SECURE COMMUNICATION SYSTEM

Assignee

MCDONNELL DOUGLAS CORPORATION, A CORP. OF MD

Filed

Nov 14, 1988

Granted

Mar 2, 1993

Location

BUENA PARK CA US

Abstract

There is provided by this invention a secure fiber optic communication system based on the Sagnac interferometer having features that make the system intrusion resistant. The security of the system is based on placing a random phase modulator at the midpoint of the communications loop that will phase modulate the counterpropagating light beams according to a string of random data to scramble the signal information. The detector for the system is located at the point of origination and recombination of the counterpropagating beams such that the scrambling signal cancels out at the point of detection allowing the intelligence signal to be demodulated without additional electronics. In order for an intruder to intercept the signal, both counterpropagating beams must be accessed at the transmitter which is in a controlled area. Intrusion at any other point in the loop will intercept the light signal which contains part of the scrambled data which is unintelligible.

Source: Google Patents