Optical Signal Processing.
Final rept. 1 Oct 80-30 Sep 83,
HARRIS CORP MELBOURNE FL GOVERNMENT SYSTEMS SECTOR
Pagination or Media Count:
An interferometric spectrum analyzer technique, using a distributed local oscillator, doubles the dyamic range of a conventional power spectrum analyzer i.e., 60 dB vs. 30 dB, has an instantaneous analysis bandwidth of 200-1000 MHz, and is immune to scattered noise. An analysis of Bragg cell diffraction patterns shows that acoustic spreading leads to a curvature of the diffraction pattern along an elliptical or parabolic loci. Bounds on the size of integrating photodetector along the curved direction have been established based on frequency resolution criterion. This activity was extended to correct the acoustic spreading by using a holographic element. For a 12-channel Bragg cell operating over an 80 MHz bandwidth, the usable aperture was increased from 10 to 100 the number of channels increased by a factor of four. An adaptive optical processing technique has been developed to overcome the bandwidth limitations of digital systems. These Bragg cells, used in an interferometer, provide the signal to be convolved as well as the tap weights. Extensive computer simulations of the performance of the system, given the finite integration times imposed by the Bragg cells, show that notch depths of 30-40 dB can be achieved for a system having at time-bandwidth product of 2000. Author