What Data Center Operators Need to Know About Expanding to 400GE Networks

Today, many data center operators need to expand their networks from 100GE to 400GE to support the bandwidth and response time required by emerging technologies such as fifth-generation wireless technology (5G), artificial intelligence (AI), virtual reality (VR), Internet of Things (IoT), and autonomous vehicles. In less than 15 years, data center network speeds have evolved from 10GE to 100GE. The implementation of 100GE networks in data centers began in 2014, but due to the availability of lower-priced fiber optic transceiver modules, expansion in the past few years has only made costs increasingly high. At the same time, the research and development of 400GE fiber optic transceivers is progressing smoothly and is expected to reach mature market pricing within a year of launch.

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The next generation of 400GE optical transceivers needs to use less power, cost less, and operate at four times the speed of 100GE optical transceivers. Modern hyperscale data centers can accommodate more than 50,000 optical fibers with optical transceivers at each end. Optical transceiver designers need to find a way to simultaneously increase channel capacity, ensure quality and interoperability, and reduce the cost of new 400GE optical transceivers.

Increase channel capacity

The transition from 100GE to 400GE is revolutionary, not evolutionary. Non-Return-to-Zero (NRZ) and Four-Level Pulse Amplitude Modulation (PAM4) are two modulation technologies that can enable 400GE. Each technology faces its own unique challenges. As speeds increase above 28Gb/s for Non-Return-to-Zero (NRZ) designs, channel loss in the transmission medium becomes a limiting factor. New multi-level signal modulation technologies, such as PAM4, are needed to overcome this limitation. However, PAM4 designs are more susceptible to noise.

In PAM4 designs, the signal-to-noise ratio (SNR) is lower, and analyzing the noise in transceiver designs becomes a critical test factor. PAM4 uses forward error correction (FEC) to address the lower signal-to-noise ratio (SNR) problem. FEC is an advanced coding technique that sends the required information through the link and payload data to correct errors. Physical layer testing of PAM4 signals must adapt to the new test challenges introduced by forward error correction (FEC).

Ensuring quality and interoperability

The nature of pluggable modules requires that any new fiber optic transceiver technology needs to be fully tested for compliance to specifications to ensure quality and seamless interoperability before being inserted into the network. Fiber optic transceiver manufacturers must ensure that their transceivers strictly adhere to established specifications and are interoperable with network components and fiber optic transceivers from different vendors. Network downtime due to transceiver failure is not an option for data center operators, who have already guaranteed service level agreements (SLAs) with users.

Fortunately, several standards organizations, such as the Institute of Electrical and Electronics Engineers (IEEE), the International Committee for Information Technology Standards (INCITS), and the Optical Internetworking Forum (OIF), manage optical transceiver specifications and define test procedures to ensure compliance with standards and interoperability with other vendors. There are different sets of optical and electrical tests for transmitters and receivers, and the channel effects between them also need to be considered. The faster and more complex the fiber optic system, the more time-consuming and challenging the characterization and compliance testing. By selecting a data center that has successfully passed all the physical layer characteristics and compliance tests defined by industry standards, operators can guarantee the quality and compatibility of their next-generation transceivers.

Reduce testing time and costs

The cost of a fiber optic transceiver is directly proportional to the complexity of the design and the number of optical components. Test time is also important and helps to reduce the overall cost of a fiber optic transceiver. The need to measure complex specifications according to defined standards complicates the design and verification process and requires a steep learning curve for test engineers.

Several techniques can significantly reduce test time and overall cost of transceivers from design simulation to device characterization and compliance and final manufacturing. Using innovative simulation techniques during the design phase ensures optimal success and higher yields. Powerful software simulation tools simplify the design process and enable post-processing and data analysis without re-running simulations. With software simulation, problems can be pinpointed early in the design cycle and costly manufacturing issues can be avoided later.

Engineers are still struggling with how to effectively test PAM4 modules in manufacturing production. However, once 400GE optical transceivers enter the manufacturing stage, real-time analysis and monitoring of data can drive manufacturing improvements and efficiencies, reducing the risk of failures and downtime. Quickly controlling operational or product quality issues can improve productivity and asset utilization, reducing testing time and costs.

Next Testing Challenge - Traffic Loading

Many data center operators are moving to virtualized networks using software defined networking (SDN) and network function virtualization (NFV). SDN is a network architecture that enables software programmable network control of virtualized network infrastructure. Network function virtualization (NFV) is an architectural concept that automates entire class of network node functions into building blocks that can be connected to build communication services. Once data center operators move to virtualized networks, they need to ensure that data flows as expected. And completing full network testing at Layers 2-7, which includes software defined networking (SDN/NFV) verification and traffic loading, will become the next hurdle to overcome.

Get ready for 5G technology and the Internet of Things

400GE fiber optic transceiver technology is emerging and will soon become a reality for data centers. As IoT devices rapidly increase to billions, and 5G technology enables new data-intensive applications with ultra-fast response times, data center operators upgrading their networks to 400GE will be ready to support them. Ensuring that 400GE fiber optic transceivers meet all required standards is the best way for data center operators to ensure a seamless migration from 100GE to 400GE using test solutions developed specifically to validate them.