COHERENT OPTICAL ADAPTIVE TECHNIQUES.
Abstract
A system was designed, constructed and tested which provides dynamic adaptive phase compensation for atmospheric distortions. This demonstrates that arrays can be built larger than previously thought possible because of atmospheric effects. Without adaptive controls, the atmosphere limits the signal-to-noise ratio improvement and the beamwidth reduction which can be obtained using a larger transmit-receive aperture. We accomplished phase compensation for the transmitted beams and the received signals of a two-element 10.6 micron array. By providing adaptive phase control to assure that the two transmitted beams arrived at the target in phase, the power on target was increased by at least 75 percent over the nonadapted case. In addition, the amplitude fluctuations of the received signals were drastically reduced because the adaptive transmitting system eliminated the frequent destructive interference normally seen when two beams are transmitted. Adaptive control of the relative phase of the two received signals before adding also resulted in comparable increases in signal power. The locking of two lasers with a 4.5 MHz difference frequency provided the local oscillator for heterodyne detection. A near target 500 feet and a far target 3 miles from the transmitter were used. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1968
- Accession Number
- AD0837611
Entities
People
- Cecil L. Hayes
- Wade T. Cathey
- Walter C. Davis