ABSTRACT
Fibers employed for long-haul transmission systems of large transmission capacity can only be of single-mode (SM) type. Since the SM light waveguide constitutes the crux of the whole technology of optical broadband (BB) transmission, brief mention will at least be made of a few of the basic properties. For the practical employment of SM fibers in BB transmission systems, initial interest is mainly directed at the losses and dispersion. The maximum transmittable power in the SM fiber is determined by nonlinear optical effects. In real SM fibers, the circular symmetry in an ideal waveguide is upset by geometrical effects by ellipticity of the fiber core and by mechanical strain. The difference in the effective refractive indices constitutes the birefringence. The most successful results were obtained hitherto in this connection from SM fibers with gradient index profiles exhibiting a triangular index profile.
