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Optical Engineering

Photonic security system using spatial codes and remote coded coherent optical communications
Author(s): Nabeel A. Riza; Mostofa M. K. Howlader; Nicholas Madamopoulos
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Paper Abstract

A novel photonic security system is described using 2-D spatial codes based on both optical phase and amplitude information. This security system consists of an optical interferometric encoding subsystem that rapidly reads and encodes the 2-D complex-valued spatial code, forming a wideband frequency modulated optical beam and a colinear optical reference beam. After appropriate coherence coding of this beam pair, the light is launched into a low probability of intercept communication channel such as an optical fiber or a narrow beamwidth free-space optical link. At the remote code receiving and data processing site, the received light beam pair is first coherently decoded. Then, a high speed photodetector via optical heterodyne detection generates an encoded wideband radio frequency signal that contains the original 2-D code. Decoding is implemented in parallel via two independent systems. One decoder uses a Fourier transforming lens to reconstruct an electronic image interferogram of the complex-valued user code. This image interferogram is sent to a high speed electronic image processor for verification purposes. The other decoder is a high speed coherent acousto-optic time integrating correlator that optically determines matchmismatch between the received encoded signal and the code signal generated by the electronic database. Improved security to the overall communication network is added by using various keycodes such as a time varying keycode that determines the exact spatial beam scanning sequence required for both proper encoding and decoding of the 2-D code information. This paper describes preliminary experiments using a simple 1-D amplitude modulated spatial code.

Paper Details

Date Published: 1 September 1996
PDF: 12 pages
Opt. Eng. 35(9) doi: 10.1117/1.600853
Published in: Optical Engineering Volume 35, Issue 9
Show Author Affiliations
Nabeel A. Riza, CREOL/Univ. of Central Florida (United States)
Mostofa M. K. Howlader, CREOL/Univ. of Central Florida (United States)
Nicholas Madamopoulos, CREOL/Univ. of Central Florida (United States)

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