PhD Defence by Mads Lillieholm

Applications and Optimization of Optical Time Lenses based on Four-Wave Mixing in Highly Nonlinear Fibre


Principal supervisor: Prof. Leif Katsuo Oxenløwe, DTU Fotonik

Co-supervisor: Assoc. Prof. Michael Galili, DTU Fotonik

Co-supervisor: Lars Grüner-Nielsen, Danish Optical Fiber Innovation

Evaluation Board

Professor Karsten Rottwitt, DTU Fotonik

Research Fellow Marc Stephens, Aston University, Birmingham, UK

Professor Brian H. Kolner, W. W. Hansen Experimental Physics Laboratory, Stanford University 

Master of the Ceremony

Senior researcher, Radu Malureanu, DTU Fotonik


Research in optical signal processing (OSP) for optical communication is being pursued vigorously for its significant bandwidth advantage over electronics, and the potential for large energy savings at high data rates. Optical time lenses which are the temporal dual of conventional lenses, allow for a wide variety of useful ultrafast OSP applications, including e.g. optical Fourier transformations for conversion between the time and frequency domains, spectral or temporal magnification etc. So far, much of the research effort on time lenses has entailed the development of systems which can enable all-optical solutions for future highspeed and spectrally efficient communication systems.

In this thesis we investigate the characterization and optimization of highly nonlinear fibre (HNLF) for time lenses based on four-wave mixing, and demonstrate a time lens arrangement which enables an all-optical receiver for spectrally efficient communication through spectral magnification (SM). Conventional all-optical demultiplexing of orthogonal frequency-division multiplexing (OFDM) signals requires a receiver with complexity that increases with the number of data channels, and many active devices. In our scheme, it is possible demultiplex all data channels with passive filter banks, by magnifying the OFDM spectrum. Furthermore, the first characterization of SM in optimized HNLFs for higher order modulation formats demonstrates the feasibility of time lenses for multiple bits per symbol.


Thu 26 Oct 17
13:30 - 16:30


DTU Fotonik


Lyngby Campus

Bld./Aud.: 421/71