Communication system and communication method using the same

Details Communication system and communication method using the same Communication system and communication method using the same

2011-07-05

2011-07-05

Vanderpuye, Ken N (Department: 2613)

Optical communications

Transmitter and receiver system

Including polarization

C380S277000, C380S278000, C385S001000, C385S002000, C385S003000, C385S011000, C385S024000, C398S140000, C359S485050, C359S506000

Reexamination Certificate

active

07974540

ABSTRACT:
A communication system capable of employing polarization-dependent phase modulators with a reversing configuration that preserves security against disturbance of a polarization state at a transmission path but without using Faraday mirrors and a communication method using the same are provided.A quantum cryptography system of the present invention includes a first station1,a transmission path2,and a second station3. The first station1has means for emitting time-divided optical pulses into the transmission path2and measuring a phase difference between the optical pulses returning from the transmission path2. The transmission path2is a medium of light. The second station3has means for reversing traveling directions of the optical pulses, means for producing a phase difference, corresponding to a random number bit value to be transmitted, between the time-divided optical pulses, means for splitting the entering optical pulse into orthogonally polarized components and producing a 180-degree phase difference therebetween, means for rotating each polarization direction by 90 degrees, means for eliminating a component resulting from a deviation from the polarization rotation angle of 90 degrees, and means for attenuating optical pulse intensity to include no more than 1 photon per bit.

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