A system, comprising: first signal processing circuitry for transmitting a signal including a plurality of data streams over a link, the first signal processing circuitry further comprising: first circuitry for processing each of the plurality of input data streams to generate a plurality of parallel pairs of data streams including an in-phase stream (I) and a quadrature-phase stream (Q) for each of the plurality of input data streams, modulating each of the plurality of parallel pairs of data streams with a selected one of at least three mutually orthogonal functions and each of the plurality of parallel pairs at a different signal bandwidth, respectively, to generate a plurality of data signals, each associated with one of the plurality of parallel pairs of data streams, and generating a plurality of composite data streams by overlaying at least one first data signal of the plurality of data signals in a first data layer with at least one second data signal of the plurality of data signals in a second data layer; second circuitry for processing the plurality of composite data streams to apply to each of the plurality of composite data streams a different function to apply a different Eigen mode, each of the different Eigen modes representing a different orbital angular momentum within the same frequency, with each of the plurality of composite data streams causing each of the composite data streams to be mutually orthogonal to each other and provide multiple orthogonal channels on the link to enable transmission of each of the plurality of composite data streams on the link at a same time over the multiple orthogonal channels; and third circuitry for selecting an encryption key for transmissions over the link using quantum key distribution. first circuitry for processing each of the plurality of input data streams to generate a plurality of parallel pairs of data streams including an in-phase stream (I) and a quadrature-phase stream (Q) for each of the plurality of input data streams, modulating each of the plurality of parallel pairs of data streams with a selected one of at least three mutually orthogonal functions and each of the plurality of parallel pairs at a different signal bandwidth, respectively, to generate a plurality of data signals, each associated with one of the plurality of parallel pairs of data streams, and generating a plurality of composite data streams by overlaying at least one first data signal of the plurality of data signals in a first data layer with at least one second data signal of the plurality of data signals in a second data layer; second circuitry for processing the plurality of composite data streams to apply to each of the plurality of composite data streams a different function to apply a different Eigen mode, each of the different Eigen modes representing a different orbital angular momentum within the same frequency, with each of the plurality of composite data streams causing each of the composite data streams to be mutually orthogonal to each other and provide multiple orthogonal channels on the link to enable transmission of each of the plurality of composite data streams on the link at a same time over the multiple orthogonal channels; and third circuitry for selecting an encryption key for transmissions over the link using quantum key distribution. <EOS>