The application of semiconductor optical amplifiers (SOAs) is not limited only to the amplification of optical signals. It is also used as an important element in optical switching, all-optical signal processing, demultiplexing, regeneration and wavelength conversion. The goal of this chapter is to present design criteria, improvement of the performance and integration of the SOA-based switches. We begin with a description of SOA-based switch architectures in the second section. The physical structure of an SOA, its features and characteristics are presented in the third section. Some techniques for SOA design improvements and a study of the noise in SOA-based switches are presented in the fourth section.