Advances in lightwave systems research

Twenty years have passed since the first serious proposal was made to use a glass-fiber waveguide as a telecommunications transmission medium. Since then, vigorous research and development efforts have led to widespread applications of optical-fiber communication throughout the telecommunications industry. Today, lightwave systems research is exploring the vast potential bandwidth of low-loss single-mode fibers for long-haul and local-network applications. Laboratory systems with experimental single-frequency lasers and low-noise avalanche photodiodes have attained multi-gigabit-per-second transmission in single-mode fibers that are well over 100 km long. Coherent technology promises high receiver sensitivity and offers an efficient means for channel selection in a densely packed wavelength-multiplexed system. The first coherent-systems experiments have confirmed theoretical expectations but many challenges lie ahead. Other novel systems for local distribution and networking are also under study. This paper reviews recent research progress in these areas.