对铌酸锂马赫-曾德调制器（MZ-LN）调制特性曲线、半波电压和零点电压进行了测量。实验表明调制特性曲线存在一定的偏移，调制器的零点电压存在严重的漂移现象。实验研究了零点漂移对NRZ码和DPSK信号的影响，指出零点漂移与调制器的残留电压有关，产生原因来自于内部结构存在的电荷储存效应。

Lithium niobate Mach-Zehnder modulator（MZ-LN）is one kind of waveguide-type optical modulators commonly used in optical communication. Based on introducing the principles and structure of MZ-LN, the performance curve of modulation, the half-wave voltage and the zero-point-voltage were measured. Experimental results demonstrate that the curve of half-wave voltage has offset voltage and the zero-point will drift during working. It was experimentally studied the impact of zero-point-drift on the NRZ code and DPSK signal. And it is indicated that one reason for zero-point-drift is the stored charge effects caused by the internal structure of modulator.