Characterization of Brillouin Gratings in Optical Fibers and Their Applications

There is an increasing interest over recent years in Brillouin gratings in optical fibers due to their applications in optical storage (Cao et al., 2008; Kalosha et al., 2008; Zhu et al., 2007), distributed sensing (Dong et al., 2009; Song et al., 2009, 2010; Zou et al., 2009a, 2009b, 2010), optical delay line (Song et al., 2009), and birefringence characterization of polarizationmaintaining fibers (Dong et al., 2010). Generally, a Brillouin grating is generated by using two counter-propagating pump waves through stimulated Brillouin scattering (Song et al., 2008). A Brillouin grating is formed by a moving periodically modulated refractive index associated with an acoustic wave, which is created by two pump waves through electrostriction effect. Compared with conventional fiber Bragg gratings, the Brillouin gratings have two unique features: one is that it is a moving grating, which can produce a Brillouin frequency shift on the reflected light with respect to the probe wave, and the other is that it has a lifetime (~10 ns in a silica fiber) for its existence after removing the two pump waves.