  In this report, we simulate practical feature of Yuen-Kim protocol for
quantum key distribution with unconditional secure. In order to demonstrate
them experimentally by intensity modulation/direct detection(IMDD) optical
fiber communication system, we use simplified encoding scheme to guarantee
security for key information(1 or 0). That is, pairwise M-ary intensity
modulation scheme is employed. Furthermore, we give an experimental
implementation of YK protocol based on IMDD.
