In this paper, the performance of a digital optical switch, operating at the infrared communications wavelength of 1550 nm and based on the thermo-optic effect in amorphous silicon, are investigated. We prove that the strong thermo-optic effect of amorphous silicon, combined with the possibility of realising micrometric integrated structures, allow the design of promising integrated switches. The device, designed for low-cost photonic applications, could be easily integrated in silicon optoelectronic circuits.