Measurements on passive tunable optical filters for DWDM

Measurements on a passive optical fibre tunable filter are presented. The device is based on a loop mirror in a ring resonator. The loop mirror allows tuning by changing the coupling coefficient of a coupler. The novel filter structure allows planar optical integration for having higher free spectral ranges. Novel and simple design equations for the filter parameters and the tuning process are reported. There is a good agreement between measurements and theory.