报道了一种长腔掺镱锁模光纤激光器。除用以实现自启动锁模的非线性偏振旋转（NPR）元件外，激光器为全单模光纤结构，且腔内无色散补偿元件，工作在全正色散域，仅仅通过引入窄带滤波器参与脉冲整形过程输出耗散孤子。实验中通过延长单模光纤长度实现了两个长腔条件，分别得到了6.66 MHz重复频率，12 nJ单脉冲能量和5.05 MHz重复频率，20 nJ单脉冲能量的稳定锁模脉冲，噪声抑制比均为75 dB。与以往的全正色散锁模光纤激光器相比，重复频率低，单脉冲能量高，稳定性好，适用于构建简化的光纤啁啾脉冲放大（CPA）系统。

A long-cavity mode-locked Yb-doped fiber laser is reported. The laser consists of only single mode fiber (SMF) components except the nonlinear polarization rotation (NPR) parts which are utilized to achieve self-starting mode-locking, and operates at the all-normal-dispersion (ANDi) region since there are no dispersion compensation elements inside the cavity. Dissipative solitons were obtained via the introduction of only a narrow-bandwidth spectral filter into the pulse shaping process. Two long-cavity conditions were implemented by lengthening the SMF, where pulses with 6.66 MHz repetition rate and 12 nJ single pulse energy and those with 5.05 MHz repetition rate and 20 nJ single pulse energy were obtained respectively, both showing a noise suppression ratio of 75 dB on the radio frequency (RF) spectra. Compared to the former ANDi mode-locked fiber lasers, this laser operates at a lower repetition rate with higher single pulse energies and better stability, which should be useful in the construction of a simplified fiber chirped pulse amplification (CPA) system.