Ion exchange technique in the process of design and fabrication of passive devices for telecommunication has been a procedure to increment the glass refraction index and has received special attention because it improves surface-mechanical properties of glass and, more importantly, creates a wave-guiding region in the glass. Today, glass waveguides are considered to be suitable candidates for passive and active device for the integrated optical (IO) such as couplers, multiplexers, demultiplexers, and others. Their importance is borne out by their compatibility with optical fibers, low cost, low propagation loss, and integration into the system. In this way, with increasing speed of data transmission, the importance of integrated photonic devices and circuits grows. Many research groups have focused in the development of optical amplifier based on Erbium-doped materials since their potential to realize broadband and inherently linear compatible with current technology. This chapter gives an introduction to the ion exchange technique in solid matter, mainly optical glasses. I shall present the main results and equations describing the traditional ion exchange processes.