  We experimentally demonstrate an interferometric protocol for multiplexing
optical states of light, with potential to become a standard element in
free-space communication schemes that utilize light endowed with orbital
angular momentum (OAM). We demonstrate multiplexing for odd and even OAM
superpositions generated using different sources. In addition, our technique
permits one to prepare either coherent superpositions or statistical mixtures
of OAM states. We employ state tomography to study the performance of this
protocol, and we demonstrate fidelities greater than 0.98.
