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Datacenter interconnects (DCIs) use optical fibers to connect two or more datacenters. DCI bandwidth is expected grow at more than 50% CAGR over the next five years. The short-distance DCI area (between 2 and 10 km) is of special interest for customers operating datacenters (e.g., Amazon, Google, Microsoft).

Current solutions are based on intensity modulation/direct detection (IMDD), where current speeds are up to 200 Gbit/s/wavelength. Energy efficiencies of around 20 pJoule/bit for the entire module are achieved (4 W/wavelength). Next generation solutions are expected to:

(i) Provide speeds of 800 Gbit/s per wavelength, i.e., a 4x increases with respect to the state of the art.
(ii) Operate under strict digital signal processing (DSP) power constraints (< 10 pJoule/bit).
(iii) Offer strict latency requirements (< 300 ns).

It is extremely difficult to achieve 800 Gbit/s/wavelength using IMDD technologies while maintaining a low power consumption in the DSP engine. It is now well-accepted by industry that the only viable way forward is by using light-coherent (also known as cheap coherent). In light-coherent, both the amplitude and the phase of the optical field carries information (unlike in IMDD, where only the amplitude is used).

The overall goal of the project is to develop DSP techniques for next-generation light-coherent transponders. The main idea is to design systems in terms of maintaining the complexity limited and not based on performance.