Optical Interleaving filters are attractive components in WDM systems especially narrower than 100GHz channel spacing system. Several types of interleaving filters have been proposed and realized. An interleaving filter is required to have the Box-like characteristics such as the periodic response, flat-passband, low insertion loss and low crosstalk. In addition, low chromatic dispersion (CD) is indispensable for DWDM systems. We focus on planar lightwave circuit interleaving filters. In this paper, we present interleaving filters with a tandem configuration of Fourier transform-based MZIs. The circuit using PLC technique is fabricated with high index contrast waveguides of Δ1.5%. We also have demonstrated monolithically integrated 1×4 (50-200GHz) interleaving filters and arrayed waveguide gratings(AWGs) with 200GHz-channel spacing suitable for interleaving WDM system.