Optical measurement by a dual-frequency comb based on Rayleigh scattered Stokes light

Abstract The backward stimulated Brillouin scattering in the optical fiber leads to a forward peaked Rayleigh scattering light with the same frequency shift. A dual-frequency comb is proposed and experimentally demonstrated, in which the frequency difference is equal to the Brillouin frequency shift. Further, a temperature measurement scheme is design based on the novel dual-frequency comb, where the radio-frequency (RF) signal is directly detected; neither high frequency photo detector or extra Mach–Zehnder interferometer (MZI) structure is required. The beaten RF signal is of narrower linewidth because the related phases are reduced, which enhances the measurement with a higher resolution. The measurement structured is demonstrated, in which the sensitivity of temperature measurement is 1.08  MHz ∕ ∘ C , same as the MZI structure, while the resolution is improved to 4.5 times compared to the traditional structure in the experiment.