Propagation of Light Rays through a Lens-Waveguide with Curved Axis

The invention of the laser has revived interest in light as a communications carrier. One of the many problems which have to be solved before a light communications system becomes feasible is the propagation of a light beam from transmitter to receiver. It is well known1 that a sequence of converging lenses can guide a light beam and keep it from spreading. The losses of such a lens-waveguide can be calculated only by means of wave optics. However, even geometric optics can demonstrate the guiding properties of a lens-waveguide.2 It can show that a light beam, once it is injected into a sequence of lenses, follows an undulating path without wandering away from the axis of the lens-waveguide. The present paper is limited to describing the behavior of a light beam in a lens-waveguide whose axis is not straight everywhere, but which is allowed to follow bends of the transmission path or exhibit abrupt changes like tilts of its axis or an offset of one of its lenses from the axis on which all the other lenses are centered. The description is given in 741