Abstract: A space and wave division multiplexing and demultiplexing system and method for quantum key distribution (QKD) using free space laser communications. The system operates to transmit a quantum channel, including a key of QKD, included in a combined laser transmission with a classical channel, including an encrypted message of QKD. The laser transmission can be transmitted through free space to a lens, wherein it is diffracted into two separate diffraction patterns and captured by a double clad optical receiver fiber having an inner core and a concentric outer core. The diffraction pattern of the classical channel is captured by the outer core, while the diffraction pattern of the quantum channel is captured by the inner core, thus allowing separate treatment of each channel.

Abstract: An optical transmitter includes a beam steering system configured to direct an optical beam through a first optical element towards a second optical element. The beam steering system includes an adjustable optical element. The second optical element is susceptible to thermal and vibrational loads that disrupt an alignment between the first and second optical elements. The second optical element includes a main portion configured to direct the optical beam down a propagation path including a communications target. The second optical element also includes a reflective portion configured to direct an alignment portion of the optical beam back to the beam steering system through the first optical element. A detector is configured to receive the alignment portion and generate an alignment signal. A controller is configured to adjust the adjustable optical element based on the alignment signal to counteract the loads.