Long-wavelength optical fiber communication

Recent research on long-wavelength lightwave communication utilizing the wavelength region between 1.3 and 1.6 µm is reviewed with an eye toward future system development. The attraction of the long-wavelength region is the availability of the ultimately low-loss and wide-band features of the silica fiber, where minimum loss is 0.27 dB/km at a wavelength of 1.3 µm and 0.16 dB/km at 1.55 µm. The single-mode fiber has found its first significant applications in long-wavelength systems. The specific characteristics of lightwave components are discussed with focus on physical fundamentals. The practical performance of fibers and lightwave devices is surveyed. The dynamic properties of long-wavelength laser diodes are discussed in relation to fiber characteristics. The noise characteristics of long-wavelength detectors are considered for the purpose of specifying the repeater spacing. Some system studies are reviewed, for example, 1.3-µm-wavelength lightwave systems, which have demonstrated bandwidth-distance products of about 40 GHz ċ km. Various approaches to extend the capacity of long-wavelength lightwave transmission are given. In the future, the 1.5-µm wavelength system could operate at the lowest loss wavelength region extending from 1.5 to 1.65 µm. Much higher performance, for example, bandwidth-distance products of 185 GHz ċ km, achieved by further continuation of research and development on lightwave sources as well as fibers. Because of the author's familiarity with work in Japan, that work is emphasized and most frequently cited.