Frequency domain staring pump-probe technique for Brillouin gain/loss spectrum measurement.

We propose and demonstrate a modified frequency sweep-free pump-probe technique, called staring pump-probe technique (SPPT) for Brillouin signal measurement based on stimulated Brillouin scattering (SBS). The SPPT retains the advantages of conventional pump-probe technique, and employs a simple device and low-cost measurement system. Moreover, the Brillouin gain/loss spectrum (BGS/BLS) can be reconstructed without frequency-sweep, thus greatly improving the measurement speed. In this paper, an approximate flat-top spectrum broadened probe light is introduced through distributed feedback laser by direct modulation. The BGS/BLS is reconstructed with the enhanced signal-noise ratio of approximately 21 dB/23 dB. This technique has a potential application for some Brillouin scattering involved Brillouin frequency shift measurement.