Abstract: This application disclosed an apparatus and process for tone frequency signaling. The apparatus comprises a transmitter to transmit a first signal, the first signal comprising a first data signal modulated onto a first carrier tone, a receiver to receive a second signal and monitor a characteristic of the second signal, the second signal comprising a second data signal modulated onto a second carrier tone, and a controller coupled to the transmitter and the receiver to change the frequency of the first carrier tone from a first frequency to a second frequency in response to the monitored characteristic of the second signal.

Abstract: A holographic element (HOE) with multiple apertures formed in a single substrate for use an optical communication system. The multi-aperture HOE can be use instead of an optics unit having one or more separate optical elements for each aperture needed by an optical transmitter, receiver or transceiver. The single substrate reduces complexity and cost relative to conventional system that the use separate optical elements to implement the optics unit.

Abstract: A free space (FSO) receiver includes an illumination sensing unit with multiple illumination apertures. The illumination sensing unit is used in deriving alignment information from portion(s) of a received FSO signal that are incident on the illumination apertures. The FSO receiver provides this information to the FSO transmitter that transmitted the FSO signal so that the FSO transmitter can adjust the direction it is pointing. The illumination apertures can be formed in a holographic optical element on a single substrate. Further, transmission, reception, tracking and/or spotting scope apertures may be formed in the single substrate.