Recent advances in optical fibre communications

Optical fibers, expected to replace electric currents and copper wires in telephone networks as well as other communications systems, are discussed. Recently developed methods have produced both multimode graded-index fibers and single-mode fibers with attenuations as low as 0.5 dB/km at a realizable operating wavelength of 1.3 microns. Further, fibers have been made into cables with attenuations, after installations in the ground, of less than 5 dB/km at a wavelength of 0.85 micron. Bandwidth times length products are approaching 1 GHz km, with an expected improvement of at least one order of magnitude by using single-mode fibers at longer wavelengths. Considerable progress has been achieved in preserving fiber strength, as well as in developing techniques of jointing and coupling, and in improving the lifetime efficiency of suitable sources.