This book consists of a total of nine chapters. Chapter 1 discuss the general introduction about the subject including a brief review of optical waveguides and switches as well as a brief outline of the objectives. Chapter 2 aim the study and design of optical gates such as NOT gate, AND gate, OR gate, universal gates (NAND/NOR) and XOR/XNOR gates. In Chapter 3, multiplier and comparator device based on Mach-Zehnder Interferometers (MZIs) have been...