中文摘要：

针对已有线宽检测方法在窄线宽激光器测量中存在的缺陷，提出一种利用非平衡光纤干涉仪相位噪声测量并计算线宽的方法。理论分析了短程差非平衡干涉仪相位噪声与窄线宽激光器的光频噪声的关系，得到了激光器的光波功率频谱和线宽。利用臂差为10m的光纤干涉仪对窄线宽分布反馈激光器进行测量，结果表明激光器光波功率谱有近似的洛伦兹线型且线宽为5．4kHz，与5kHz的理论值相近。窄线宽光纤环形腔激光器的线宽测量结果为0．75kHz，比用零拍法测量到的同类型激光器低于1．5kHz的结果更精确。

英文摘要：

In order to solve problems in linewidth measurement for narrow linewidth laser, a method is put forward based on the phase noise of unbalanced fiber-optic interferometer. The relationship between the phase noise of an unbalanced fiber-optic interferometer with a short optical path difference （OPD） and the laser frequency iitter is analyzed, and the optical power spectrum and linewidth are obtained. The linewidth of a distributed feedback laser is tested using an interferometer with 10 m OPD. The result shows that the power spectrum is an approximate Lorentzian lineshape with 5.4 kHz linewidth, which is close to the theoretical value of the laser. The linewidth of a fiber ring laser （FRL） is tested and the result is 0.75 kHz, which is more accurate than the result of less than 1.5 kHz of the similar FRL obtained using homodyne method.