光阈值器件是多用户光码分多址(OCDMA)系统接收机中抑制基底噪声和互相关旁瓣峰的重要部件。非线性光环镜(NOLM)是实现光阈值的一种有效方法。对基于高非线性光纤(HNLF)NOLM的阈值特性进行了实验研究及数据分析，提出利用改变抽运脉冲占空比分析阈值特性的方法，实验发现抽运脉冲占空比D为1/25时出现阈值点，阈值功率为3.75 W。讨论了抽运光与信号光的波长间隔对NOLM输出信号的影响，得出阈值点处的最优波长间隔为5.8 nm，脉冲压缩量为114.47 ps。实验搭建了接收机阈值系统，眼图分析表明该系统能较好地抑制噪声。

For suppressing pedestal and cross-correlation noises in receiver, optical thresholder plays an important role in multiple-user optical code-division multiple access (OCDMA) system. Nonlinear optical loop mirror (NOLM) is an effective method to implement optical thresholder. The threshold characteristic is experimentally demonstrated and analyzed. The method of analyzing threshold by changing duty cycle of pump light is proposed, and the power at threshold point is 3.75 W for the pump duty cycle of 1/25. The relationship between output signal and wavelength spacing between signal and pump is discussed, and the optimal wavelength spacing is 5.8 nm at the threshold point. Experimental results show that when the duty cycle D=1/25, the pulse can be suppressed by 114.47 ps. The noise suppression result is given through eye diagram analysis of a receiver thresholder system built for the experiments.