The necessity of different ultra-fast all-optical switches has received immense interest in recent years for optical parallel computation and information processing. Nonlinear Optical Loop Mirror (NOLM) provides a major support to optical switching based on all-optical logic and algebraic processing where the switching mechanism is based on Kerr nonlinearities of optical fibers. However more efficient and compact solutions can be realized by all optical switches using Semiconductor Optical Amplifiers (SOA) where the nonlinear coefficient is much higher. In this paper a concise review of semiconductor optical amplifier (SOA) based all-optical switches e.g., Terahertz Optical Asymmetric Demultiplexer (TOAD), Mach-Zehnder interferometer (MZI) switch and Ultra-fast non-linear interferometer (UNI) switches have been presented.