A broadband and flat-top wavelength response, which is required in WWDM sys
tems, has been realised for the first time by using planar-lightwave-circui
t (PLC) technology and lattice-form circuit composition theory. The filter
divides the signal every 20 nm with an insertion loss of 1.5dB and a 1 dB p
assband width of 16 nm.