This book introduces undergraduate telecommunications students to the fundamentals of optical networks, combining theory and hands-on practice. It explores the evolution of optical telecommunications, highlighting the advantages of fiber optics, such as high bandwidth, low attenuation, and immunity to interference.The book covers essential topics, including light properties, fiber types, and challenges like attenuation and dispersion. Key components like LEDs, lasers, photodiodes, and amplifiers (EDFAs) are discussed alongside technologies like Wavelength Division Multiplexing (WDM). Modulation techniques (ASK, PSK) and detection methods (direct, coherent) are explained in detail.Network architectures such as FTTH and PON, high-speed systems (10G to 100G), and long-distance networks are thoroughly examined. Practical projects and simulations using OptiSystem provide students with real-world experience.Emerging trends like integrated photonics, 5G, Li-Fi, and quantum communications are also explored. This comprehensive guide equips students with the knowledge to navigate and contribute to the rapidly evolving field of optical telecommunications.