A wavelength division multiplexing (WDM) transistor-outline (TO)-can assembly is provided that is capable of transmitting optical data signals having multiple wavelengths. The WDM TO-can assembly can be packaged in a relatively small package without requiring a large amount of plant retooling or capital investment, and that can be made available in the market relatively quickly. A plurality of the WDM TO-can assemblies can be incorporated into a small form factor or C form factor pluggable-type optical communications module to achieve high data rates.