The light propagation along a long positive column has been observed in a cold cathode fluorescent lamp. The optical signals are observed with the DC and AC voltage power during lamp operation. The light propagating is observed in the operation with the DC-rippled voltage as well as the AC-voltage. The optical signals propagate from the high voltage side to the ground. These signals show two kinds of features according to the before and after Townsend breakdown. At the dark current before Townsend breakdown, the optical intensity is damped and the propagation velocity is $10^4{sim}10^5m/s$. At the high current of normal glow after Townsend breakdown, the propagation velocity is 1$10^5{sim}10^6m/s$ without damping.