US Government As Represented by the Secretary of the Army

Westinghouse Electric Corporation

United States of America As Represented by the Secretary of the Air Force

Irwin J Abramovitz

Norman J Berg

Michael W Casseday

John N Lee

Robert L Miler

An apparatus including a first light modulator for modulating a first light beam with a signal, a second light modulator for modulating a second light beam with a reference signal, first lens means, positioned in an optical path of the second light beam, for introducing into the second light beam horizontal magnification/demagnification which gradually varies with respect to a vertical direction, a beam combiner for combining the first and second light beams, and photodetecting means for detecting the combined light beam received from the beam combiner. The apparatus, thus constructed, is capable of processing the 50 to 100 billion operations per second required for true Doppler (time compression/expansion) processing of SONAR signals.

Optical correlator and method of using same

Apparatus for processing data packets within a grid-based mesh network having a plurality of particular nodes at the intersections of rows and columns of data transmission links which link the nodes together, which apparatus can determine if a particular incoming data packet has previously been re-transmitted through a particular node or has a wavelength of a data packet currently being processed through the node and, a plurality of tunable filters for blocking a data packet from being re-transmitted if the packet has such a wavelength or was previously re-transmitted through the nodes.

Node for grid type single mode fiber optic local area network using

An optical acoustic charge transport (ACT) device provides a variable and continuous delay for RF signals. Received RF signals are converted to light and focused onto an optical ACT device. The continous delay is utilized to generate a false radar return.

False return signal apparatus

A controller at each node of a mesh type grid network of single mode optical fibers implements a switching algorithm which passes a given message to four neighboring nodes only once to avoid flooding the network. If a given wavelength is present on more than one input, the first to arrive is passed and the second to arrive is blocked. The network is configured to provide a large number of redundant paths, ensuring a high probability that a path will exist even in the face of significant network damage.

Node for grid type single mode fiber optic local area network

An acousto-optic diffraction and signal mixing device. A laser light beam is expanded and shaped into a sheet beam which is directed across the surface of an acousto-optic medium. Four acoustic transducers are disposed on the acousto-optic medium, two at each end of the medium. Each acoustic transducer is supplied with a signal to be propagated on the surface of the acousto-optic medium. The first two signals diffract the sheet beam to produce a first product diffracted beam of light containing the product of the first two signals. The second two signals diffract the sheet beam to produce a second product diffracted beam of light containing the product of the second two signals.

Acousto-optic diffraction and signal mixing device

A compact beam splitter apparatus for use with a surface wave acousto-optic time integrating correlator, including a beam splitter for splitting a laser light beam into two beams and a Koesters prism disposed in the paths of the two beams for folding a portion of each beam so that the two folded beam portions converge to a common beam position at a predetermined acute angle between the two beam portions. A single Koesters prism may be used as the beam splitter and the beam folding device, with two mirrors being used to reflect the two beams back to the Koesters prism.

Compact beam splitter for acousto-optic correlator

A device for processing signals to obtain a multi-product, time integrated, correlated output signal. A laser light beam is expanded and shaped into a sheet beam which is directed across the surface of an acousto-optic medium. Four acoustic transducers are disposed on the acousto-optic medium, two at each end of the medium. Each acoustic transducer is supplied with a signal to be propagated on the surface of the acousto-optic medium. The first two signals diffract the sheet beam to produce a first, product diffracted beam of light containing the product of the first two signals. The second two signals diffract the sheet beam to produce a second product diffracted beam of light containing the product of the second two signals. The two product diffracted beams are rotated so that they are orthogonal to each other, and then combined. A time integrating photodetecting means is disposed in the path of the combined beam for generating a multi-product, time integrated, correlated output signal.

Multi-product acousto-optic time integrating correlator

A method and device for processing spread-spectrum and other wideband comications and radar signals to obtain three and four product correlated signals. A laser beam is split and shaped into first and second sheet beams. The first beam is directed to a first acousto-optic medium where it is doubly diffracted by first and second signals. The second beam is directed to a second acousto-optic medium which is spatially rotated 90.degree. relative to the first acousto-optic medium where the second sheet beam is either singly diffracted by a third signal or doubly diffracted by a third signal and a fourth signal. The diffracted sheet beams are shaped into square beams, combined and directed to a photodiode area array.

Three and four product surface-wave acousto-optic time integrating

An acousto-optic time integrating two-dimensional frequency scanning correlator for cross-correlating signals which are separated in frequency. Two coherent light beams which are derived from the same laser are fed across respective Bragg cells, one cell having the signal A(t) cos .omega..sub.A t propagating thereacross and the other cell having the signal B(t) cos .omega..sub.B t propagating thereacross. The respective output beams are comprised in the x direction and expanded in the y direction and are made incident on an acousto-optical correlator device having chirp signals counter-propagating thereacross. The optical output is fed to a time-integrating photodiode array which provides an output signal corresponding to the cross-correlation of A(t) and B(t). In a further embodiment, the two Bragg cells are replaced by a single Bragg cell and beams having different polarizations are fed thereacross. In a still further embodiment, only a single crystal is used which has the A(t) and B(t) signals, as well as the chirp signals, counter-propagating thereacross.

Acousto-optic time integrating frequency scanning correlator

A highly efficient time integrating acousto-optic correlator which determs the time difference of arrival of the signals being correlated as well as the center frequency and bandwidth of the signals. A surface acoustic wave delay line is provided with two counter-propagating surface acoustic waves with wavefronts tilted with respect to each other. Two laser beams are directed across the propagating waves with an angle of 4.theta..sub..beta. between them where .theta..sub..beta. is the Bragg angle, so that one beam interacts primarily with one propagating wave while the other beam interacts primarily with the other wave. The modulated optical beams are directed to a time-integrating photodetector means which provides a signal output corresponding to the correlation function.

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Baltimore, MD, United States of America

Irwin J Abramovitz