We demonstrate all-optical switching in quantum dots (QDs). The switching is studied in an integrated optical combiner circuit. This is a Mach–Zehnder interferometer with an unequal power distribution over the branches. The refractive index is intensity dependent in the branches due to the QDs. Large all-optical nonlinearities are measured. This device is aimed to avoid an unwanted 3-dB loss, fundamental in passive optical splitters.