Innovative photonics-based devices and measurement techniques for modern optical communications

The high demand for faster, more efficient and energy-conscious data transmission systems has fueled significant advancements in optical communication technologies. At the same time, the pressing need to address energy consumption in an energy constrained world has become a critical priority in information and communication technology. In my PhD activities, I reviewed how photonic analog to digital converters (PADCs) can overcome the performance limitations of electronic analog to digital converters (EADCs). My focus was particularly on spectrally sliced PADC architectures, given their importance in coherent receivers. Additionally, I conducted a review of the energy consumption characteristics of these PADCs as well as numerical study on waveguides and couplers. Aside the review works done on PADCs, and the numerical study of waveguides and couplers, the main objective of this thesis work is to demonstrate a new method of measuring dispersion in the case of a waveguide with chirped Bragg gratings. It is based on the fact that when coupling light into a waveguide using edge coupling, a fraction of the light will be reflected at the edge of the device and the rest will be transmitted. For this transmitted part of light, different frequencies will be reflected at different positions within the waveguide, due to the chirped Bragg gratings. The reflected light at the edge and within the waveguide will interfere to create a Michelson interferometric effect. By analyzing the combined reflected beams, the group delay can be calculated as the inverse of the spacing between the peaks, and the slope of the group delay is the dispersion of the device. An analytical model is also developed to calculate the dispersion of the device. It is important to note that the results obtained with both the experimental measurements and the analytical approaches are in good agreement with the designed dispersion value of the device. The approach proposed during my stay at the Department of Electrical and Photonics Engineering of DTU with Professor Galili’s group is fast, relative to the time required for measuring dispersion with the established methods. Moreover, it is a reliable technique based on the step-by-step procedure adopted in data processing. Finally, it is an accurate method because the results obtained are in good agreement with the designed values. This approach can represent an alternative to the established method for measuring dispersion, and its development for further applications will be the object of future work