Fast distributed temperature sensing using Brillouin beat spectrum of large effective area fiber (LEAF)

We investigate the temperature dependence of the beat spectra of stimulated Brillouin scattering from a large effective area fiber (LEAF) in an Optical Time Domain Reflectometry (OTDR) configuration. The multiple gain peaks inherent to the design of this fiber undergo homodyning at the receiver and the amplitude of one of the beat tones is monitored as a function of temperature for a 4 km long fiber. Contrary to previous reports, the beat signal of the first two peaks is found to be decreasing with temperature. The above measurement is performed within 4 ms, thus opening the possibility of dynamic measurement of temperature and strain.