Dynamic or static strain sensing and signal demodulation are realized by using random non-uniform sampling of superimposed fiber Bragg gratings (FBGs). Superimposed FBGs demodulating system based on tunable filter and its realization of non-uniform sampling method are presented. The superimposed FBGs are designed to generate non-equidistant space of sensing pulse train in time domain during dynamic strain signals measurement. By combining centroid hardware finding algorithm with smooth filtering method, the demodulation speed and accuracy can be simultaneously kept. Random non-uniform sampling of superimposed FBGs can be realized by generating periodic random variable triangle wave driving voltage of tunable filter. By using superimposed FBGs, a 1.9 kHz dynamic strain is measured by generating an additive non-uniform random distributed 2 kHz optical sensing pulse train at a triangular wave periodically randomly changing scanning voltage with the mean scanning frequency of 500 Hz. The dynamic strain measurement bandwidth is eight times of single FBG interrogation system.