全光逻辑信号处理是光通信网络中的关键技术，对于实现全光网络具有重要意义。基于周期性极化铌酸锂(PPLN)波导的和频效应+差频效应，在准相位匹配条件下，采用波导级联的方式设计并实现了全光数值比较器。通过数值计算和仿真得到波形图，并通过讨论眼图、脉冲宽度、消光比以及峰值功率延迟时间等指标分析了全光数值比较器的性能。结果表明，采用波导级联的方法对信号光进行处理，不仅可以完成相应的逻辑功能，而且可以保证信号的传输质量，还扩展了PPLN波导在全光逻辑信号处理方面的应用。

All-optical logic signal processing is a key technology in optical communication network, which has the potential to realize all-optical network. The all-optical numeric comparator is proposed based on Sum-Frequency Generation and Difference-Frequency Generation (SFG+DFG) in quasi-phase-matched cascaded Periodically Poled Lithium Niobate (PPLN) waveguides. The waveforms are obtained by numerical calculation and simulation, and the performance of all-optical numeric comparator is analyzed by the parameters such as eye diagrams, pulse width, extinction ratio and peak power delay time. The results show that the cascaded waveguides can be used to deal with the all-optical signal. It can realize the corresponding logic function and guarantee the transmission quality of the signal, which expand the capability of PPLN waveguide on the all-optical logic signal processing.