No abstract

Doppler velocimeters for remote velocity sensing require a compact and miniaturized system. We report the achievement of an eye-safe Doppler velocimeter at 1.54microm using InGaAsP diodes reduced in linewidth by external cavity stabilization techniques. Linewidth of the diodes was of the order of 40 kHz allowing for a sub-cm/s velocity resolution over long distances (i.e., 100 m).

A coherent CO(2) laser communication system that yields high-quality voice communications between a transmit-receive station and a remote site (24 km) where modulable retroreflectors are located was developed. The potential range capability of this system was 80 km, and the system was improved by 20 dB in the signal-to-noise ratio over a direct-detection system.

A CO(2) laser Doppler detection system has been developed to measure remotely the true airspeed of an aircraft. The system uses a 50-W sealed-off CO(2) laser in a homodyne detection system employing a collinear optical telescope, a HgCdTe detector, and a frequency tracking loop. The system was successfully flight tested on a NASA Convair 990 research aircraft during December 1971 and June 1972. The results indicate that an airspeed measurement under clear weather conditions is feasible up to an altitude of 3000 m with an error of less than 0.5%.

A 10.6-micro optical heterodyne communication system is described that uses two stable single mode and single frequency CO(2) lasers of high frequency stability. Wavelength control on both lasers allows the use of one and the same transition of the rotation-vibration band of CO(2) around 10.6 micro. The system has a bandwidth of 1 MHz, and simultaneous operation in baseband and on a 50-kHz carrier has been achieved. Heterodyne detection with mercury cadmium telluride detectors yielded signal-to-noise ratios within 3 dB of the coherent photon noise limit.