研究了掺镱全光纤激光振荡器中横向模式不稳定效应与受激拉曼散射之间的关系。在纤芯直径为20 μm的单端抽运1.5 kW级全光纤激光振荡器中，当受激拉曼散射达到一定阈值时，横向模式不稳定效应突然出现，激光器输出功率突然减小，减小的输出功率由包层光滤除器倾泻到谐振腔外。实验发现：受激拉曼散射光谱增强、输出功率减小与包层光滤除器温度上升存在一定的关联; 通过缩短光纤长度抑制受激拉曼散射，可以将单端抽运激光振荡器的横向模式不稳定阈值增大到2 kW以上。对纤芯直径为25 μm的双端抽运激光振荡器进行研究，同样通过抑制受激拉曼散射增大了横向模式不稳定阈值，获得了大于5 kW的激光功率输出。实验结果初步验证了在非线性较强的情况下，受激拉曼散射是导致横向模式不稳定的原因，通过抑制受激拉曼散射可以增大横向模式不稳定阈值。

The relationship between transverse mode instability effect and stimulated Raman scattering (SRS) in Ytterbium doped all-fiber laser oscillator is studied. In the single-end pumped 1.5 kW class all-fiber laser oscillator with core diameter of 20 μm, when the stimulated Raman scattering reaches to a certain value, the transverse mode instability effect appears, in this case, the power in the laser oscillator decreases. The decreased power is stripped out of the laser oscillator by the cladding light stripper. It is found in the experiment that the enhancement of the stimulated Raman scattering spectrum, the decrease of the fiber laser power, and the increase of the temperature of the cladding light stripper have an inherence relationship. By shortening the fiber in the laser to mitigate the stimulated Raman scattering, we can increase the transverse mode instability threshold in the single-end pumped laser oscillator up to 2 kW. Similar results by increasing transverse mode instability threshold employing suppression the stimulated Raman scattering are also validated in the double-side pumped all-fiber laser oscillator with fiber core diameter of 25 μm, and laser output greater than 5 kW is demonstrated. The experimental results validates that when the nonlinear effect is somewhat strong, the stimulated Raman scattering is the reason for the transverse mode instability. By mitigating the stimulated Raman scattering effect, we can also increase the transverse mode instability threshold.