Simple distributed optical fiber sensor based on Brillouin amplification of microwave photonic signals

A simple distributed fiber sensor is proposed by Brillouin amplification and depletion of microwave photonic signals. This technique utilizes optical carrier suppression (OCS) modulation to generate two sidebands acting as the pump waves. After Fresnel reflection at the cleaved end of the fiber under test (FUT), the pump waves are converted to probe waves. By sweeping the modulated microwave frequency, the stimulated Brillouin scattering (SBS) spectra and Brillouin frequency shift (BFS) can be precisely characterized. As a result, the accurate measurement of the Brillouin frequency shift makes good determination of the distributed temperature or stain along the FUT, and the position along the FUT can be resolved and controlled by the delay of the microwave pulses. Furthermore, our proposed sensing system is implemented with a single-ended configuration which has shown many advantages such as immunity of the laser frequency fluctuation and compact setup without additional pump laser source and filters.