---

Revision with unchanged content. Quantum Cryptography enables secret distribution between remotes parties where classical communications fail. The proposed technique uses optical signal modulation to encode information with relative phase difference between frequency separated signals. The single side band detection scheme (SSB) enables efficient secret key distribution. The system security is guaranteed with a strong reference protocol. One can use a fainted laser source without security breach for any distance. A second proposed technique uses relative phase difference between time separated pulses. The single side pulse detection scheme (SSP) enables efficient secret key distribution and benefits the same security features as the SSB system. Both SSP and SSB may be multiplexed to increase the secure bit rate. The maximizing initial average energy is then one photon per pulse. The implemented SSB protocol includes an autocompensation system for the optical path fluctuations that make the system robust over long time periods.

---

Olivier L. Guerreau received the Diplôme d´lngénieur degree from Supélec, Paris, and the Master of Science degree from the Georgia Institute of Technology, Atlanta, both in 2001. He also received the Docteur ès Science degree from the University of Franche-Comté, France, in 2004 and a Ph.D. degree from Georgia Tech in 2005.

---