建立了双包层光纤光学放电现象的理论模型，并对其进行了数值模拟。结果表明双包层光纤放电传输速度随功率密度增加而非线性增加。当功率密度较大时，速度增加较为缓慢。光学放电的功率密度阈值与初始加热温度有关，当加热温度一定时，功率密度阈值随芯径增大而减小。从实验上比较了不同芯径双包层光纤的光学放电阈值，实验结果与模型结论符合较好。比较了芯径相同、内包层直径不同的光纤的放电传输速度与功率密度的关系。结果表明内包层直径较大的光纤放电传输阈值略高，但传输速度与功率密度的关系基本一致，说明芯径是影响放电传输速度的主要因素。

A model of describing optical discharge effect of double cladding fiber is proposed. The simulation results show that the velocity of optical discharge of double cladding fiber nonlinearly increases with the increase of power density in the fiber core and the velocity slowly increases at a higher power density. The threshold of optical discharge depends on the initial heated temperature. When the initial temperature is fixed, the threshold decreases with the increase of the diameter of fiber core. The thresholds of double cladding fiber with different core diameters are compared expenmentally, which are consistent with the model. Moreover, the comprison of different inner cladding diameters with the same core diameter shows that the threshold of larger inner cladding fiber is relatively high while the relationship between propagation velocity and power density is the same, which indicates that the core diameter is the main factor affecting optical discharge velocity.