The application of coherent optical techniques to wide-band networks

The successful demonstration of optical heterodyne and homodyne techniques for point to point transmission links has led to an examination of their use in the context of wide-band systems. The high receiver sensitivity and frequency tuning ability potentially provide a means for accessing a significant part of the 50 000-GHz bandwidth provided by single-mode fiber. The possibilities for new network structures based on combinations of space, wavelength, and time switching are presented here, together with the concept of transparent networks which are not dependent on a particular modulation format or information rate.