Tropper joined the University of Southampton in 1983. She worked alongside David Hanna on the development of ytterbium -doped silica fibres, and together demonstrated their potential in λ = 1μm optical amplifiers. These amplifiers allowed for high power operation as well as the broad spectra bandwidths required to amplify ultrashort optical pulses. In 1988 Tropper and Hanna were the first to show that ytterbium -doped silica fibres could be used as an optical gain medium, and went on to investigate the spectroscopic properties that underpin its performance. Tropper's early work on ytterbium -doped silica fibres went on to influence Gérard Mourou. In 1989 Tropper was a founding member of the University of Southampton Optoelectronics group.