研究了限制ＦＯＲＤＬ最佳陷波特性实现的主要系统因素——相位感生的强度噪声（ＰＩＮ），给出了其在单模条件下的频率特性。由此出发，分析了影响ＰＩＮ的几个因素，提出了抑制ＰＩＮ的三个途径：（１）采用极化控制器适当调节两个正交极化模式的强度（ｒ）；（２）增加环路损耗ｅＬ；（３）使ＬＤ工作于略高于Ｉｔｈ处，降低其相干时间τｃ。实验中采用这些方法将ＰＩＮ降至－５０ｄＢ／ＭＨｚ。通过微调环路损耗以满足最佳陷波条件使ＦＯＲＤＬ的陷波深度达到了６５ｄＢ。 The main system factor that restricts the realization of the FORDL optimal notch characteristic, the phase-induced intensity noise (PIN), is given and its frequency characteristics under single-mode conditions are given. Based on this, several factors that affect the PIN are analyzed and three ways to suppress the PIN are proposed: (1) to adjust the intensity (r) of the two orthogonal polarization modes by the polarization controller; (2) to add the ring Road loss eL; (3) LD work slightly above Ith Department, reduce its coherence time τc. In these experiments, these methods were used to reduce the PIN to -50 dB / MHz. FORDL notch depth of 65dB is achieved by fine tuning the loop loss to meet the best notch conditions.