We present a review of optical switch arrays using semiconductor optical amplifiers. The combination of active and passive switching components and of gate and booster amplifiers is discussed from the viewpoint of the relation between their designs and switching characteristics: loss compensation, crosstalk, spontaneous emission noise, and gain saturation. Demonstrations of carrier-injection type single-slip structure ( S 3) switch with traveling amplifier (COSTA) were reviewed to illustrate the device integration techniques and their potential usefulness in large-scale photonic switching systems even in the presence of spontaneous emission from integrated optical amplifiers.