| 摘要 |
<p>PCT No. PCT/GB91/01352 Sec. 371 Date Feb. 18, 1993 Sec. 102(e) Date Feb. 18, 1993 PCT Filed Aug. 8, 1991 PCT Pub. No. WO92/04785 PCT Pub. Date Mar. 19, 1992.An optical communications system (10) comprises a transmitter (12) and a receiver (14). A source (16) of correlated pairs of photons of conjugate energies provides first and second photon beams (38, 36). The first photon beam (38) passes through a modulated filter (50) to which a communications signal (52) is applied. A variable spectrum beam (54) is produced which is converted to a timing signal (68) of macroscopic optical pulses (66). The second photon beam (36) and timing signal (68) are transmitted to the receiver (14). The received timing signal (84) is converted to a series of electrical timing pulses (90). The received second photon beam (82) passes through an unmodulated filter (94) matched to the modulated filter (50) when the signal (52) is not applied. The unmodulated filter splits the beam (82) into two conjugate spectra photon beams (96, 98) which are then converted to first and second series of electrical pulses (108, 110) respectively. The pulses (90, 108, 110) enter a coincidence counter (92) which records coincidences between the timing pulses (90) and the first series of pulses (108) and between the timing pulses (90) and the second series of pulses (110). Two coincidence rates are obtained and subtraction of one from the other yields an output communications signal (112).</p> |
