Unconditionally secure quantum key distribution with relatively strong signal pulse

We propose an unconditionally secure quantum key distribution protocol, which uses a relatively strong signal pulse. While our protocol shares similar security bases as the Bennett 1992 protocol with a strong reference pulse, our scheme uses a smaller number of detectors and it is robust against Rayleigh scattering in an optical fiber. We derive a lower bound of secret key generation rate of our protocol and show that our protocol can cover relatively long distances, assuming precise phase modulations and stable interferometers.