从波动理论出发,对锥形光纤的纵向传播常数进行泰勒(Taylor)级数展开,经近似得到了锥形光纤功率分布的解。基于此理论,对锥形光纤的功率分布特性进行了讨论,并分析了锥形光纤的长度、锥度和光纤折射率等参数对锥形光纤不同模式功率分布的影响。为了减小功率泄漏,当光从锥形光纤大端入射时,应当减小锥长,减小锥度,增大纤芯包层折射率差; 当光从锥形光纤小端入射时,应当增加锥长,增加锥度,增大纤芯包层折射率差。在长锥长、大锥度情况下,光纤折射率分布的影响相对较小。

The power distribution of the tapered fiber has been investigated based on Maxwell’s equation and the Taylor series expansion method. Following rigorous analytical approach, the general expressions for power in the core are derived, and a study is presented for the power distribution along the propagation direction in respect of different lower order modes. It is observed that the variation of the taper length, taper ratio, and refractive index can influence the power distribution of different fiber modes dramatically. The leakage loss, the taper length, taper ratio should be decreased. And refractive index difference should be increased if the light is launched from the smaller core-size end. And the taper length, taper ratio and refractive index difference should be increased if the light is launched from the larger core-size end to confine the power efficiently. When the fiber has long length and large taper ratio, the influence of refractive index on the power distribution is small compared with those of taper length and taper ratio.