The advent of high-quality single-frequency injection lasers (e.g., Refs. 1-3) for the 1.55-μm wavelength of minimum loss in single-mode silica fiber has made possible high-data-rate long-distance transmission. High bit rates over long distances were previously not possible in this fiber window because of the significant dispersion at 1.5 μm, and the multifrequency nature of long-wavelength Fabry-Perot lasers. While a number of sophisticated techniques. Including coherent modulation and heterodyne detection, show promise for future lightwave systems,4 the relative simplicity of direct modulation and detection continues to make this scheme attractive even as bit rates are pushed into the multigigabit regime.
© 1985 Optical Society of AmericaPDF Article