The invention relates to a
free space laser communication
system based on the
orbital angular momentum of light beams, which belongs to the technical field of optical applications. The
free space laser communication
system consists of an
optical fiber closely arranged
laser, four convex lenses, two polarizers, a space
optical modulator, a pinhole diaphragm, a beam expansion
system, a composite binary amplitude
grating and a
CCD detector. The
free space laser communication system takes the
optical fiber closely arranged laser with
gate control as a
light source, designs a phase
diffraction grating loaded onto the space
optical modulator according to the distribution of the light beams emergent from the
optical fiber closely arranged laser, and leads all the light beams to respectively havedifferent
diffraction orders and be positioned on a central shaft of the system, thereby constructing a central
diffraction light beam carrying gate information of the optical
fiber closely arranged laser. When the system works, the
gate control is carried out on the optical
fiber closely arranged laser according to data to be transmitted for realizing the modulation loading of the data to be transmitted; and the light beams carrying
data information utilize the composite binary amplitude
grating to detect the orbital
angular momentum state of the light beams at the receiving end of the system after transmitting for a certain distance in free space, thereby completing the
demodulation of the data transmitted by the communication system.