Essex Corporation

Northrop Grumman Systems Corporation

James L Lafuse

Terry M Turpin

Gerald Joseph Davieau

Paul W Woodford

Leslie H Gesell

Keith R Frampton

Craig H Price

Bruce D Nichols

Fred F Froelich

Gerald Davieau

An optical code division multiple access communication system using a processor processes at least one collimated input beam which has been modulated with a data signal to produce multiple time-delayed output beams. The multiple time-delayed output beams are spatially distributed and independently phase shifted. An integration lens receives the phase modulated output beams and reintegrates the phase modulated output beams into a single encoded beam with a time series chip sequence. The integrated encoded beam is transmitted. A receiving system includes a processor to process the encoded collimated light beams received from a transmitter to produce multiple time-delayed output beams. The multiple time-delayed output beams are spatially distributed and independently phase shifted. An integration lens receives the phase-shifted output beams and reintegrates the phase-shifted output beams into a single decoded beam.

Optical CDMA communications system using OTDL device

An Optical Tapped Delay Line (OTDL), which resolves multiple wavelength signals having extremely narrow wavelength spacing, is combined with other known optical devices to provide a wide variety of optical signal processing applications, including: multiplexing and de-multiplexing a multi-channel signal; adding a signal to, or dropping a signal from, a multi-channel optical signal; specialized coding processing such as generating code division multiple access signals; wavelength locking (stabilizing) a signal; filtering a signal; and analyzing and monitoring a signal spectrum. The OTDL spatially separates individual channels to allow separate processing on each channel. Fixed and tunable embodiments are identified in appropriate cases. Bulk, hybrid, and integrated optical embodiment and methods of fabrication are described, as are curved self-focusing and evanescent embodiments of OTDL devices. The devices and processes disclosed have particular application to dense wavelength division multiplexing (DWDM) and permit a significant improvement in the quantity of information that can be carried on DWDM signals while enhancing signal quality.

Method and apparatus for optical signal processing using an optical tapped delay line

Methods for mitigating sidelobes and aliases, providing levels of suppression in excess of 20 dB. The methods may include 1) a version of the CLEAN algorithm developed in radio astronomy, modified to work on sub-aperture images; 2) weighting functions based on the phase and amplitude statistics of the sub-aperture image pixels to select points in the CLEAN algorithm; and 3) weighting functions based on the phase and amplitude statistics of the sub-aperture image pixels to mitigate sidelobes and aliases, in conjunction with CLEAN or separately. The methods may be used with all synthetic aperture techniques and are not limited to SAR.

Sub-aperture sidelobe and alias mitigation techniques

A method and apparatus for enhancing the receiving and information identification functions of multiple access communications systems by employing one or more optical processors configured as a bank of 1-D correlators. The present invention is particularly useful in a DS/SS CDMA communications system, resulting in a multiuser CDMA system that approaches carrier to noise performance (C/N) as opposed to being limited by multiple access interference (MAI). The correlators are arranged in parallel to detect and/or demodulate the received signal, in conjunction with one or more complex algorithms to perform near-optimum multiuser detection, perform multipath combining and/or perform carrier Doppler compensation. An improved receiver in accordance with the present invention comprises means for receiving a plurality of signals transmitted through a communications channel; signal conversion means for converting the received signals into a form suitable for input to the multichannel correlator; a multichannel optical correlator for identifying the presence of particular waveforms and estimating the relative time delay or delays, carrier frequency offset from expected, RF amplitude and RF phase for each received spread spectrum waveform present in the received plurality of signals; a controller for determining and providing to the optical correlator the appropriate set of reference hypotheses; and one or more receiver algorithms depending on the exact receiver function to be performed.

Optical processor enhanced receiver architecture (opera)

Optical systems are disclosed which are capable of generating and rapidly changing time delays of electrical signals for true time delay beam formation and beam steering. The systems utilize an interferometer configuration. A first optical modulator and a Fourier transform lens define a Fourier transform plane in a first leg of the interferometer. In a second leg of the interferometer, a second optical modulator provides beam steering to a prism stack, which produces a set of plane reference waves having a range of orientations required to generate a desired range of time delays. Preferably the optical modulators are acousto optic Bragg cells. Alternatively, a holographic optic element could be used in place of the prism stack.

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Columbia, MD, United States of America

James L Lafuse