The inventors propose herein a novel band filter design for planar lightwave
circuits. In one embodiment of the present invention, the band filter includes
two waveguide grating routers connected by sets of substantially equal path length
waveguides within each set separated on one side, wherein the waveguides of each
set are formed such that optical signals having overlapping frequency ranges are
propagated through adjacent waveguides. In addition, the waveguides of each set
are spaced at their connection to the second waveguide grating router such that
optical signals with predetermined optical frequency ranges are routed to selected,
respective output ports. Some of the advantages of this novel band filter include
compactness, sharp passband corners, and a lack of chromatic dispersion.