The wavelength-independent, non-reciprocal splitting properties of the
asymmetric, multimode Y-junction make it an ideal device for use as a
low-loss, low-power tap in a concatenated linear bus. The properties
of a two-dimensional slab model of the junction are investigated and t
he results of ray-tracing, modal and numerical beam propagation method
(BPM) techniques are compared. Minimization of splicing loss between
the ports of a square-core, three-dimensional buried channel waveguide
version of the device and a multimode fibre is also addressed.