SECURE COMMUNICATIONS SYSTEM

Abstract

There is provided by this invention a secure fiber optic communication system based on the Sagnac interferometer that allows multiple authorized users to communicate on the system by modulation and detection of two counterpropagating light beams. The security of the system is based on a combination of the information being modulated on the relative phase difference between the counterpropagating light beams and the low coherence length of the light source. In order for an intruder to intercept the signal, both counterpropagating beams must be accessed and the pathlength of the two beams matched to within a few coherence lengths of the light source so that an amplitude modulated output signal may be constructed. The system is further comprised of a random pathlength generator used to randomly vary the relative pathlength of the two counterpropagating beams. A light level alarm is provided that detects changes in the light level within the system. If the signal level changes sufficiently, the light level alarm shuts down the system.

Source: Google Patents

35 USC §181 Secrecy Order

Inventor

• 1ERIC UDD

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