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通过芯径渐缩（指数型连续渐缩或阶梯型离散渐缩）的方法，可获得色散随距离下降的光纤，能补偿光纤损耗对孤子传输的影响．但芯径的连续变化，将导致模耦合．分析发现，在连续渐缩光纤中，即使Ｖ＞２４０４８始终满足，但仍可存在两种模式：①Ｚ→∞的稳态模；②兼有导模和辐射模部分性质的“过渡模”．过滤模的模式场是一系列ＬＰ′０ｍ的模式场的迭加，它包括导模ＬＰ′０１的模式场的辐射模ＬＰ′０ｍ（ｍ≥２）的模式场，其中随着ｒ→∞不是迅速衰减而是振荡着缓慢衰减．过渡模具有与激励模相同的传输常数，但幅度却以芯径渐缩的速率衰减．尽管指数型渐缩光纤可增加孤子的传输距离，但“过滤模”的影响始终存在．本文最后给出了在高斯近似下的过渡模和稳态模的功率计算公式
Through the method of core-diameter taper (exponential continuous tapering or step-type discrete tapering), the optical fiber with dispersion decreasing with distance can be obtained, which can compensate the influence of fiber loss on the soliton transmission. However, continuous changes in core diameter will result in mode coupling. It is found that there are still two modes in continuous tapered fiber: V> 24048, but there are two modes: (1) Steady-state mode of Z → ∞; (2) . The mode field of the filter mode is the superposition of a series of mode fields of LP’0m which include the mode field of the radiation mode LP’0m (m≥2) of the mode field of the guide mode LP’01, where r Decay quickly but oscillate with slow decay. The transitional mold has the same transfer constant as the excitation mode, but the amplitude decays at a rate that the core diameter tapers. Although exponential tapered fiber can increase the soliton’s transmission distance, the influence of “filter mode” always exists. At the end of this paper, we give the formulas for calculating the power of transitional mode and steady-state mode in Gaussian approximation