We propose a frequency-sweep-free method for a SBS sensor, where the Brillouin shift is determined
without the need of sweeping the frequency of any of the optical waves. This is implemented by generating
simultaneous frequency tones in both probe and pump channels and by properly arranging their frequency
values. The closest tone to the Brillouin shift receives the most amplification, and thus the Brillouin gain
frequency center can be obtained from a single measurement. We experimentally demonstrate the feasibility
with CW probes and pumps. The extension to a fast sweep-free Brillouin optical time domain sensing is
performed through detailed simulations.