An apparatus for transmitting and receiving encoded optical signals having a data transmitter including: an 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; an optical pathway for bi-directional optical communication over a common optical path for transmitting the optical output signal and for receiving an optical input signal; and a data receiver to receive the optical output signal from the optical pathway.