“…Most work on interleaver filters in planar technology has been done in silica-based waveguide systems, especially by AT&T/Lucent [4,33,15,21,68,69] and NTT [70,7,3,71,2], but also others [72]. Temperature dependence in such filters can be compensated by introducing short grooves filled with a material having a thermo-optic coefficient of the opposite sign as that of silica [73].…”