We demonstrate the first experimental investigation of the interaction
between black and gray solitons in an optical fiber. The fiber length
equals 8 soliton distances. The repulsive character of the interactio
n is observed during the walk-off of the gray soliton through the blac
k one inside the finite-width background carrier pulse. Opposite cases
of the gray soliton phase profile are studied, corresponding to gray
pulses with a group velocity higher and smaller than that of the carri
er pulse. Numerical simulations presented show good agreement with exp
erimental data.