  We report a continuous variable key distribution system that achieves a final
secure key rate of 3.45 kb/sec over a distance of 24.2 km of optical fiber. The
protocol uses discrete signaling and post-selection to improve reconciliation
speed and quantifies security by means of quantum state tomography.
Polarization multiplexing and a frequency translation scheme permit
transmission of a continuous wave local oscillator and suppression of noise
from guided acoustic wave Brillouin scattering by more than 27 dB.
