短语词组短语rayleigh backscattering noise 瑞利散射噪声double rayleigh backscattering noise 双重瑞利散射噪声double Rayleigh backscattering 二次瑞利散射rayleigh backscattering light 瑞利散射光fiber Rayleigh backscattering 光纤瑞利散射 返回 rayleigh backscattering