理论研究了直接调制与外调制模式下的微波光子链路的线性度，以直调激光器为核心器件的直接调制型短距离微波光子链路具有明显优势。着重开展实验研究，采集和分析两种调制模式下的信号，获得关键性能参数，包括链路损耗、线性动态范围(CDR)和无杂散动态范围(SFDR)。比较了不同长度光纤传输下的动态范围，发现直接调制型微波光子链路经10 km光纤传输后性能显著下降。此外，纳入直调激光器线宽、啁啾因素，实验研究了不同长度光纤下色散的影响。结果显示，直接调制型短距离微波光子链路具有高线性度的优势。

The linearity of microwave photonic link with direct modulation mode or external modulation mode is theoretically studied. The direct modulation short-range microwave photonic link, which is used direct modulation laser as the core device, has obvious advantages in linearity. Then the experiments are carried out to obtain key performance parameters through analysis of acquired signals under the two modulation modes, including the link loss, compression dynamic range (CDR) and spurious free dynamic range (SFDR). The dynamic ranges of fiber links with different lengths are compared, and the performance of the microwave photonic link with direct modulation drops significantly after the 10-km optical fiber transmission. In addition, considering the linewidth and chirp of directly modulated laser, dispersion effects for fiber links with different lengths are studied experimentally. The result shows that the microwave photonic link with direct modulation has high linearity for short-distance transmission.