We present a model for electrorefraction based on the quantum confined Stark effect (QCSE) in strained InGaAs/InP chopped quantum wells (CQWs) consisting of three 27 Å InGaAs wells separated by 15 Å InP barriers. The model fully takes into account the influence of the thin interface layers around each well. We experimentally verify the model on a InGaAs/InP CQW which combines a large 60 meV QCSE redshift at 11.7 V bias with waveguide transparency at 1.55 µm, which is two times larger than in a InGaAsP quaternary well. The calculated electroabsorption spectra of the CQWs are in good agreement with experiment. We finally applied the Kramers–Kronig transformations for calculating the switching voltage in a Mach–Zehnder switch employing CQWs in the phase shifting section. The model was found to be in good agreement with experiment for both polarizations.