This chapter presents an overview of the fiber development and the important features of the single- or even few-mode fibers currently attracting much interest for increasing the transmission capacity. It also provides an overview of advanced modulation techniques, presents the coherent detection and digital signal processing process and outlines the historical aspects of optical guiding and transmission techniques. Tremendous progress has been made though nearly the last 50 years due to two main significant phenomena, the guiding of lightwaves in optical fibers and transmission, and modulation and detection techniques. Since the proposed dielectric waveguides, the idea of transmission via an optical waveguide was like a lightening stroke through the telecommunication engineering, physics, and material engineering communities, alike. The detection of lightwaves evolves from direct to coherent, then direct self-homodyne, and then coherent homodyne with analog-to-digital processing. The chapter also presents an overview of the key concepts discussed in this book.