Solutions to resolve data center traffic bottlenecks

The Electronics and Telecommunications Research Institute (ETRI) announced that it has succeeded in developing a fingernail-sized (1.3cm × 1.1cm) 400Gbps optical receiver module applicable to switching systems in large-capacity, mega data centers, and has transferred the technology to a related company.

This receiver is plugged into an optical transceiver to enable optical transmission, mounted on a line card, and embedded within a switching system, and is scheduled to be utilized in data centers.

To address traffic issues caused by the data big bang, ETRI has quadrupled the data transmission capacity per unit module from the existing 100Gbps to 400Gbps. Instead of the existing NRZ (No Modulation Zone) method, which sends 1 bit at a time, it adopted PAM-4 (4-level High-order Modulation), a next-generation high-efficiency transmission method that sends 2 bits at a time. This effectively makes the transmission speed four times faster.

With this, the research team reduced the number of components by half, decreased the footprint by more than 40%, and reduced power consumption by more than 25%. They also expect to reduce module costs by half.

The optical receiver module developed by the research team consists of an optical input, an optical multiplexer, a photodiode, and an electrical signal amplifier. They explained that the core of the optical receiver module technology lies in optical coupling technology and high-speed electrical signal interface technology.

Optical coupling technology refers to a technology that enhances optical performance during the process from the optical input to the photodiode. It reduces optical signal loss and minimizes inter-channel noise. ETRI announced that it has succeeded in localizing key components, such as parallel beam generators and lenses within optical receivers, in cooperation with domestic small and medium-sized enterprises.

High-speed electrical signal interface technology is a technique that amplifies the output signal of a photodiode and connects it to the outside while minimizing signal loss and distortion; therefore, ensuring linearity to maintain a uniform signal amplitude as the PAM-4 signal propagates is crucial.

Along with a 400Gbps optical receiver module, the research team simultaneously developed PAM-4 signal processing technology that generates and restores PAM-4 electrical signals. The technology was transferred to OISolution Co., Ltd.

ETRI announced that companies that received technology transfers are already receiving offers from overseas, and that plans for foreign exports are expected to materialize in the second half of this year.

During the development of this technology, the research team filed six key patents domestically and internationally regarding technologies to improve optical coupling efficiency and the practical application of PAM-4 modulation transmission and reception technology. They stated that they plan to further develop a 400Gbps optical transmitter this year to secure technology at the level of global leading companies and drive domestic small and medium-sized enterprises.

In addition, global data center IP traffic is projected to increase approximately threefold from 6.8 zettabytes (ZB) annually in 2016 to 20.6 ZB annually in 2021, at an average annual rate of 24.7%. Furthermore, the global data center optical transceiver market is predicted to grow at an average annual rate of 10%.

Yang Seon-hee, Head of the Network Research Division at ETRI, explained, “We expect the 400Gbps PAM-4 optical transceiver market to open up within the next two to three years. Securing 400Gbps PAM-4 optical receiver technology will be a new opportunity to create high added value.”