A wide passband optical interleaver includes a first optical splitter, having a first output terminal and a second output terminal. A first optical route is coupled to the first output terminal. A second optical route is coupled to the second output terminal. A delay is coupled on the second optical route. A second optical splitter having two input terminals is receiving the first optical route and the second optical route. A plurality of optical filter respectively having transmission coefficients .rho..sub.i is coupled to the first optical route and the second optical route. The transmission coefficients .rho..sub.i are determined by satisfying a desired quantity of effective group delay ratio T, defined as.times..times..rho..rho..times..times..times..times..times..times. ##EQU00001## where S.sub.i is +1 or -1.