Plug and Play Systems for Quantum Cryptography

To compensate for all polarization fluctuations in the transmitting fiber by using Faraday mirror is discussed, and "plug- and- play" system based on Faraday mirror for quantum cryptography is introduced, phase-encoding analysis in brief for plug- and- play system is implemented. The interfering pulses follow exactly the same spatial path, ensuring very high stability and self-compensating. The use of Faraday mirrors compensates for automatically any birefringence effects and polarization dependent losses in the transmitting fiber.