Multi-port optical coupling system using anamorphic lenses to correct for aberration

The present invention relates to optical couplers and especially to optical couplers adapted for coupling optical fibers and providing wavelength division mutliplexing of light to a plurality of fibers which are coupled, via the optical coupler, to a source of broad band light. In order to correct optical couplers, which couple light among optical fibers arranged at an input (light source) port and output ports which are spaced off the optical axis of the coupler for optical aberration, including astigmatic aberration, anamorphic lenses are used in the coupler instead of lenses with rotationally symmetric surfaces. The anamorphic lenses may be collimating and decollimating lenses arranged along an optical axis on opposite sides of a wave length beam splitting filter which reflects and transmits different portions of the source spectrum. These lenses are anamorphic lenses with toroidal surfaces instead of rotationally symmetric surfaces, as in such couplers of conventional design. The wave front error and the insertion loss of the coupler is substantially reduced providing a substantial improvement in coupling efficiency and in coupling system performance.