Space-division multiplexing (SDM), which consists in exploiting multimode (MMF) or multicore fibers instead of single mode ones, is one of the future architectures to increase data rates and network planning flexibility. A desired working condition for SDM is the so called strong-coupling linear regime, which is however not intrinsically achievable in common MMFs. With this topic, the student has the chance to investigate if it would be achievable with some new design. If you are curious about it, just send a mail to paolo.carniello@tum.de.

Basics of Optical Communication Systems (see https://www.ce.cit.tum.de/en/lnt/teaching/lectures/optical-communication-systems/)

Optical communication systems rely on various modulation techniques to encode information onto light signals for transmission. Intensity modulation (IM) is a basic method of varying the intensity of a light wave according to the signal to be transmitted. IM can be performed, for example, with a directly modulated laser (DML) or an electro-absorption modulator (EAM). However, IM with a DML or an EAM unintentionally induces phase modulation. Understanding this phenomenon is crucial as it affects signal quality and transmission efficiency. The student's task is to understand why this unintended phase modulation is generated and to analyze its impact on the communication system.

The following literature can be helpful:

• ZHANG, Kuo, et al. Performance comparison of DML, EML and MZM in dispersion-unmanaged short reach transmissions with digital signal processing. Optics express, 2018
• KOBAYASHI, Soichi, et al. Direct frequency modulation in AlGaAs semiconductor lasers. IEEE Transactions on Microwave Theory and Techniques, 1982
• KREHLIK, P. Directly modulated lasers in negative dispersion fiber links. Opto-Electronics Review, 2007
• AMRO, Mohammad Yousif; SENIOR, John M. Chirp control of an electroabsorption modulator to be used for regeneration and wavelength conversion at 40 Gbit/s in all-optical networking. Photonic Network Communications, 2005

During the internship, the student will be researching the application of Neural Network-based signal predistortion to mitigate the effects of fiber chromatic dispersion in direct detection systems.

• basic Python skills beneficial