This paper describes the influence of optical networking on the design of optical fibers. It reviews fundamental optical properties, describes the various fiber types, discusses the fiber requirements for optical networking, and considers the effects of fiber nonlinearities. Finally, the paper describes three new optical fibers from Lucent Technologies that have been optimized for optical networks — TrueWave® RS (reduced slope) fiber, TrueWave XL (extra large) fiber, and AllWave™ fiber.