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Energy-Efficient Multi-Terabit/s Photonic Interconnects

Final Report Summary - ENTERAPIC (Energy-Efficient Multi-Terabit/s Photonic Interconnects)

2 Publishable brief summary of the achievement of the project
The goal of EnTeraPIC was to explore, implement, and experimentally demonstrate novel concepts for massively parallel optical communications within and between data centers. A special focus of the project was on energy-efficient transmission and detection of wavelength-division multiplexing (WDM) data streams in chip-scale transceiver systems. To enhance scalability of such systems, EnTeraPIC combined chip-scale frequency comb sources with densely integrated silicon photonic and silicon-organic hybrid (SOH) photonic circuits. Within the project, device-level research was complemented by investigation of novel photonic-electronic signal processing concepts and by system-level demonstrations of multi-Terabit/s transmission.
In the framework of the project, a series of important achievements were made with respect to the project objectives: Novel chip-scale frequency comb sources based on electro-optic modulators, gain-switched semiconductor lasers, and Kerr-nonlinear microresonators were realized, and their viability was shown in a series of transmission experiments. Regarding integrated optical transmitter and receiver circuitry, the team was able to demonstrate silicon-organic hybrid (SOH) devices with unprecedented bandwidth and power efficiency. In this context, important proof-of-concept experiments were made, comprising, e.g. the first demonstration of 100 Gbit/s on-off-keying, the first generation of a 100 GBd 16QAM signal in a silicon-based electro-optic modulator as well as electro-optic modulation at energies of only a few femtojoules per bit. Moreover, it has been shown that silicon-organic hybrid integration enables novel concepts for energy-efficient signal processing, where electro-optic modulators can be directly driven by the output signals of state-of-the-art field-programmable gate arrays (FPGA), without the need for further drive amplifiers or digital-to-analog converters. Research on novel photonic devices was complemented by experimental demonstrations of data transmission at multi-Terabit/s line rates. In particular, we could perform the first coherent transmission experiments using Kerr frequency combs as optical sources, leading to overall data rates of more than 50 Tbit/s on 179 optical carriers that span the entire telecommunication C and L band. Equally important, we demonstrated coherent detection of a massively parallel WDM data stream by using a pair of microresonator Kerr soliton combs – one as a multi-wavelength light source at the transmitter, and another one as a multi-wavelength local oscillator (LO) at the receiver. This approach exploits the scalability advantages of microresonator soliton comb sources not only at the transmitter but also at the receiver side. In combination with advanced spatial multiplexing schemes, these results could bring petabit/s communication systems into reach.
Research in EnTeraPIC has led to a variety of novel concepts and aspects that go beyond the initially proposed work programme. As an example, the concept of photonic wire bonding was developed, implemented and experimentally demonstrated within the EnTeraPIC project, building the base of powerful hybrid photonic multi-chip modules that combine the distinct advantages of different integration platforms. These multi-chip modules lead to unprecedented flexibility and performance parameters that are clearly superior to those of comparable monolithically integrated systems. Moreover, a series of research results of EnTeraPIC were transferred to other application fields, comprising, e.g. optical metrology, biophotonics, and teratronics.
The findings of EnTeraPIC have been published in a series of highly cited articles in high-rank journals such as Nature, Nature Photonics, or other journals of the Nature Publishing Group. The strong scientific recognition of the research results obtained in EnTeraPIC is further witnessed by prestigious research prizes awarded to the principal investigator (PI) and by a series of more than 10 prizes awarded to team members at internationally recognized conferences. Besides opening new scientific directions, EnTeraPIC results show great potential for industrial application. This potential is explored in two ERC Proof-of-Concept Grants (HYPHEN, 680916; SCOOTER, 755380), one of which has already led to successful foundation of a start-up company in parallel to EnTeraPIC activities. The findings of EnTeraPIC have contributed greatly to establish and consolidate the PI’s research group and to strongly enhance the research environment.