Since 1970, optical fiber and optical communication technologies have been rapidly developing, causing a technology revolution in the communication industries. Due to much lower attenuation and interference, optical fiber has many advantages over existing copper wire in long-distance and high-demand applications. The revolution in communication industries also significantly reduces the prices of optical components and stimulates the development of optical fiber sensors. This book is aimed at providing extensive overviews of the theoretical and experimental aspects of the current optical communication technologies as well as fiber optic devices. Chapter 1 describes a multilevel transmission technique based on optical amplitude multiplexing (OAM). Fiber nonlinear effects are used to perform OAM of binary signals into multi-amplitude signals. Recently, passive optical networks (PONs) have gained a lot of interest because they minimize the number of required optical transceivers, reduce the fiber optic infrastructure, and the need to power the intermediate network nodes. They are very suitable for fiber to home (FTTH) networks that support high speed internet and video on demand services. Chapter 2 describes several commercial applications for multimode PON structures designed and constructed to include N-equivalent nodes. Chapter 3 reviews the effects of dispersion in fiber on Course WDM (CWDM) directly modulated system performance. The performance of fibers relative to positive or negative dispersion characteristics is discussed for the case of directly modulated lasers. The effects of chirp and fiber nonlinearity in a directly modulated 2.5-Gb/s transmission system are also shown by simulation. It is observed that enhanced system performance, which uses a positive dispersion fiber, can be achieved if positive chromatic dispersion in the optical fiber is equalized by SPM, whereas laser transient chirp can be compensated using a negative dispersion fiber.Chapter 4 reviews the design and application of X-ray lenses in the form of glass capillary filled by a set of concave epoxy micro-lenses. The fabrication and testing of compound refractive lenses (CRL) composed of micro-bubbles embedded in epoxy are discussed. The micro-bubble technique opens a new opportunity for designing lenses in the 8-9 keV range with focal lengths less than 30-40 mm. Chapter 5 demonstrates that direct detection CoWDM with Erbium-doped fiber amplifier (EDFA) amplification is only suitable for Terabit Ethernet transport over unrepeated spans of up to ~130 km. Raman amplification would allow for an increased system margin, Preface XI optic displacement sensor (FODS), lifetime measurements, microfiber loop resonator (MLR), and stimulated brillouin scattering.