An optical communication system having a data transmitter which includes: at least one optical emission device to output light energy as an optical beam having an operating bandwidth; a beam dividing device to receive and divide the operating bandwidth into plural communication bands; a frequency presence modulation unit to: spectrally segregate the bandwidth of at least one communication band into plural channels, and modulate the bandwidth to selectively produce an optical output signal with wavelengths that correspond to one or more of the channels, wherein presence and absence of energy within channels constitute an information packet for data communication; a controller for providing a control signal to the frequency presence modulation unit to spectrally segregate the bandwidth of the at least one communication band into the plural channels; and a telescope to transmit the optical output signal.