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Distributed Brillouin-based optical fiber sensors are of a great interest for the monitoring of strain and temperature distributions within large structures in civil engineering. Injection locking of two DFB semiconductor lasers is a simple and rather universal technique that allows generation of low-noise coherent signals (AM, FM, frequency-shifted or frequency sweeping optical waveforms) relevant for operation with different Brillouin sensors. The accuracy of such sensors among other factors is limited by the Stokes intensity noise dominating in MHz-frequency range. Here we report on specific features of the Stokes intensity noise revealed with a configuration that involves injection-locking for generation of the Stokes signal.