Ray Propagation in Beam-Waveguides with Redirectors

In a beam-waveguide, wanted and unwanted lens displacements from a straight line cause the beam propagating in either direction to depart severely from the guide axis. By including beam redirectors at each lens, it is shown that it is possible to reduce those displacements by amounts which depend (i) on the relative position of the lens where the beam deflection is sampled and of the redirector into which that information is fed, and (ii) on whether redirectors are sensitive to one or both directions of propagation. If transmission takes place in one direction only, it is better to place each redirector before its deflection sampling point (feed-forward control). If transmission occurs in both directions, it is advantageous to place each redirector after its deflection sampling point (feed-back control).