This book is meant for researchers studying dense wavelength division multiplexing (DWDM), as well as graduate students, scientists, designers, development engineers, and technicians who are interested in the future of telephone, data, video, and Internet communication. The text's references may be helpful to readers who work in the telecom industry, such as component and systems designers. I hope that scientists and engineers in the fields of optics, spectroscopy, optronics, electro-optics, and micro/nano technology who are prepared to provide their skills to address some of the unresolved issues in telecommunications will also find this book to be helpful. On the other hand, this book might enable them to adapt some of the enormous advancements and financial commitments previously made in optical telecommunication to other sectors.