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Pluggables have becomes mainstream in datacom applications.

Insights

February 8, 2023

A Story of Standards: From 400ZR and Open ROADM to OpenZR+

Coherent optical transmission has been crucial in addressing network operator problems for the last decade. In this time, coherent technology has expanded from a solution reserved only for premium long-distance links to one that impacts data center interconnects, metro, and access networks…

The development of the 400ZR standard by the Optical Internetworking Forum (OIF) proved to be a milestone in this regard. It was the result of several years of progress in electronic and photonic integration that enabled the miniaturization of 400G coherent systems into smaller pluggable form factors. With small enough modules to pack a router faceplate densely, the datacom sector could profit from an ideal solution for high-capacity data center interconnects. Telecom operators wanted to implement a similar solution in their metro links, so they combined the Open ROADM standardization initiative with the 400ZR initiative to develop the OpenZR+ agreement that better fits their use cases.

This article will elaborate on these standardization projects—400ZR, OpenROADM, and OpenZR+—and explain what use cases each was designed to tackle.

What Is 400G ZR?

To cope with growing bandwidth demands, providers wanted to implement the concept of IP over DWDM (IPoDWDM), in which tunable optics are integrated into the router. This integration eliminates the optical transponder shelf and the optics between the routers and DWDM systems, reducing the network capital expenditure (CAPEX). This is shown in the figure below.

Figure 1: Implementation of a traditional coherent transport architecture (left), with the router connected to a transponder line card and a Reconfigurable Optical Add/Drop Multiplexer (ROADM). In contrast, an IPoDWDM solution (right) has 400ZR pluggable transceivers that go directly into the router and use passive multiplexing filters. The IPoDWDM solution eliminates the line card and additional optics, reducing network CAPEX.

However, widely deploying IPoDWDM with coherent optics forced providers to face a router faceplate trade-off. Since DWDM modules have traditionally been much larger than the client optics, plugging DWDM modules into the router required sacrificing roughly half of the costly router faceplate capacity. This was unacceptable for datacom and telecom providers, who approached their suppliers and the Optical Internetworking Forum (OIF) about the need to develop a compact and interoperable coherent solution that addressed this trade-off.

These discussions and technology development led the OIF to publish the 400ZR implementation agreement in 2020. 400ZR specifies a (relatively) low-cost and interoperable 400 Gigabit coherent interface for a link with a single optical wavelength, using a double-polarization, 16-state quadrature amplitude modulation scheme (DP-16QAM). This modulation scheme uses sixteen different constellation points that arise from combining four different intensity levels and four phases. It doubles the usual 16-QAM transmission capacity by encoding information in two different polarizations of light.

The agreement specified a link reach of 80 kilometers without amplification and 120 kilometers with amplification. For forward error correction (FEC), the 400ZR standard supports a concatenated FEC (CFEC) method. CFEC combines inner and outer FEC codes to enhance the performance compared to a standard FEC code.

The 400ZR agreement does not specify a particular size or type of module, but its specifications targeted a footprint and power consumption that could fit in smaller modules such as the Quad Small Form-Factor Pluggable Double-Density (QSFP-DD) and Octal-Small Form-Factor Pluggable (OSFP). These form factors are small enough to provide the faceplate density that telecom and especially datacom operators need in their system architectures. So even if we often associate the 400ZR standard with QSFP-DD, other form factors, such as CFP2, can be used.

What Is Open ROADM?

In parallel with the 400ZR standardization efforts, telecom network operators had a different ongoing discussion.

Reconfigurable Optical Add-Drop Multiplexers (ROADMs) were a game-changer for optical communications when they entered the market in the 2000s. Before this technology, optical networks featured inefficient fixed routes and could not adapt to changes in traffic and demand. ROADMs allowed operators to remotely provision and manage their wavelength channels and bandwidth without redesigning the physical network infrastructure.

However, ROADMs were proprietary hardware with proprietary software. Changing the proprietary ROADM platform needed extensive testing and a lengthy integration process, so operators were usually reluctant to look for other platform alternatives. Besides, ROADMs still had several fixed, pre-defined elements that could have been configurable through open interfaces. This environment led to reduced competition and innovation in the ROADM space.

These trends drove the launch of the Open ROADM project in 2016 and the release of their first Multi-Source Agreement in 2017. The project aimed to disaggregate and open up these traditionally proprietary ROADM systems and make their provisioning and control more centralized through technologies such as software-defined networks (SDNs, explained in the diagram below).

Figure 2: In a traditional network paradigm (left), switches contain both the hardware that forwards traffic (the data plane), as well as the software that sets the rules of where to forward said traffic (the control plane). The SDN paradigm (right) separates the switching hardware from the software, effectively decoupling the data plane from the control plane. The language between this controller and the switches is an open protocol, with OpenFlow being the most commonly used one. The Open ROADM initiative proposed its own open protocol called NETCONF.

The Open ROADM project defined three disaggregated functions (pluggable optics, transponder, and ROADM), all controlled through an open standards-based API that could be accessed through an SDN controller. It defined 100G-400G interfaces for both Ethernet and Optical Transport Networking (OTN) protocols with a link reach of up to 500km. It also defined a stronger FEC algorithm called open FEC (oFEC) to support this reach. oFEC provides a greater enhancement than CFEC at the cost of more overhead and energy.

What Is OpenZR+?

The 400ZR agreement was primarily focused on addressing the needs of large-scale data center operators and their suppliers.

While it had some usefulness for telecom network operators, their transport network links usually span several hundreds of kilometers, so the interface and module power consumption defined in the 400ZR agreement could not handle such an extended reach. Besides, network operators needed extra flexibility when defining the transmission rate and the modulation type of their links.

Therefore, soon after the publication of the 400ZR agreement, the OpenZR+ Multi-Source Agreement (MSA) was published in September 2020. As the diagram below explains, this agreement can be seen as a combination of the 400ZR and Open ROADM standardization efforts.

Figure 3: Diagram of how different elements from the 400ZR and Open ROADM standardization projects were combined to form the OpenZR+ MSA. Diagram provided by the OpenZR+ website.

To better fit the telecom use cases of regional and long-haul transport links, OpenZR+ added a few changes to improve the link reach and flexibility over 400ZR:

Using the more powerful oFEC defined by the Open ROADM standard.
Multi-rate Ethernet that enables the multiplexing of 100G and 200G signals. This provides more options to optimize traffic in transport links.
Support for 100G, 200G, 300G, or 400G transport links using different modulation types (QPSK, 8QAM, or 16QAM). This enables further reach and capacity optimization for fiber links.
Higher dispersion compensation to make the fiber link more robust.

These changes allow QSFP-DD and OSFP modules to reach link lengths of up to 480 km (with optical amplifiers) at a 400G data rate. However, the FEC and dispersion compensation improvements that enable this extended reach come at the price of increased energy consumption. While the 400ZR standard targets a power consumption of 15 Watts, OpenZR+ standards aim for a power consumption of up to 20 Watts.

If operators need more performance, distances above 500 km, and support for OTN traffic (400ZR and OpenZR+ only support Ethernet), they must still use proprietary solutions, which are informally called 400ZR+. These 400ZR+ solutions feature larger module sizes (CFP2), higher performance proprietary FEC, and higher launch powers to achieve longer reach. These more powerful features come at the cost of even more power consumption, which can go up to 25 Watts.

Takeaways

The following table summarizes the use cases and characteristics of the approaches discussed in the article: 400ZR, Open ROADM, OpenZR+, and 400ZR+.

Technology	400ZR	Open ROADM	OpenZR+	400ZR+ Proprietary
Target Application	Edge Data Center Interconnects	Carrier ROADM Mesh Networks	Metro/Regional Carrier and Data Center Interconnects	Long-Haul Carrier
Target Reach @ 400G	120 km (amplified)	500 km (amplified)	480km (amplified)	1000 km (amplified)
Target Power Consumption	Up to 15 W	Up to 25 W	Up to 20 W	Up to 25W
Typical Module Option	QSFP-DD/OSFP	CFP2	QSFP-DD/OSFP	CFP2
Client Interface	400G Ethernet	100-400G Ethernet and OTN	100-400G Ethernet (Multi-rate)	100-400G Ethernet and OTN
Modulation Scheme	16QAM	QPSK, 8QAM, 16QAM	QPSK, 8QAM, 16QAM	QPSK, 8QAM, 16QAM
Forward Error Correction	CFEC	oFEC	oFEC	Proprietary
Standards / MSA	OIF	Open ROADM MSA	OpenZR+ MSA	Proprietary

400ZR is an agreement primarily focused on the needs of data center interconnects across distances of 80 – 120 kilometers. On the other hand, OpenROADM and OpenZR+ focused on addressing the needs of telecom carrier links, supporting link lengths of up to 500 km. These differences in reach are also reflected in the power consumption specs and the module form factors typically used. The 400ZR and OpenZR+ standards can only handle Ethernet traffic, while the Open ROADM and 400ZR+ solutions can handle both Ethernet and OTN traffic.

Tags: 400ZR, Data center, demand, disaggregation, extend, fiber, interoperable, Open ROADM, power, size, ZR+

Insights

February 1, 2023

The Impact of Optics and Photonics on the Agrifood Industry

Precision farming is essential in a world with over 10 billion people by 2050 and…

Precision farming is essential in a world with over 10 billion people by 2050 and a food demand that is expanding at an exponential pace. The 2019 World Resources Report from the World Economic Forum warns that at the current level of food production efficiency, feeding the world in 2050 would require “clearing most of the world’s remaining forests, wiping out thousands more species, and releasing enough greenhouse gas emissions to exceed the 1.5°C and 2°C warming targets enshrined in the Paris Agreement – even if emissions from all other human activities were entirely eliminated.”

Technology can help the agrifood industry improve efficiency and meet these demands by combining robotics, machine vision, and small sensors to precisely and automatically determine the care needed by plants and animals in our food supply chain. This approach helps control and optimize food production, resulting in more sustainable crops, higher yields, and safer food.

Sensors based on integrated photonics can enable many of these precision farming applications. Photonic chips are lighter and smaller than other solutions so they can be deployed more easily in these agricultural use cases. The following article will provide examples of how integrated photonics and optical technology can add value to the agriculture and food industries.

How The World’s Tiny Agricultural Titan Minimizes Food Waste

The Netherlands is such a small country that if it were a US state, it would be among the ten smallest states, with a land area between West Virginia and Maryland. Despite its size, the Food and Agriculture Organization of the United Nations (FAO) ranked the Netherlands as the second largest exporter of food in the world by revenue in 2020, only behind the Americans and ahead of countries like Germany, China, or Brazil. These nations have tens or hundreds of times more arable land than the Dutch. Technology is a significant reason for this achievement, and the Dutch are arguably the most developed nation in the world regarding precision farming.

The hub of Dutch agrifood research and development is called the Food Valley, centered in the municipality of Wageningen in Gelderland province. In this area, many public and private R&D initiatives are carried out jointly with Wageningen University, a world-renowned leader in agricultural research.

When interviewed last year, Harrij Schmeitz, Director of the Fruit Tech Campus in Geldermalsen, mentions the example of a local fruit supplier called Fruitmasters. They employ basic cameras to snap 140 photographs of each apple that travels through the sorting conveyor, all within a few milliseconds. These photographs are used to automatically create a 3D model and help the conveyor line filter out the rotten apples before they are packaged for customers. This process was done manually in the past, so this new 3D mapping technology significantly improves efficiency.

These techniques are not just constrained to Gelderland, of course. Jacob van den Borne is a potato farmer from Reusel in the province of North Brabant, roughly a half-hour drive from EFFECT Photonics’ Eindhoven headquarters. Van den Borne’s farm includes self-driving AVR harvesters (shown in the video below), and he has been using drones in his farms since 2011 to photograph his fields and study the soil quality and farming yield.

The drone pictures are used to create maps of the fields, which then inform farming decisions. Van den Borne can study the status of the soil before farming, but even after crops have sprouted, he can study which parts of the field are doing poorly and need more fertilization. These measures prevent food waste and the overuse of fertilizer and pesticides. For example, Van den Borne’s farms have eliminated pesticide chemicals in their greenhouses while boosting their yield. The global average yield of potatoes per acre is around nine tons, but his farms yield more than 20 tons per acre!

If you want to know more about Van den Borne and his use of technology and data, you can read this article.

Lighting to Reduce Power Consumption and Emissions

Artificial lighting is a frequent requirement of indoor plant production facilities to increase production and improve crop quality. Growers are turning to LED lighting because it is more efficient than traditional incandescent or fluorescent systems at converting electricity to light. LED lights are made through similar semiconductor manufacturing processes to photonics chips.

LED lighting also provides a greater variety of colors than the usual yellow/orange glow. This technology allows gardeners to pick colors that match each plant’s demands from seedlings through cultivation, unlike high-pressure sodium or other traditional lighting systems. Different colors of visible light create different chlorophyll types in plants, so LED lights can be set to specific colors to provide the best chlorophyll for each development stage.

For example, suppose you roam around the Westland municipality of the Netherlands. You might occasionally catch a purple glow in the night skies, which has nothing to do with UFOs or aliens wanting to abduct you. As explained by Professor Leo Marcelis of Wageningen University (see the above video), researchers have found that red light is very good for plant growth, and mixing it with five to ten percent blue light gives even better results. Red and blue are also the most energy-efficient colors for LEDs, which helps reduce energy consumption even more. As a result, the farmers can save on light and energy use while the environment profits too.

Improving Communication Networks in the Era of Sensors

Modern farmers like Jacob van den Borne collect a large quantity of sensor data, which allows them to plan and learn how to provide plants with the perfect amount of water, light, and nutrients at the proper moment. Farmers can use these resources more efficiently and without waste thanks to this sensor information.

For example, Van den Borne uses wireless, Internet-of-Things sensors from companies like Sensoterra (video below) to gauge the soil’s water level. As we speak, researchers in the OnePlanet Research Center, a collaboration including the Imec R&D organization and Wageningen University, are developing nitrogen sensors that run on optical chips and can help keep nitrogen emissions in check.

These sensors will be connected to local servers and the internet for faster data transfer, so many of the issues and photonics solutions discussed in previous articles about the cloud edge and access networks are also relevant for agrifood sensors. Thus, improving optical communication networks will also impact the agrifood industry positively.

Takeaways

In a future of efficient high-tech and precision farming, optics and photonics will play an increasingly important role.

Optical sensors on a chip can be fast, accurate, small, and efficient. They will provide food producers with plenty of data to optimize their production processes and monitor the environmental impact of food production. Novel lighting methods can reduce the energy consumption of greenhouses and other indoor plant facilities. Meanwhile, photonics will also be vital to improving the capacity of the communications networks that these sensors run in.

With photonics-enabled precision processes, the agrifood industry can improve yields and supply, optimize resource use, reduce waste throughout the value chain, and minimize environmental impact.

Tags: atmosphere, demand, emissions, energy consumption, environment, future, high tech farming, high volume, Integrated Photonics, population growth, Precision agriculture, precision farming, process, resource, sensors, supply, waste

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