用延迟自外差法分析了调频激光器的光谱线型。从理论上给出了调频激光器的线型表达式，理论结果表明，用延迟自外差法测得的调频激光器的线型是与调制函数及测试系统有关的传递函数和激光器自然线型的卷积。根据所获得的调频激光器线型表达式，分析了线型和激光器调制频率以及延迟光纤长度的关系。实验对理论分析进行了验证。

The line shape of power spectrum of frequency-modulated laser with delayed self-heterodyne method is presented. Theoretical analysis is carried out and a mathematical expression is used to describe the line shape. According to the theoretical results, the line shape of frequency-modulated laser measured by delayed self-heterodyne method is the convolution of the natural line shape and the transfer function related with the modulation signal and the testing system. The dependence of line shape on the modulation frequency and the length of optical delay is analyzed based on the obtained expression. Experiments are carried out and the testing results verify the theoretical analysis results.