Optical: systems and elements – Optical modulator – Light wave temporal modulation
Patent
1989-05-15
1991-09-24
LaRoche, Eugene R.
Optical: systems and elements
Optical modulator
Light wave temporal modulation
359559, 359634, 359111, 359566, G02F 111, G02F 103, G02B 2742
Patent
active
050509675
ABSTRACT:
Nonlinear optical techniques are utilized to provide an adaptive notch filter for removing narrowband noise from broadband RF communication signals. The received RF signal is converted to a corresponding acoustic wave propagated in an acousto-optic cell. Two mutually coherent beams of light are passed through and diffracted by the acousto-optic cell. The diffracted beams are modulated by the acoustic wave, the second beam being modulated at a predetermined time delay with respect to the first beam. By proper selection of the time delay, the narrowband components of the two beams remain mutually coherent while the broadband components become mutually incoherent. The two diffracted beams are then mixed within a photorefractive crystal so that a first mixed beam comprises substantially all of the narrowband components while a second mixed beam consists essentially of only the broadband components. The second mixed beam is then detected and processed to filter out the time delay echo, leaving the useful broadband signal without the narrowband noise.
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LaRoche Eugene R.
Lester E. A.
McFarren John C.
Rockwell International Corporation
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