在背向抽运的光纤拉曼放大器(FRA)中,能够观察到级联的受激布里渊散射(SBS)。在SBS实验中，采用最大输出功率为3000 mW的三波长光纤拉曼激光器作为拉曼抽运源，25 km单模光纤(SMF)作为布里渊增益和拉曼增益介质，功率为3 dBm的外腔式激光器（ECL）作为布里渊抽运源。在实验中观察到的前、后向级联SBS的最高级数分别为156条和89条，前、后向SBS相邻级次光谱之间的频移分别为11 GHz和22 GHz，即它们波长间隔分别为0.085 nm和0.166 nm，光谱带宽分别为13.580 nm和14.812 nm。与前向传输相比，后向输出的平坦性要好。与单波长FRA相比，用三波长拉曼激光器作为抽运源更容易得到平坦性好和阶数更多的级联SBS。

In backward pumped fiber Raman amplifier (FRA), cascaded stimulated Brillouin scattering (SBS) is observed. In the experiment, a three-wavelength Raman fiber laser whose maximum output is 3000 mW was used as Raman pump, and 25 km single mode fiber (SMF) is used as both Brillouin and Raman gain media, an external cavity laser (ECL) whose power is 3 dBm is used as Brillouin pump. The backward cascaded SBS of 89 orders and forward cascaded SBS of 156 orders are observed. The frequency shifts of the backward and forward SBS between adjacent order are 22 GHz and 11 GHz respectively, namely their wavelength intervals are 0.166 nm and 0.085 nm respectively. The spectral bandwidths of the backward and forward SBS are 14.812 nm and 13.580 nm respectively. The flatness of backward spectral lines is better than that of forward. Compared with single-wavelength FRA, the three-wavelength Raman fiber laser used as Raman pump is easier to generate cascaded SBS.