical links was a time-consuming and costly process. Fortunately, the telecom industry developed a new weapon to face these challenges: self-tuning DWDM modules. Self-tuning DWDM modules minimize the network’s time-to-service by eliminating additional installation tasks such as manual tuning and record verification and reducing the potential for human error. They are host-agnostic and can plug into any third-party host equipment.

Furthermore, tunability standards allow modules from different vendors to communicate with each other, avoiding compatibility issues and simplifying upgrade choices. Self-tuning modules made the deployment and operation of DWDM links faster, simpler, and more affordable. The second issue had to do with size. DWDM modules were traditionally too large, so plugging them into a router required sacrificing roughly half of the expensive router faceplate capacity. Telecom operators could not accept such a trade-off. Advances in electronic and photonic integration overcame these trade-offs, miniaturizing coherent line card transponders into pluggable modules the size of a large USB stick.

Few companies worldwide supply DWDM technology with such compact sizes and self-tuning features. EFFECT Photonics is among them, and its tunable and cost-effective DWDM technologies will act as enablers of 5G and IoT, bringing the future to you today.

Tags: DWDM, Integrated Photonics, optical networking, optical technology, photonic integrated chip, photonic integration, PIC, programmable photonic system-on-chip

Coherent technology can give free-space optical systems greater reach and capacity, enabling these new applications in space and terrestrial links.

Insights

June 2, 2022

Free Space Optics for Access Networks

Optical signals are moving deeper and deeper into access networks. Achieving the ambitious performance goals…

Optical signals are moving deeper and deeper into access networks. Achieving the ambitious performance goals of 5G architectures requires more optics than ever between small cell sites. As stated in a recent report by Deloitte, “extending fiber optics deeper into remote communities is a critical economic driver, promoting competition, increasing connectivity for the rural and underserved, and supporting densification for wireless.”

However, there are cases in which fiber is not cost-effective to deploy. For example, a network carrier might need to quickly increase their access network capacity for a big festival, and there is no point in deploying extra fiber. In many remote areas, the customer base is so small that the costly deployment of fiber will not produce a return on investment. These situations must be addressed with some kind of wireless access solution. Carriers have used fixed microwave links for the longest time to handle these situations.

However, radio microwave frequencies might not be enough as the world demands greater internet speeds and simply changing over to higher carrier frequencies will limit the reach of microwave links. On top of that, the radio spectrum is quite crowded, and a carrier might not have the available licensed spectrum to deploy this wireless link. Besides, microwave point-to-point links produce plenty of heat while struggling to deliver capacity beyond a few Gbps. This is where free-space optics (FSO) comes into play.

FSO is a relatively straightforward technology to explain. A high-power laser source converts data into laser pulses and sends them through a lens system and into the atmosphere. The laser travels to the other side of the link and goes through a receiver lens system and a high-sensitivity photodetector converts those laser pulses back into electronic data that can be processed. In other words, instead of using an optical fiber as a medium to transmit the laser pulses, FSO uses air as a medium. The laser typically operates at an infrared wavelength of 1550nm that is safer on the eye.

Figure 1: Free space optical system diagram

FSO has often been talked about as some futuristic technology to be used in space applications, but it can be used more than that, including ground-to-ground links in access networks.FSO can deliver a wireless access solution that can be deployed quickly and with more bandwidth capacity, security features, and less power consumption than traditional point-to-point microwave links. Furthermore, since it does not use the RF spectrum, there is no need to secure spectrum licenses.

Overcoming the challenges of alignment, and atmospheric turbulence

FSO struggled to break through into practical applications despite these benefits because of certain technical challenges. Communications infrastructure, therefore, focused on more stable transmission alternatives such as optical fiber and RF signals. However, research and innovation over the last few decades are removing these technical barriers. One obstacle to achieving longer distances with FSO had to do with the quality of the laser signal.

Over time, FSO developers have found a solution to this issue in adaptive optics systems. These systems compensate for distortions in the beam by using an active optical element—such as a deformable mirror or liquid crystal—that dynamically changes its structure depending on the shape of the laser beam. Dutch startup Aircision uses this kind of technology in its FSO systems to increase their tolerance to atmospheric disruptions.

Figure 2: How an adaptive optical system works.

Another drawback of FSO is aligning the transmitter and receiver units. Laser beams are extremely narrow, and if the beam doesn’t hit the receiver lens at just the right angle, the information may be lost. The system requires almost perfect alignment, and it must maintain this alignment even when there are small changes in the beam trajectory due to wind or atmospheric disturbances.

FSO systems can handle these alignment issues with fast steering mirror (FSM) technology. These mirrors are driven with electrical signals and are fast, compact, and accurate enough to compensate the disturbances in the beam trajectory. However, even if the system can maintain the beam trajectory and shape, atmospheric turbulence can still degrade the message and cause interference in the data. Fortunately, FSO developers also use sophisticated digital signal processing techniques (DSP) to compensate for these impairments.

These DSP techniques allow for reliable, high-capacity, quick deployments even through thick clouds and fog. FSO links can now handle Gbps capacity over several kilometers thanks to all these technological advances. For example, a collaboration between Aircision and TNO demonstrated in 2021 that their FSO systems could reliably transmit 10 Gbps over 2.5 km. Aircision’s Scientific Director John Reid explained, “it’s an important milestone to show we can outperform microwave E-band antennas and provide a realistic solution for the upcoming 5G system.”

An alternative for safe, private networks

An understated benefit of FSO is that, from a physics perspective, they are arguably the most secure form of wireless communication available today. Point-to-point microwave links transmit a far more directional beam than mobile antennas or WiFi systems, which reduces the potential for security breaches. However, even these narrower microwave beams are still spread out enough to cover a wide footprint vulnerable to eavesdropping and jamming.

At a 1km distance, the beam can spread out enough to cover roughly the length of a building, and at 5km, it could cover an entire city block. Furthermore, microwave systems have side- and back lobes radiating away from the intended direction of transmission that can be intercepted too. Finally, if an attacker is close enough to the source, even the reflected energy from buildings can be used to intercept the signal.

Figure 3: Geometry of an FSO system vs. a microwave link. The microwave link has a much wider spread than FSO, which makes eavesdropping and jamming easier.

Laser beams in FSO are so narrow and focused that they do not have to deal with these issues. At 1km, a typical laser beam only spreads out about 2 meters, and at 5km, only about 5 meters. There are no side and back lobes to worry about and no near-zone reflections. The beam is so narrow that intercepting the transmission becomes an enormous challenge. An intruder would have to get within inches of a terminal or the line of sight, making it easier to get discovered. To complicate things further, the intruder’s terminal would also need to be very well aligned to pick up enough of a signal.

Using Highly-Integrated Transceivers in Free Space Optics

Even though fiber optical communications drove the push for smaller and more efficient optical transceivers, this progress also has a beneficial impact on FSO. As we have explained in previous articles, optical transmission systems have been miniaturized from big, expensive line cards to small, affordable pluggables the size of a large USB stick. These compact transceivers with highly integrated optics and electronics have shorter interconnections, fewer losses, and more elements per chip area. These features all led to a reduced power consumption over the last decade. At EFFECT Photonics, we achieve even further efficiency gains by an optical System-On-Chip (SoC) that integrates all photonic functions on a single chip, including lasers and amplifiers.

Figure 4: Diagram of an FSO system connected to an EFFECT Photonics 10G SFP+ pluggable transceiver via optical fiber.

FSO systems can now take advantage of affordable, low-power transceivers to transmit and receive laser signals in the air. For example, a transceiver based on an optical SoC can output a higher power into the FSO system. By using this higher laser power, the FSO does not need to amplify the signal so much before transmitting it, improving its noise profile. Furthermore, this benefit happens with both direct detect and coherent transceivers. This is a key reason why Aircision has partnered up with EFFECT Photonics to create both direct detect and coherent free-space optical systems, since the startup ultimately aims to reach transmission speeds of 100 Gbps over the air.

Takeaways

FSO has moved from the domain of science fiction to a practical technology that now deserves a place in access networks. FSO can deliver a wireless access solution that can be deployed quickly and with more bandwidth capacity, security features, and less power consumption than traditional point-to-point microwave links. Furthermore, since it does not use the RF spectrum, it is unnecessary to secure spectrum licenses. Affordable direct detect and coherent transceivers based on SoC can further improve the quality and affordability of FSO transmission.

Tags: access networks, adaptive optics, affordable, capacity, coherent, cost-effective, deployments, free space optics, integration, license, miniaturized, photonic integration, Photonics, pluggable, power consumption, private network links, quick deployments, radio spectrum, remote communities, security, SFP, signal processing, turbulence

The Light Path to a Coherent Cloud Edge Banner

Insights

May 25, 2022

Improving Edge Computing with Coherent Optical Systems on Chip

Smaller data centers placed locally have the potential to minimize latency, overcome inconsistent connections, and…

Smaller data centers placed locally have the potential to minimize latency, overcome inconsistent connections, and store and compute data closer to the end-user. These benefits are causing the global market for edge data centers to explode, with PWC predicting that it will nearly triple from $4 billion in 2017 to $13.5 billion in 2024. Cloud-native applications are driving the construction of edge infrastructure and services. However, they cannot distribute their processing capabilities without considerable investments in real estate, infrastructure deployment, and management.

This situation leads to hyperscalers cooperating with telecom operators to install their servers in the existing carrier infrastructure. For example, Amazon Web Services (AWS) is implementing edge technology in carrier networks and company premises (e.g., AWS Wavelength, AWS Outposts). Google and Microsoft have strategies and products that are very similar. In this context, edge computing poses a few problems for telecom providers too. They must manage hundreds or thousands of new nodes that will be hard to control and maintain.

At EFFECT Photonics, we believe that coherent pluggables with an optical System-on-Chip (SoC) can become vital in addressing these datacom and telecom sector needs and enabling a new generation of distributed data center architectures. Combining the optical SoCs with reconfigurable DSPs and modern network orchestration and automation software will be a key to deploying edge data centers.

Edge data centers are a performance and sustainability imperative

Various trends are driving the rise of the edge cloud:

5G technology and the Internet of Things (IoT): These mobile networks and sensor networks need low-cost computing resources closer to the user to reduce latency and better manage the higher density of connections and data.
Content delivery networks (CDNs): The popularity of CDN services continues to grow, and most web traffic today is served through CDNs, especially for major sites like Facebook, Netflix, and Amazon. By using content delivery servers that are more geographically distributed and closer to the edge and the end user, websites can reduce latency, load times, and bandwidth costs as well as increasing content availability and redundancy.
Software-defined networks (SDN) and Network function virtualization (NFV). The increased use of SDNs and NFV requires more cloud software processing.
Augment and virtual reality applications (AR/VR): Edge data centers can reduce the streaming latency and improve the performance of AR/VR applications.

Several of these applications require lower latencies than before, and centralized cloud computing cannot deliver those data packets quickly enough. As shown in Table 1, a data center on a town or suburb aggregation point could halve the latency compared to a centralized hyperscale data center. Enterprises with their own data center on-premises can reduce latencies by 12 to 30 times compared to hyperscale data centers.

Type of Edge		Data center	Location	Number of DCs per 10M people	Average Latency	Size
On-premises edge		Enterprise site	Businesses	NA	2-5 ms	1 rack max
Network (Mobile)	Tower edge	Tower	Nationwide	3000	10 ms	2 rack max
	Outer edge	Aggrega- tion points	Town	150	30 ms	2-6 rack max
	Inner edge	Core	Major city	10	40 ms	10+ rack max
Regional edge		Regional	Major city	100	50 ms	100+ racks
Not edge		Hyperscale	State/ national	1	60+ ms	5000+ racks

Table 1: Types of edge data centers and their characteristics. Source: STL Partners

Cisco estimates that 85 zettabytes of useful raw data were created in 2021, but only 21 zettabytes were stored and processed in data centers. Edge data centers can help close this gap. For example, industries or cities can use edge data centers to aggregate all the data from their sensors. Instead of sending all this raw sensor data to the core cloud, the edge cloud can process it locally and turn it into a handful of performance indicators. The edge cloud can then relay these indicators to the core, which requires a much lower bandwidth than sending the raw data.

Figure 1 Global data center traffic vs. useable data created per year. Graphic sourced from Cisco Global Cloud Index.

Edge data centers therefore allow more sensor data to be aggregated and processed to make systems worldwide smarter and more efficient. The ultimate goal is to create entire “smart cities” that use this sensor data to benefit their inhabitants, businesses, and the environment. Everything from transport networks to water supply and lightning could be improved if we have more sensor data available in the cloud to optimize these processes. Distributing data centers is also vital for future data center architectures. While centralizing processing in hyper-scale data centers made them more energy-efficient, the power grid often limits the potential location of new hyperscale data centers. Thus, the industry may have to take a few steps back and decentralize data processing capacity to cope with the strain of data center clusters on power grids. For example, data centers can be relocated to areas where spare power capacity is available, preferably from nearby renewable energy sources. EFFECT Photonics envisions a system of datacentres with branches in different geographical areas, where data storage and processing are assigned based on local and temporal availability of renewable (wind-, solar-) energy and total energy demand in the area.

Figure 2: High-speed fiber-optic connections allow data processing and storage to move to locations where excess (green) energy is available. If power is needed for other purposes, such as charging electric vehicles, data can be moved elsewhere

Coherent technology simplifies the scaling of edge data center interconnects

As edge data center interconnects became more common, the issue of how to interconnect them became more prominent. Direct detect technology had been the standard in the short-reach data center interconnects. However, reaching the distances greater than 50km and bandwidths over 100Gbps required for modern edge data center interconnects required external amplifiers and dispersion compensators that increased the complexity of network operations. At the same time, advances in electronic and photonic integration allowed longer reach coherent technology to be miniaturized into QSFP-DD and OSFP form factors. This progress allowed the Optical Internetworking Forum (OIF) to create the 400ZR and ZR+ standards for 400G DWDM pluggable modules. With small enough modules to pack a router faceplate densely, the datacom sector could profit from a 400ZR solution for high-capacity data center interconnects of up to 80km. If needed, extended reach 400ZR+ pluggables can cover several hundreds of kilometers. Cignal AI forecasts that 400ZR shipments will dominate in the edge applications, as shown in Figure 3.

Figure 3: Forecast of 100G port equivalents shipped for edge applications. These shipments are overwhelmingly 400ZR standard technology. Source: Cignal AI Transport Applications Report Q42021.

Further improvements in integration can further boost the reach and efficiency of coherent transceivers. For example, by integrating all photonic functions on a single chip, including lasers and optical amplifiers, EFFECT Photonics’ optical System-On-Chip (SoC) technology can achieve higher transmit power levels and longer distances while keeping the smaller QSFP-DD form factor, power consumption, and cost.

Maximizing Edge Computing with Automation

With the rise of edge data centers, telecom providers must manage hundreds or thousands of new nodes that will be hard to control and maintain. Furthermore, providers also need a flexible network with pay-as-you-go scalability that can handle future capacity needs. Fortunately, several new technologies are enabling this scalable and automated network management.

First of all, the rise of self-tuning algorithms has made the installation of new pluggables easier than ever. They eliminate additional installation tasks such as manual tuning and record verification. They are host-agnostic, can plug into any third-party host equipment, and scale as you grow. Standardization also allows modules from different vendors to communicate with each other, avoiding compatibility issues and simplifying upgrade choices. The communication channels used for self-tuning algorithms can also be used for remote diagnostics and management, such as the case of EFFECT Photonics NarroWave technology.

Automation potential improves further by combining artificial intelligence with the software-defined networks (SDNs) framework that virtualizes and centralizes network functions. This creates an automated and centralized management layer that can allocate resources efficiently and dynamically. For example, AI in network management will become a significant factor in reducing the energy consumption of future telecom networks.

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

Future smart transceivers with reconfigurable digital signal processors (DSPs) can give the AI-controlled management layer even more degrees of freedom to optimize the network. These smart transceivers will relay more device information for diagnosis, and depending on the management layer instructions, they can change their coding schemes to adapt to different network requirements

Takeaways

Cloud-native applications require edge data centers with lower latency, and that better fit the existing power grid. However, their implementation came with the challenges of more data center interconnects and a massive increase in nodes to manage. Fortunately, coherent pluggables with self-tuning can play a vital role in addressing these datacom and telecom sector challenges and enabling a new generation of distributed data center architectures. Combining these pluggables with modern network orchestration and automation software will boost the deployment of edge data centers. EFFECT Photonics believes that with these automation technologies (self-tuning, SDNs, AI), we can reach the goal of a self-managed, zero-touch automated network that can handle the massive scale-up required for 5G networks and edge computing.

Tags: 400ZR, artificial intelligence, cloud, coherent, computing, data centers, DSP, edge, edge data centers, infrastructure, latency, network, network edge, operators, optical system-on-chip, pluggables, self-tuning, services

Insights

May 4, 2022

The Growing Market for Tunable Lasers

The world is moving towards tunability. The combination of tunable lasers and dense wavelength division…

The world is moving towards tunability. The combination of tunable lasers and dense wavelength division multiplexing (DWDM) allows datacom and telecom industries to expand their network capacity without increasing their existing fiber infrastructure. Furthermore, the miniaturization of coherent technology into pluggable transceiver modules has finally enabled the widespread implementation of IP over DWDM solutions.

Self-tuning algorithms have also made DWDM solutions more widespread by simplifying their installation and maintenance. Hence, many application cases—metro transport, data center interconnects, and even future access networks—are moving towards coherent tunable pluggables. The market for coherent tunable transceivers will explode in the coming years, with LightCounting estimating that annual sales will double by 2026. Telecom carriers and especially data center providers will drive the market demand, upgrading their optical networks with 400G, 600G, and 800G pluggable transceiver modules that will become the new industry standards.

Figure 1: Market forecast for coherent DWDM modules by data rate. Source: LightCounting Market Forecast Report (April 2021)

Same Laser Performance, Smaller Package

As the industry moves towards packing more and more transceivers on a single router faceplate, tunable lasers need to maintain performance and power while moving to smaller footprints and lower power consumption and cost. Due to the faceplate density requirements for data center applications, transceiver power consumption is arguably the most critical factor in this use case.

In fact, power consumption is the main obstacle preventing pluggables from becoming a viable solution for a future upgrade to Terabit speeds. Since lasers are the second biggest power consumers in the transceiver module, laser manufacturers faced a paradoxical task. They must manufacture laser units that are small and energy-efficient enough to fit QSFP-DD and OSFP pluggable form factors while maintaining the laser performance. Fortunately, these ambitious spec targets became possible thanks to improved photonic integration technology.

The original 2011 ITLA standard from the Optical Internetworking Forum (OIF) was 74mm long by 30.5mm wide. By 2015, most tunable lasers shipped in a micro-ITLA form factor that cut the original ITLA footprint in half. In 2021, the nano-ITLA form factor designed for QSFP-DD and OSFP modules has once again cut the micro-ITLA footprint almost in half. The QSFP-DD modules that house the full transceiver are smaller (78mm by 20mm) than the original ITLA form factor. Stunningly, tunable laser manufacturers achieved this size reduction without impacting laser purity and power.

Figure 2: Evolution of tunable laser form factors for coherent optics (2011-2021). Figure from Laser Focus World.

Versatile Laser Developers for Different Use Cases

The different telecom and datacom applications will have different requirements for their tunable lasers. Premium coherent systems used for submarine and ultra-long-haul require best-in-class lasers with the highest power output and purity. On the other hand, metro transport and data center interconnect applications do not need the highest possible laser quality, but they need small devices with lower power consumption to fit router faceplates. Meanwhile, the access network space looks for lower-cost components that are also temperature hardened.

Table 1: Summary of different use cases for high-performance tunable lasers.

These varied use cases provide laser developers with ample opportunities and market niches to provide fit-for-purpose solutions for. For example, a laser module can be set to run at a higher voltage to provide higher output power and reach for premium long-haul applications. On the other hand, tuning the laser to a lower voltage would enable a more energy-efficient operation that could serve more lenient, shorter-reach use cases (links < 250km), such as data center interconnects.

An Independent Player in Times of Consolidation

With the increasing demand for coherent transceivers, many companies have performed acquisitions and mergers that allow them to develop transceiver components internally and thus secure their supply. LightCounting forecasts show that while this consolidation will decrease the sales of modulator and receiver components, the demand for tunable lasers will continue to grow. The forecast expects the tunable laser market for the transceiver to reach a size of $400M in 2026.

Figure 3: Global Market sales for high-performance modulators and receivers as well as tunable lasers. (Historical Data and Forecast). Source: LightCounting Market Forecast Report (April 2021)

We can dive deeper into the data to find the forces that drive the steady growth of the laser market. As shown in Figure 4, the next five years will likely see explosive growth in the demand for high-purity, high-power lasers. The forecast predicts that the shipments of such laser units will increase from roughly half a million in 2022 to 1.4 million in 2026 due to the growth of 400G and 800G transceiver upgrades. However, the industry consolidation will make it harder for component and equipment manufacturers to source lasers from independent vendors for their transceivers.

Figure 4: Units sold in the global market for Tunable Lasers components: legacy, high-purity low-power, and high-purity high-power (Historical Data and Forecast). Source: LightCounting Market Forecast Report (April 2021)

This data indicates that the market needs more independent vendors to provide high-performance ITLA components that adapt to different datacom or telecom provider needs. Following these trends, at EFFECT Photonics, we are not only developing the capabilities to provide a complete coherent transceiver solution but also the nano-ITLA units needed by other vendors.

Takeaways

The world is moving towards tunability. As telecom and datacom industries seek to expand their network capacity without increasing their fiber infrastructure, the sales tunable transceivers will explode in the coming years. These transceivers need tunable lasers with smaller sizes and lower power consumption than ever. Fortunately, the advances in photonic integration are managing to fulfill these laser requirements, leading to the new nano-ITLA module standards. However, even though component and equipment vendors need these tunable lasers for their next-gen transceivers, the industry consolidation can affect their supply. This situation presents an opportunity for new independent vendors to supply nano-ITLA units to this growing market.

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Tags: acquisition, coherent, coherent communication systems, coherent optical module vendor, coherent technology stack, datacenters, datacom, DWDM, high-performance, hyperscalers, independent, Integrated Photonics, lasers, noise, OEM, optical engine, optical transceivers, performance, photonic integration, Photonics, pluggables, power consumption, reach, self-tuning, Telecom, telecom carriers, Transceivers, tunable, tunable laser, tuneability, VARs, versatile

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

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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.

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

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.

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.

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 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 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.

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

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April 19, 2022

International growth opportunities for the photonics ecosystem, provided challenges around talent, scale-up and technology are solved

International growth opportunities for the photonics ecosystem, provided challenges around talent, scale-up and technology are…

International growth opportunities for the photonics ecosystem, provided challenges around talent, scale-up and technology are solved

Faster, lighter, more durable, and, at the end of the day, also much cheaper: the benefits of photonic circuits are considerable, for a wide range of applications. And the Netherlands plays an important role, globally, in the development and application of this key technology. In recent years, under the leadership of PhotonDelta, a solid foundation has been laid under the Dutch integrated photonics ecosystem. In the final episode of this series, we survey the playing field with Kathleen Philips (imec) and Boudewijn Docter (EFFECT Photonics). Read the whole series here.

Things are going well for the Dutch ecosystem around integrated photonics. Thanks to the perspectives shared by renowned representatives of this rapidly emerging industry in this series of articles, we learned that an international breakthrough is just around the corner. Obviously, this won’t be possible without a lot of investments. But in addition to that, general manager Kathleen Philips of imec at Holst Centre, three factors are all-important: choosing the right technology, growing into an ‘economy of scale’, and talent.

Imec’s headquarters are in Leuven; in the Netherlands, the renowned research institute is based in Eindhoven (as part of Holst Centre on the High Tech Campus) and Wageningen (with the OnePlanet Research Center). Although the Netherlands is primarily committed to Indium Phosphide (InP) and Silicon Nitride (SiN) production platforms, Kathleen Philips would like to make a case for internationalizing by joining CMOS-based work platforms such as Silicon Photonics (SiPh). “It offers the best opportunities for international support and that is essential for our growth ambitions.”

What is (integrated) photonics? Photonics is similar to electronics. However, instead of electrons, it uses photons (light) to transmit information. Photonic technology detects, generates, transports, and processes light. Current applications include solar cells, sensors, and fiber-optic networks. Photonic chips, officially called Photonic Integrated Circuits (PICs), integrate various photonic and often electronic functions into a microchip to make smaller, faster, and more energy-efficient devices. Because they are manufactured like traditional chips (with wafer-scale technology), mass production is also within reach – with price drop as a result. More here.

At imec, Kathleen Philips has an excellent overview of the status of photonics developments in the Netherlands and Belgium. She is thus able to combine the Dutch emphasis on Indium Phosphide and Silicon Nitride with the ‘Leuven’ expertise on Silicon Photonics. “We must be careful not to operate in ‘splendid isolation’. It is precisely in the hybrid combination of platforms that we find the desired connection to the world stage. Moreover, silicon photonics is largely compatible with classical and mainstream CMOS chip production lines, the value of which should never be underestimated. That said; if you need good lasers or low-loss waveguides, then InP and SiN platforms are an essential complement.”

Top-Notch

The next step is in creating an economy of scale, says Philips. “High volume is needed to lower the price of the end product. This automatically means you have to look across borders. Even a European scale is insufficient in that respect; we also have to focus on America and Asia. In photonics, you see the same development as in the semiconductor industry: the promise lies in the high volumes. We know that by scaling up the price goes down.”

The Netherlands has everything it needs to make that leap, Philips emphasizes. “You have to be top-notch to make an impact worldwide. And fortunately, we are. Our R&D is renowned, also historically. We are excellently positioned to connect with the big American flagships, for example. With Eindhoven, Twente and Delft we have academic gems. Their research, their publications, their professors, but also the rich ecosystem of start-ups around them and of course Photondelta: it’s all exactly how we would want to see it. Combine that with the presence of a solid high tech industry with major corporations such as ASML and NXP, and institutes like TNO and imec, and you know that a lot of good things are awaiting us.”

But, Philips warns, “to be successful we must be prepared to look beyond the important Dutch photonics industry and also strategically align ourselves internationally. In particular, the Dutch-Flemish axis offers wonderful opportunities and imec can play a connecting role. From Holst Centre in Eindhoven, we work closely with all the Dutch representatives of the ecosystem. Our colleagues in Leuven have strong international roots, with complementary technology and knowledge.” What helps, she adds, is that both at the Dutch and European level the realization has sunk in that governments can also help financially in this regard. Imec already makes use of Interreg subsidies, but the EU Chips Act is also full of promise in this regard. “And at a national level, there is a chance that the photonics sector can make use of the funding that is going to be distributed through the National Growth Fund. In short: there is much more awareness than before that public investment is important here.”

Talent

In a growth market, finding sufficient talent is always a challenge. In the photonics industry, it is no different. There is no shortage of good universities, says Philips. She mentions the three Dutch Universities of Technology, as well as those of Ghent, Leuven, and Brussels as important centers of expertise. “But you also need crown jewels: companies that capture the imagination so much that they manage to attract the best people, wherever they come from.” As an example, she points to EFFECT Photonics, founded in Eindhoven but grown – in a relatively short time – into a scale-up with some 250 people and offices around the world. “With that, EFFECT also shows how important scaling up is; not just for the company itself, but for our entire ecosystem.”

Indeed, the increasing awareness of EFFECT’s achievements has resulted in more talents knocking on their door. “But in addition to that, we also reach out to the talents ourselves,” adds founder Boudewijn Docter. “In fact, that’s one of the main reasons for our recent acquisition in the United States. We see that young people from all over the world have no trouble finding their way to Eindhoven. Recent graduates and PhDs, for example. They are very important, but we also need more experienced people and for them, it is often more difficult to leave hearth and home for a new workplace on the other side of the world.” And yet it is precisely those people who are desperately needed, Docter says. “The most important engineering skills can only be learned in practice. For the phase in which we are now, trial and error is no longer enough – we also need solid experience.”

This desire to hire more experienced people also leads to more remote work. “But even then, we would like people to come to Eindhoven from time to time, especially if they are working on multidisciplinary projects.” The best is a mix of young and experienced, in-house and remote. “With such a mix, young people find the best circumstances to grow, because they can take an example from their colleagues with a bit more experience.”

Volume

Docter is convinced that the choice to locate EFFECT’s business in places where the talent can be found ultimately also offers advantages for the Netherlands. “By growing all over the world, we become more visible as part of the national and European ecosystem. That in itself then attracts new talent, allowing the entire industry to grow.” This, in turn, is beneficial for this economy of scale also desired by Kathleen Philips. “In the semiconductor industry you always need volume”, Docter also says. “Because only then do you really start to notice the advantages. You have to know which markets you want to work for. For example, do you opt for a flexible design of your device, or a very specific one? Either way, you need to improve and stabilize your manufacturing process, which consists of hundreds of steps. Each step must deliver a 99.9999% yield, but it takes time to get there. Not only for us, by the way, but for all stakeholders in our industry, even the biggest ones. We have not yet built up sufficient experience for ‘First Time Right’, with the reliability that goes with such an ambition, but partly due to the focus on volume, we are already very well on our way to maturity.”

The imec model

Kathleen Philips is pleased that imec can play an important role in this global development. “The imec model, in which we set up R&D programs with various partners in a precompetitive setting, and our emphasis on the integration of different production platforms are essential. We are that neutral zone within which you can technically try out new ideas, and test a prototype in the value chain with limited costs. Sometimes this leads to the creation of new start-ups, or to collaboration with existing parties. But always it creates new or stronger ecosystems that the entire industry can benefit from.”

Tags: green, green transceivers, Integrated Photonics, optical transceivers, photonic integration, Photonics, pluggables, Transceivers, tuneability

Read about the latest technology trends, events, news, announcements and press releases regarding EFFECT Photonics.

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April 13, 2022

Solving the Carrier’s Dilemma with Optical Systems-On-Chip

In the coming decade, the network providers and countries with the most extensive installed base…

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March 15, 2022

Why Greener Transceivers are Profitable

Thanks to the incredible progress in energy-saving technologies (hyperscale datacenters, photonic and electronic integration), the…

Thanks to the incredible progress in energy-saving technologies (hyperscale datacenters, photonic and electronic integration), the exponential growth in data traffic for the next ten years will not lead to an exponential growth in ICT energy consumption. A 2020 study by Huawei Technologies estimates that from 2020 to 2030, global data traffic will grow 14 times while ICT energy consumption will just increase 1.5 times. Telecom operators, customers, employees, and investors are all paying more attention to sustainability.

A study commissioned by Vertiv surveyed 501 telecom enterprises worldwide, and 24% of them thought that energy efficiency should be their first priority when deploying 5G networks, while 16% saw it as their second priority. People are more likely to work for and buy products from companies with clear and ambitious sustainability goals. Investors and shareholders demand risk premiums from assets that underperform on climate goals, which often happens with fossil fuel companies. Such risk premiums could carry over to the telecom and datacom sectors. Sustainability is no longer just a matter of corporate social responsibility; it has real financial consequences.

Figure 1: Survey of 501 telecom enterprises worldwide about their priorities when deploying 5G networks. Commissioned by Vertiv and conducted by consulting firm STL Partners on January 2021.

However, there’s even more to the sustainability story. The telecom and datacom industries should become more sustainable not just because investors and customers like it, but also because it can lead to affordable ways to scale up capacity. After all, sustainable systems are efficient systems that are often smaller, more affordable, and require less energy spending. In this article, we will dive into one of an example of this trend by explaining how compact, fully-integrated optical transceivers can play an essential role in transitioning towards a greener and more affordable telecom infrastructure.

Telecom Equipment Dissipates Heat…and Money

Data centers and 5G networks might be hot commodities, but the infrastructure that enables them runs even hotter. Electronic equipment generates plenty of heat, and the more heat energy an electronic device dissipates, the more money and energy must be spent to cool it down. The Uptime Institute estimates that the average power usage effectiveness (PUE) ratio for data centers in 2020 is 1.58.

This number means that, on average, every 1 kWh required to power ICT equipment needs an additional 0.58 kWh for auxiliary equipment such as lighting and especially cooling. Datacenter PUE will decrease in the coming decade thanks to the emergence of hyperscale data centers, but the exponential increase of data traffic and 5G services also means that more data centers must be built too, especially on the network edges. For all the bad reputation that datacenters receive for their energy consumption, wireless transmission generates even more heat than wired links. While 5G standards are more energy-efficient per bit than 4G, the total power consumption will be much higher than 4G. Huawei expects that the maximum power consumption of one of their 5G base stations will be 68% higher than their 4G stations.

To make things worse, the use of higher frequency spectrum bands and new Internet-of-Things use cases requires the deployment of more base stations too. Prof. Earl McCune from TU Delft estimates that nine out of ten watts of electrical power in 5G systems turn into heat. This issue is why the Huawei also expects that the energy consumption of wireless access networks will increase even more quickly than that of data centers in the next ten years—more than quadrupling between 2020 and 2030.

Graph-estimated-electric-power — Figure 2: Comparison of estimated ICT electric power consumption in 2020 and 2030, divided by different ICT sectors. Source: Anders Andrae (Huawei), 2020.

These issues do not just affect the environment but also the bottom lines of communications companies. McKinsey reports that by the end of 2018, energy costs already represented 5% of operating expenditures for telecom operators. These costs will increase even further with the exponential growth of traffic and the deployment of 5G networks.

Compactness Makes Integrated Photonics Cool

Decreasing energy consumption and costs requires more efficient equipment, and a key to achieving this goal is to increase the use of photonics and miniaturization. Photonics has several properties that improve energy efficiency. Light transmitted over an optical fiber can carry more data faster and over longer distances than electric signals over wires, while dissipating less heat. Due to their longer reach, optical signals also save power compared to electrical signals by reducing the number of times the signal needs regeneration.

Photonics can also play a key role in rethinking the architecture of data centers. Photonics enables a more decentralized system of datacentres with branches in different geographical areas connected through high-speed optical fiber links to cope with the strain of data center clusters on power grids.

For example, data centers can relocate to areas where spare power capacity is available, preferably from nearby renewable energy sources. Efficiency can increase further by sending data to branches with spare capacity. The Dutch government has already proposed this kind of decentralization as part of their spatial strategy for data centers.

Figure 3: High-speed fiber-optic connections allow data processing and storage to be moved to locations where excess (green) energy is available. Data can be moved elsewhere if power is needed for other purposes, such as charging electric vehicles.

As we have explained in previous articles, miniaturization of telecom technology can also improve energy efficiency and affordability. For example, over the last decade coherent optical systems have been miniaturized from big, expensive line cards to small pluggables the size of a large USB stick. These compact transceivers with highly integrated optics and electronics have shorter interconnections, fewer losses, and more elements per chip area. These features all lead to a reduced power consumption over the last decade, as shown in the figure below.

Figure 4: Coherent module size and power consumption evolution from OIF MSA line card modules to pluggable modules like CFP and QSFP.

Transceivers can decrease their energy consumption further by using an optical System-On-Chip (SoC). The SoC integrates all photonic functions on a single chip, including lasers and amplifiers. This full integration leads to simpler and more efficient interconnections between optical elements, which leads to lower losses and heat dissipation. Optical SoCs also allow coherent transceivers to have a similar reach to line card transponders for use cases up to 400G, so the industry does not have to choose between size and performance anymore.

Wafer Scale Processes Make Integrated Photonics Affordable

Previously, deploying coherent technology required investing in large and expensive transponder equipment on both sides of the optical link. The rise of integrated photonics has not only reduced the footprint and energy consumption of coherent transceivers but also their cost. The economics of scale principles that rule the semiconductor industry reduce the cost of optical SoCs and the transceivers that use them. SoCs minimize the footprint of the optics, allowing transceiver developers to fit more optics within a single wafer, which decreases the price of each individual optical system. As the graphic below shows, the more chips and wafers are produced, the lower the cost per chip becomes.

Figure 5: Modelling of photonic integrated chip (PIC) cost as a function of aggregate number of PICs produced per year. Exponential increases in production lead to an exponential decrease in cost. Source: Model and graph provided by Prof. Meint Smit, TU Eindhoven.

Integrating all optical components—including the laser—on a single chip shifts the complexity from the expensive assembly and packaging process to the more affordable and scalable semiconductor wafer process. For example, it’s much easier to combine optical components on a wafer at a high-volume than it is to align components from different chips together in the assembly process. This shift to wafer processes also helps drives down the cost of the device.

Takeaways

Pluggable transceivers with compact, highly-integrated optics are more energy efficient and therefore save money in network operational expenditures such as cooling. They can even lead to datacenter architectures that make the most out of the existing electricity and processing resources, allowing cloud providers to make the most of their big infrastructure investments.

By integrating all the optical components in a single SoC, more of them can fit on a single wafer and scale up to higher production volumes. Thanks to the economics of scale, higher volume production leads to lower sales prices, which reduces operators’ capital expenditures too. Due to all the reasons described above, it should now be clear why these greener pluggable transceivers will become a key factor in the successful and profitable deployment of coherent technology in future access networks.

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Tags: green, green transceivers, Integrated Photonics, optical transceivers, photonic integration, Photonics, pluggables, Transceivers, tuneability

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February 10, 2022

Remote PHY, a new architecture for fixed access networks

Cable networks, just like any other telecom network in the world, had to adapt to…

Cable networks, just like any other telecom network in the world, had to adapt to the rising demand for data. During the 90s and 00s, these requirements led to the rise of hybrid fiber-coaxial (HFC) networks: optical fibers travel from the cable company hub and terminate into optical nodes, while coaxial cable connects the last few hundreds of meters from the optical node to nearby houses. These connections mainly were asymmetric, with customers having several times more bandwidth to download data than to upload.

In the past decade, the way we use the Internet has changed. With the rise of social media, online gaming, video calls, and independent content creation such as video blogging, users need more upstream bandwidth than ever. These new requirements have led to quick progress in the DOCSIS standards that regulate data transmission over coaxial cables. For example, the latest DOCSIS 4.0 standards allow full-duplex transmission with symmetrical upstream and downstream channels. Meanwhile, fiber-to-the-home (FTTH) systems—with fiber arriving directly to the customer premises—are also becoming widespread and allowing Gigabit connections that are faster than HFC networks.

Despite these upgrades in the transport mediums and standards, cable networks have experienced surprisingly few upgrades in their architectures. They still rely on centralized architectures in which the network operator’s headend performs almost all functionalities of both the physical layer (PHY) and medium access control layer (MAC). This means that the headend must modulate and demodulate data, convert between analog and digital, perform error corrections, provide cable modem termination system (CMTS) services, and do some resource allocation and flow control.

However, as traffic demands grow, cable providers need to deliver more and more bandwidth to their optical nodes and customer premises. The headend equipment is getting more congested, consuming more power, and running out of ports to handle more fiber connections. This solution centralized on the headend is struggling to scale up with increased demand. As it often happens in the telecom sector, operators need to figure out ways to deliver more bandwidth to more customers without spending significantly more money.

The multiple benefits of distributed access architectures

These issues are the reason why cable providers are moving into distributed access architectures (DAA) that can spread functionalities across access network nodes and reduce the port congestion and equipment required at the headend. Remote PHY has become increasingly popular among providers because it separates the PHY layer from the traditional cable headend and pushes its functions (such as modulation or digital-analog conversion) into the optical fiber access nodes of the network.

This shift can enhance the performance, capacity, and reliability of fixed access networks by using more digital transmission. It also reduces the complexity and power consumption of the headend, which previously translated into higher costs due to the required cooling.

Furthermore, separating PHY and MAC layers makes it easier to virtualize headends and their network functions, which significantly cuts expenses due to the use of commercial-off-the-shelf (COTS) equipment compared to more specialized equipment. Virtualization also allows deploying new services and applications more quickly to users and migrating workloads to optimize power consumption and reduce energy costs. On top of that, Remote PHY achieves all of these benefits while keeping the existing HFC infrastructure!

Figure 1: Comparison between traditional centralized architecture and Remote PHY architecture. The analog fiber link between cable headend and node is replaced by a digital link. The digital-to-analog conversion is moved from the cable headend in a centralized architecture to the Remote PHY node. In this new architecture, the new cable headend is called “CCAP Core”, as it doesn’t perform all the functions of a traditional Converged Cable Access Platform (CCAP) anymore.

Distributing digital-analog conversion

One of the most significant upgrades provided by Remote PHY networks is digital transmission deeper into the access network. In Remote PHY, data and video signals are kept in a digital format beyond the core headend, all the way into the upgraded optical node, where the signal is then converted into analog RF format. The fiber links between the headend and the access node that were previously analog will become digital fiber connections over Ethernet.

Since digital signals are more noise-tolerant than analog signals, the network benefits from this increased digital transmission length. Analog and radiofrequency signals now travel smaller distances to reach customer premises, so the signal accumulates less noise and boosts its signal-to-noise ratio. This improvement potentially allows the delivery of higher bandwidth signals to customers, including an increase in upstream bandwidth. Furthermore, the reliability of the link between the headend and the new optical node increases due to the greater robustness of digital links. These advances in reliability and performance make digital optics more affordable to buy and maintain than analog optics, reducing the costs for the network operators.

Let’s provide a very simplified example of how it all comes together. A network operator wants to increase their bandwidth and serve more customers, but their traditional centralized headend is already crowded with eight analog optical fiber links of 1Gbps each. There is no room to upgrade.

By installing Remote PHY technology in both the headend and the node, those analog links can be replaced by higher-capacity 10G digital links. The increased capacity at the headend allows for more optical node splits, while the new digital-to-analog conversion capability of the nodes allows them to care of more coaxial splits, all to serve new areas and customers.

Using DWDM in Remote PHY

The tremendous progress in electronic and photonic integration made Dense Wavelength Division Multiplex (DWDM) technology affordable and available to access networks, and this technology is quickly becoming a workhorse in this network domain. The availability of affordable DWDM transceivers made the deployment of Remote PHY even more powerful.

With Remote PHY improving the capacity of the headend, cable access networks had more bandwidth to serve more customers. However, some ways of using that bandwidth are more efficient than others. Operators can do extra node splits for customers by using their dark fibers and more grey transceivers, but that solution doesn’t scale in so cost-effectively due to the installation and maintenance of a new fiber link. Another option is time division multiplexing (TDM), which multiplexes the data of different node channels into specific time slots. This solution allows operators to carry different node channels in a single fiber but has speed, latency, and security trade-offs. A single time-multiplexed channel cannot transmit at the same speed and latency as a dedicated channel, and the data of all node channels are in the same multiplexed optical link, so the nodes and their customers can’t have fully secure channels to themselves.

DWDM solutions, on the other hand, can avoid the speed and security trade-offs by multiplexing extra channels into different wavelengths of light. Instead of several TDM channels “splitting” the 10G bandwidth among themselves, the DWDM channels can each transmit at 10G. And since each WDM channel has its own wavelength, the channels are transmitted independently from each other, allowing users to have secure channels.

Without sharing an optical link as in TDM, DWDM channels can also provide bidirectional communication (upstream and downstream) with less electronic processing than TDM channels. This feature is particularly beneficial for the modern Internet consumption patterns described earlier in the article.

Figure 2: Example of a Remote PHY architecture with a DWDM digital link. Without needing extra fibers, the link between the headend and node has a greater capacity to accommodate new customers, like those in the apartment complex.

Let’s go back to our previous example of the upgraded headend with 10G digital fiber links. Thanks to DWDM technology, a single 10G port on this headend can support additional optical nodes in the network more cost-effectively than ever. Let’s say a new apartment complex was built, and the network operator needs to deploy a new node to service this new building. In the past, this deployment would have required lighting up a dark fiber and setting up an extra fiber link or using TDM technology with lower data rates, latency, and security. With DWDM, the new node can simply be carried through a different wavelength channel in the already existing fiber link. And as we will describe in our next article, autotuneability in DWDM transceivers makes their setup and maintenance even more affordable.

Takeaways

Cable networks need to serve more customers than ever with more symmetric upstream and downstream capacity, and they need to achieve this without changing their existing fiber and coaxial infrastructure. These goals become possible with the onset of Remote PHY and more accessible DWDM transceivers. By separating the MAC and PHY layer, Remote PHY reduces the load on the cable headend and allows for more virtualization of network functions, making it easier and more affordable to upgrade and manage the network. Meanwhile, DWDM enables connections from the headend to the Remote PHY nodes that serve tens of customers with a single fiber.

Tags: architectuyre, autotuneability, DWDM, fixed access networks, Integrated Photonics, optical transceivers, photonic integration, Photonics, pluggables, remote phy, Transceivers, tuneability

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