主要研究了外加光反馈对光纤布拉格光栅外腔半导体窄线宽激光器特性的影响。在研究温度对光纤光栅外腔半导体激光器激射波长影响的基础上，设计了强度可调的外加光反馈系统，并利用延时自外差法测试外腔半导体激光器的线宽，从实验上分析了不同强度的外加光反馈对外腔半导体激光器线宽和噪声的影响。实验结果表明，在外加光反馈强度逐渐增强的过程中，激光器线宽逐渐变窄。当反馈比为-22 dB时，激光器线宽被压窄至原始线宽的15%。与此同时，在相同的反馈变化下，激光器的相对强度噪声开始无明显变化，直到反馈比达到-27 dB。再继续增大反馈强度，相对强度噪声显著增大，激光器内部发生相干崩塌。

Influences of external optical feedback effects on characteristic of the fiber Bragg grating external cavity semiconductor laser are investigated. When the effect of temperature on the wavelength of external cavity semiconductor laser is taken into account, an external optical feedback setup is built, and the optical feedback intensity can be adjusted. The linewidth of the external cavity semiconductor laser is measured by delayed self-homodyne technique, and the changes of linewidth and noise of the laser with different external optical feedback are analyzed. Experimental results show that the linewidth of the laser decreases when the optical feedback intensity increases. The linewidth is narrowed down to 15% of the original one when the feedback ratio reaches -22 dB. Meanwhile, within the same variation of the optical feedback, the relative intensity noise of the laser has no obvious change until the feedback ratio increases to -27 dB. As the feedback further increases, the relative intensity noise of laser increases significantly and the coherent collapse happens inside of lasers.