The demand for faster optical communication networks has been on the rise in the recent years. To address this demand, the new generation optical communication networks are moving towards very high data rates. Therefore, to achieve higher data rates, advance optical networks will require all optical ultra-fast signal processing. Various operations have been proposed in the field of optoelectronic computing in last three decades. Nonlinear Optical Loop Mirror (NOLM) provides a major support to optical switching based all-optical logic and algebraic processing where the switching mechanism is based on fiber Kerr nonlinearities. However, due to the weak Kerr coefficient in fibers, long fibers and high optical powers are necessary. More efficient and compact solutions can be realized by all optical switching in semiconductor optical amplifiers (SOAs) where the nonlinear coefficient is much higher. In this paper a brief review is made on different types of SOA non-linearities.