An experimental study of propagation in multimode optical waveguides using spatially incoherent probe techniques

The analysis of propagation in waveguides is generally based Upon Maxwell's Equations and yields solutions in the form of sets of orthogonal fields called characteristic modes of the waveguide. If numerous modes are excited simultaneously by a single monochromatic source, the intensity distribution measured within the waveguide will be the coherent superposition of all the excited modal fields. The analysis of this coherent superposition is cumbersome for all but a small number of modes. If the source is polychromatic or spatially incoherent the increased complexity of the superposition procedure, which must now consider the relative coherence of modes, suggests that this method is inappropriate. [Continues.]