A mode-evolution compound converter for processing an optical signal that includes a first component having a fundamental transverse magnetic (TM) mode and a second component having a fundamental transverse electric (TE) mode is disclosed. The compound converter includes a set of multiple converters connected to form a compound converter, wherein each converter is a mode-evolution converter selected from a group including a polarization converter, a spatial converter, and combination thereof, wherein the polarization converter at least converts a mode of a polarization of at least one component of the optical signal, and the spatial mode converter at least converts a spatial mode order of at least one component of the optical signal.