Patent ID: 7860401

Claim:
A system for point-to-point communication over an optical channel, the system comprising: a first modulated optical retro-reflector; a second modulated optical retro-reflector, wherein both the first and second modulated optical retro-reflectors are adjacent to each other and co-boresighted, and wherein an aggregate angular diameter of the first and second modulated optical retro-reflectors is contained within an angular Field of View (FOV) of an optic of an interrogator receiver, and wherein an aggregate linear diameter of the first and second modulated optical retro-reflectors is smaller than a spot size of an interrogating optical beam at the first and second modulated optical retro-reflectors; and a quadrature amplitude modulation (QAM) modulator unit coupled to both the first and second modulated optical retro-reflectors, wherein the quadrature amplitude modulation (QAM) modulator unit drives an amount of modulation generated by a first modulating structure in the first modulated optical retro-reflector and a second modulating structure in the second modulated optical retro-reflector, wherein the amount of modulation in the first modulated optical retro-reflector corresponds to an I value of an I symbol of a quadrature amplitude modulation (QAM) symbol for a piece of data and wherein the amount of modulation in the second modulated optical retro-reflector corresponds to a Q value of a Q symbol of the quadrature amplitude modulation (QAM) symbol for the piece of data.