We have developed the fiber optic probe method to monitor the ablation bubbles previously. The backscattered light of the probe laser from the ablation area was monitored through the same fiber of which the Ho:YAG laser pulse was delivered. This method may become available in vivo. We measured the decay time of the backscattered light waveform. The theoretically explanation showed that the calculated bubble collapse time approximately coincided with the decay time of waveform. Since the ablation bubble collapse is strongly affected by mechanical properties of its adjacent tissues, the decay time suggested their surrounding tissue types. We demonstrated the possibility of the tissue characterization by this probe method. In order to know the characteristic of the observed backscattered light to understand our probe method capability for tissue characterization, we performed comparative measurements for the ablation bubble by means of time-resolved photography and the probe method.