OTDR based on Brillouin dynamic grating in an e-core two-mode fiber for simultaneous measurement of strain and temperature distribution

Discriminative measurement of strain and temperature distribution is experimentally demonstrated by optical time-domain reflectometry of Brillouin dynamic grating (BDG-OTDR) in an elliptical core two-mode fiber (e-core TMF). The acoustic waves generated by the amplified spontaneous Brillouin scattering of LP01 mode in x-polarization are used to reflect the LP11 mode in x-and y-polarizations. Distribution maps of intermodal birefringence between the LP01 and LP11 modes with two different polarizations are measured to separate strain and temperature induced spectral shift of the BDG in a 95 m e-core TMF with 2.0 m spatial resolution. The strain and temperature sensitivities are measured to be -0.082 MHz/mu epsilon and 6.8 MHz/degrees C for the pair of LP01y-LP11x modes, and -0.095 MHz/mu epsilon and 3.9 MHz/degrees C for the pair of LP01x-LP11x modes, respectively.