| 摘要 |
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 con- verted to a timing signal (68) of macroscopic optical pulses (66). The secon d photon beam (36) and timing signal (68) are trans- mitted to the receiver (14). The received timing signal (84) is converted to a series of electrical timing pulses (90). The received sec- ond photon beam (82) passes through an unmodulated filter (94) matched to th e 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 seri es of pulses (108) and between the timing pulses (90) and the second series of pulses (110). Two coincidence rates are obtained an d subtraction of one from the other yields an output communications signal (112).
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