Angle modulated transmitted reference heterodyne laser communication system is insensitive to atmospherically induced amplitude noise fluctuations and phase distortions

Packard, J. N.

English

NASA Technical Reports Server

December 1967	 Brief 67-10587 
•	 NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Laser Communication System Is Insensitive to Atmospherically induced Noise 
Signal Laser I	 I Photomultiplier
II Received 
Telescope	
B am 
Generatorh..1	 Amplifier	 f_._IModulator_Driven_s.]	
Pockels	 I 
Modulator
	
	
Converter
Transmitteditted Beam 
	
1fl--	 _Ii1nAr 
	
Beam Combiner	 I	 Limiter 
CR0	 -s.I	 Amplifier	 1-4 Discriminator 
	
TRANSMITTER	 RECEIVER 
The problem: 
To develop an optical communication system that is 
insensitive to atmospherically induced amplitude 
noise fluctuations and phase distortions. 
The solution: 
An angle modulated transmitted reference hetero-
dyne laser communication system. The block diagram 
shows an implementation of the system for single-
frequency subcarrier modulation. 
How it's done: 
The modulation waveform (intelligence) derived 
from the signal generator, is amplified and applied 
to a Pockels cell modulator (using a 45° Y-cut ADP 
crystal) that phase modulates the signal laser beam in 
synchronism with the modulation waveform. The sig-
nal beam laser and reference beam laser are tuned,
servo-locked, and stabilized to a difference frequency 
of 300 MHz. The beams are collimated, combined, 
and transmitted through the atmosphere to the re-
ceiver. At the receiver, the beam through the tele-
scope is focused on a photomultiplier detector and 
the difference frequency is generated. The 300 MHz 
difference signal is amplified, converted to a 60 MHz 
second IF, amplified, limited, and discriminated to 
recover the modulation waveform which is amplified 
and displayed on a cathode ray oscilloscope. 
Note: 
Inquiries concerning the design and characteristics 
of this system may be directed to: 
Technology Utilization Officer 
Goddard Space Flight Center 
Greenbelt, Maryland 20771 
Reference: B67-10587
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19670000586 2020-03-11T21:31:57+00:00Z
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546.
Source: John N. Packard 
of Aircraft Armaments, Inc.
under contract to

Goddard Space Flight Center 
(XGS- 10396) 
Brief 67-10587	 Category 01


Laser communication system is insensitive to atmospherically induced noise

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