When the core radius is smaller, and the refractive index of absorbing medium is few different with refractive index of core,the modal power in the cladding will be higher and more energy react with absorbing medium.

• 纤芯半径越小,纤芯折射率与吸收介质折射率越接近时,模式包层中的功率百分比较大,有更多的能量与吸收介质相互作用。