An
optical interleaver is a 3-port passive
fiber-optic device that is used to combine two sets of
dense wavelength-division multiplexing (DWDM) channels (
odd and
even channels) into a composite signal stream in an interleaving way. For example, optical interleaver takes two multiplexed signals with 100 GHz spacing and interleaves them, creating a denser DWDM signal with channels spaced 50 GHz apart. The process can be repeated, creating even denser composite signals with 25 GHz or 12.5 GHz spacing.