Optical communication links over single mode glass fibers are used for almost all recent ultra-fast data connections, like the back bone of the internet or interconnects between datacenters. The increasing amount of cloud and video-on-demand services requires higher transmission speeds and therefore updated communication systems.

There are different common ways to increase the data rate of a fiber optic communication link: one can use higher order modulation formats (also jointly with probabilistic shaping), simply deploy more fibers (which is expensive), use wavelength division multiplexing (already mostly exploited), or try to modulate different modes of a multi-core or multi-mode optical fiber, which are orthogonal transversal distributions of the optical field in the waveguide.

The capacity of the optical fiber channel is limited by its inherent nonlinear nature. One effect - among others - is a nonlinear distortion of the propagating signal's phase, which in principle can be conmpensated with digital back propagation, but requires way too much processing power for state-of-the-art digital signal processing.

An alternative technique is optical phase conjugation to compensate fiber nonlinearities, where lumped devices are inserted in the fiber link, which invert the signal's phase front. If repeatedly done, phase distortions can be corrected in the optical domain. The conjugation can be realized with integrated silicon devices, where the incident signal and two pump lasers interact over (nonlinear) Four Wave Mixing (FWM) and generate the conjugated and amplified outbound signal. The FWM efficiency can be increased if the light waves are in different modes of the silicon waveguide. In my research, I am focusing on numerical simulations of waveguide modes and the related nonlinear signal propagation.