| 摘要 |
The communications system according to the invention includes a sending station (1) equipped with a laser source (10) sending a beam of coherent light waves with basic frequency (Fo) modulated by a carrier frequency of the useful signal corresponding to the information to be transmitted, and a receiving station able to pick up this information from a beat signal formed by mixing the beam (F') originating from the sending station (1) and a beam of waves (Fi) originating from a local oscillator (23). The beam (F) sent by the sending station includes a reference subbeam (F1) of unmodulated waves with base frequency (Fo) forming a reference signal and a useful subbeam (F2) the waves of which are modulated on a carrier via an acoustooptical cell (12) in order to form a useful information signal; the receiving station (2) includes a non-linear crystal element (22) in which only the waves of the beam (Fp) form the local source (23) and the waves of the reference beam (F'2) create a sufficiently stable grating of refractive indices, the local oscillator being obtained by deflection of the waves of the beam (Fp) by this index grating before being mixed with the waves of the useful beam (F'2) in a detector (28) in order to form the beat signal. A processing suite (29) makes it possible, by modulation, to gain access to the information transported by the useful beam (F'2). Application to communication in free space, between two stations in relative movement. <IMAGE> |
