Study on the Effect of Reflected Lights on Mode Partition Characteristics of Dynamic Single-Mode Laser Diodes

本文通过实验研究了分布式反馈激光二极管（DFB LD）的模式分配特性，并通过计算机仿真研究了其噪声产生机理。得到了以下结果：用时间分辨光谱法观察了DFB LD的瞬态光谱，表明即使直接调制为Gb/s.2， DFB LD也存在单纵模振荡。非相干反射引起的模式分配噪声随着直流偏置电流的增大而增大。这种噪声增加的原因是由于反射光和led内部的光之间的干涉导致主模式阈值的调制。建立了控制相干反射光振幅和相位的实验装置。在直接调制DFB LD的光谱中，发现相干反射增强了短波分量。测量和计算机模拟正在进行中。

In this research, the mode partition characteristics of distributed feedback laser diodes (DFB LD's)are experimentally evaluated, and the noise generation mechanisms are investigated by a computer simulation. The following results are obtained.1.By observing the transient spectra of DFB LD's with the time resolving spectroscopic method, it is made clear that DFB LD's oscillate in single longitudinal mode even if they are directly modulated at Gb/s.2.The mode partition noise induced by incoherent reflections is found to increase with the DC bias current. The origin of this noise increase is attributed to the modulation of the threshold of the main mode due to the interference between the reflected light and the light inside of the LD.3.An experimental setup to control the amplitude and the phase of the coherently reflected light is established. In the spectra of directly modulated DFB LD's, it is found that the short wavelength components are enhanced by the coherent reflections. The measurements and the computer simulations are in progress.