In this paper,an improved UWB Pulse Amplitude Modulation ( PAM) scheme based on cross-gain modulation ( XGM) in SOA is presented,and use the software of Optisystem7. 0 to simulate. The influence of source power,modulation rate and source wave-length on the PAM signal is firstly investigated,and the results show that by appropriately setting light source power and modulation rate, the scheme can generate better PAM signal and is not sensitive to light wavelength change. In addition,the transmission characteristics of PAM signal in the optical fiber are analyzed,and the results show that modulation signal in PAM formats is greatly influenced by the dis-persion and attenuation,and the transmission distance is short.%文中提出了一种基于半导体光放大器(SOA)中交叉增益调制(XGM)效应的超宽带(UWB)脉冲振幅调制(PAM)方案。并利用Optisystem7.0软件对其进行仿真。首先研究了超宽带PAM信号对光源功率、调制速率、光源波长的敏感度，结果表明该方案可以通过设置合适的光源功率和调制速率产生较好的PAM信号，并且对光源波长变化不敏感；另外分析了在光纤中PAM信号的传输特性，结果表明PAM格式的调制信号受色散和衰减影响较大，传输距离较短。
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