Electroabsorption and electrorefraction were studied in GaAs/AlGaAs and InP/InAsP multiple quantum well waveguides. Measurements of changes of the absorption coefficient and the refractive index with wavelength and bias voltage were made. Switching ratios of up to 18 dB were obtained for the GaAs/AlGaAs material. The Kramers-Kronig relation was used to calculate the theoretical phase shifts from the absorption coefficient data. / Thesis / Master of Engineering (ME)