Features of the optical glass fibers in the long wavelength range are briefly mentioned. The present experimental transmission system is outlined. The systems are aiming at either long distance or high speed transmission. The present states of the art of important devices, lasers, LEDs, detectors and isolators are reviewed. Particularly long life has been attained. Peculiar features of GaInAsP alloy are discussed, considering the quaternary compositional freedom and the flexible nature of In-containing alloy. From the physical point of view, several proposals are given.