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Dependences of Brillouin frequency shift on strain and temperature in optical fibers doped with rare-earth ions

Brillouin scattering properties in rare-earth-doped fibers, including Nd3+-doped, Tm3+-doped, Sm3+-doped, and Ho3+/Tm3+ co-doped fibers, can potentially be controlled at high speed by pumping, but there has been no report on their detailed investigations. In this study, the Brillouin gain spectra (BGS) in such rare-earth-doped single-mode fibers are measured, for the first time to the best of our knowledge, at 1.55 μm without pumping, and the Brillouin frequency shift (BFS) and its dependences on strain and temperature are investigated. Clear BGS was observed for the Nd3+-doped and Tm3+-doped fibers, but BGS was not detected for the Sm3+-doped and Ho3+/Tm3+ co-doped fibers probably because of their extremely high propagation losses at 1.55 μm and small Brillouin gain coefficients. The BFS of the Nd3+-doped fiber was ~10.82 GHz, and its strain and temperature coefficients were 466 MHz/% and 0.726 MHz/K, respectively. As for the Tm3+-doped fiber, the BFS was ~10.90 GHz, and its strain and temperature coefficients were 433 MHz/% and 0.903 MHz/K, respectively. These measurement results are compared with those of silica fibers.