A wavelength-division multiplexing (WDM) optical assembly with multiple collimator sets is disclosed herein. The WDM optical assembly includes a WDM optical core subassembly including at least one optical signal router, at least one WDM filter, and a first and second WDM collimator sets. The first WDM collimator set includes a first common optical collimator and at least two channel collimators and the second WDM collimator set includes a second common optical collimator and at least two channel collimators. At least a portion of the first WDM collimator set is optically positioned on a first surface of at least one substrate, and at least a portion of the second WDM collimator set is optically positioned on a second surface of the at least one substrate opposite the first surface. The WDM optical core subassembly increases lane density while decreasing size and minimizing complexity by using a plurality of WDM common ports.