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根据非线性薛定谔方程建立了基于可饱和吸收体被动锁模掺Er3+氟化物光纤激光器的理论模型,研究了中红外超短脉冲在掺Er3+氟化物光纤激光器中形成的物理机制,数值模拟了被动锁模掺Er3+氟化物光纤激光器中中红外超短脉冲的演化过程,重点分析了掺Er3+增益光纤长度,可饱和吸收体不饱和损耗对被动锁模掺Er3+氟化物光纤激光器产生中红外超短脉冲的影响,并给出了参数设置范围.研究发现:当小信号增益系数、可饱和吸收体不饱和损耗、腔内净色散量为一定值,掺Er3+氟化物光纤长度在一定范围时,才会出现稳定的锁模脉冲,且随着掺Er3+氟化物光纤长度增加脉冲宽度变窄、光谱变宽、峰值功率增高;当掺Er3+氟化物光纤长度、腔内净色散量、小信号增益系数为一定值时,可饱和吸收体不饱和损耗在一定的范围时可以得到稳定的锁模脉冲,且随着可饱和吸收体不饱和损耗的增加脉冲宽度变窄,光谱先变宽后变窄变化范围不大,峰值功率增加.“,”Based on the Nonlinear Schr?dinger Equation(NLSE), the theoretical model of psssively mode-locked Er3+-doped fluorid fiber laser using a saturable absorber was set up, by which the mechanism of generating mid-infrared ultrashort pulse in the fiber laser was investigated. The numerical simulation focused on the evolution process of the mid-infrared ultrashort pulse in fluorine fiber laser. The impact of the Er3+: fluorine gain fiber length and the saturable absorber unsaturated loss on the generation of mode-locked pulse was analyzed in detail, and the reasonable parameter range was determined. It is found that for a given set of small-signal gain, unsaturated loss, and net intracavity dispersion, the stable mode-locked pulses are achieved by tuning the Er3+: fluorine gain fiber length within a certain range. With increasing the Er3+: fluorine gain fiber length, the output pulse duration decreased gradually, while the increase of the spectrum width (FWHM) and the peak power are observed. Meanwhile, for a given set of Er3+: fluorine gain fiber length, net intracavity dispersion and small-signal gain, the stable mode-locked pulses are also obtained by adjusting the saturable absorber unsaturated loss within a certain range. With the increase of the saturable absorber unsaturated loss, the output pulse duration decreases gradually, however spectral width broadens and then narrows, and peak power increases gradually.