RECEIVERS FOR LASER RADARS
Interim engineering rept. no. 1, 15 Nov 1962 14 Feb 1963
HUGHES RESEARCH LABS MALIBU CA
Pagination or Media Count:
The objective of this work is to investigate theoretically and experimentally the properties of a laser preamplifier for an optical Doppler radar receiver. In order to ascertain the fundamental limitations of various methods of detecting or amplifying optical radiation, a comprehensive literature search was undertaken to include all important papers on the quantum theory of noise and quantum mechanical ampli fiers. For comparison of the various types of receivers, a particular method was chosen for describing the signal and calculating the un certainties introduced and was applied uniformly to all the different systems. The signal-to noise ratios of an optical signal were calculated after attentuation in a transmission medium and after amplification by four different systems a photodetector, a single mode laser amplifier, a single mode optical heterodyne, and a laser preamplifier followed by an optical heterodyne. It was found that an amplifier must be used be fore the signal becomes too weak average number of received photons approaches unity or infor mation will be irretrievably lost. If the system parameters indicate this will happen, a laser amplifier should be used in front of the trans mitter assuming the power handling capabilities are available.
- Lasers and Masers