APPLICATIONS & RESEARCH
Fraunhofer HHI in TERIPHIC terabit optical module drive
Data-transmitting light signal boosted by nanosized amplifier
Germany’s Fraunhofer Heinrich Hertz Institute has announced its participation in the innovative EU- Horizon 2020 research project TERIPHIC. This project, which formally kicked off in Berlin in late January, is taking place against a background of efforts to develop optical interfaces with Terabit capacity for datacom applications. The Institute notes that a practical path to the Terabit regime is to scale the current 400G modules. These are based (in the most forward- looking version of the standards) on four parallel lanes, each operating with PAM4 at 53 Gbaud. Scaling these modules by adding lanes looks simple, but entails challenges with respect to the fabrication and assembly complexity that can critically affect their manufacturability and cost. Netherlands, say that for the first time they have succeeded in connecting two parts of an electronics chip using an on-chip optical link. A light connection could, for example, be a safer means of connecting high-power electronics and digital control circuitry on one chip, without a direct electrical link. Until now, however, an optical link was not possible using standard silicon chip technology. Vishal Agarwal, a UT PhD student, has managed to do so. He worked out how to develop a very small optocoupler circuit that delivers a data rate measured in megabits per second, and in an energy-efficient way. Using light, it is possible to isolate one part of a Researchers of the University of Twente,
With international collaboration, researchers at Aalto University, Finland, have developed a nanosized amplifier to help light signals propagate through microchips. In their study published in Nature Communications, the researchers show that signal attenuation can be significantly reduced when data is transferred inside a microchip, for example, from one processor to another. “Photonics, or light transfer that is already widely used in internet connections, is increasingly being used by microcircuit systems because light is a more energy efficient and faster way of transferring data than electricity. The increase in information also requires an increase in performance. Boosting performance through electronic methods is getting to be very difficult, which is why we’re looking towards The researchers made their breakthrough with the help of a Finnish invention known as: the atomic layer deposition method. According to the team, this approach is ideal for processing various kinds of microcircuits, as it plays an important role in manufacturing the latest microprocessors. So far, the atomic layer deposition method has been used mainly in electronic applications. However, the newly released study indicates that photonics for answers,” commented doctoral candidate John Rönn.
possible applications also exist in photonics. In the development of photonics, new components must also ideally work cooperatively with electronics-based systems. “Silicon is a key material in electronics, and that’s why it’s also included in our light amplifiers together with the amplification element erbium,” said Rönn. “Today’s compound semiconductors, which are used, for instance, in LED technology, can also be used effectively in light amplification. That being said, most compound semiconductors are not compatible with silicon, which is a problem for mass production.” The Nature Communications study also shows that a light signal can be potentially boosted in all kinds of structures and that the structure of a microchip is not limited to a specific type. The results indicate that atomic layer deposition is a promising method for developing microchip photonic processes. “Our international collaboration made a breakthrough with one component: a nanosized amplifier. The amplification that we got was very significant. But we’ll still need more components before light can completely replace electricity in data transfer systems. The first possible applications are in nanolasers, and in sending and amplifying data,” says Professor Zhipei Sun.
TERIPHIC aims to address these challenges by leveraging photonic integration concepts and developing a seamless chain of component fabrication, assembly automation and module characterisation processes as the basis for high-volume production lines of Terabit modules. The project will bring together EML arrays in the O-band, PD arrays and a polymer chip that will act as the host platform for the integration of the arrays and the wavelength mux-demux of the lanes. The integration will rely on butt-end coupling steps, which will be automated via the development of module specific alignment and attachment processes on commercial equipment. The optical subassembly will be mounted on the mainboard of the module together with linear driver and TIA arrays. chip from another: the two different worlds will be able to communicate, but there is no electrical connection. In “smart power” chips, for example, the high-power part can be isolated from the digital control circuits. Such isolation ensures safe operation in applications like medical electronics and automotive systems. A so-called “optocoupler” is demanded by such situations, but until now, this has always been a relatively bulky device, and separated from the actual electronic chip. The ideal solution, proposed Agarwal, is to have an on-chip optocoupler, which he has now realised. electronics using standard chip technology (CMOS). It measures only 0.008 mm2 in size and consumes “minimal” energy. His optocoupler can be integrated with the
Light connects two worlds on single chip
Data-transmitting light signal boosted by nanosized amplifier
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ISSUE 16 | Q1 2019
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