This invention discloses an optical interleaver. The optical interleaver includes an input port for receiving an input light beam including a plurality of wavelengths represented by &lgr;1, &lgr;2, &lgr;3, . . . , &lgr;n where n is a positive integer. The interleaver further includes a group of optical elements for decomposing the input light beam into a first light beam including a first set of wavelengths represented by &lgr;1, &lgr;3, &lgr;5, . . . , &lgr;n and a second light beam including of a second set of wavelengths represented by &lgr;2, &lgr;4, &lgr;6, . . . , &lgr;n−1, wherein the first light beam and the second light beam transmitted respectively in a first and second optical paths, and the group of optical elements further decomposing and generating two sets of mutually orthogonally polarized and parallel beam-components from the first beam and second beam. The interleaver further includes an incline angle means coupled to the group of optical elements. The incline angle means is used for projecting the two sets of mutually orthogonally polarized and parallel beam-components for the first and second beams respectively with a first incline angle and second incline angle relative to an optical axis of the interleaver. And, the interleaver further includes an output beam-component combining means for combining the mutual orthogonally polarized and parallel beam-components into a first output beam and a second output beam projected with the first and second incline angles respectively relative to the optical axis of the interleaver. In a preferred embodiment, the interleaver further includes a dual fiber collimator having a first optical fiber and a second optical fiber disposed off-axis of the collimator for directly receiving the first output beam and the second output beam projected respectively with the first and second inclined angles.