短语词组短語rayleigh backscattering noise 瑞利散射噪聲double rayleigh backscattering noise 雙重瑞利散射噪聲double Rayleigh backscattering 二次瑞利散射rayleigh backscattering light 瑞利散射光fiber Rayleigh backscattering 光纖瑞利散射 返回 rayleigh backscattering