本文报道了一种2 μm 波段可调谐主动锁模光纤激光器，增益介质为4 m 铥钬共掺光纤。主动锁模脉冲采用强度调制方式实现，调制信号为高频正弦信号。可调谐窄带宽光滤波器用来窄化激光线宽，抑制噪声，同时可实现波长调谐。实现了稳定的2.2 GHz 重复频率主动锁模脉冲输出，对应649 阶谐波锁模脉冲序列，脉冲宽度约为200 ps，频谱信噪比可达68 dB，激光线宽为0.05 nm，光谱调谐范围为1907 nm～1927 nm。

We demonstrate a tunable actively mode-locked fiber laser at 2 μm band. A segment of 4 m Tm-Ho-co-doped fiber is used as gain medium. Active mode locking pulse is realized by using intensity modulation and the signal source is high frequency sinusoidal signal. A tunable narrow bandwidth optical filter is used to narrow laser linewidth, suppress noise and achieve wavelength tuning. Stable actively mode-locked pulses with up to 2.2 GHz repetition rate is obtained, corresponding to 649 order harmonic mode-locked pulse train. The pulse width is about 200 ps. The signal-to-noise ratio of RF spectrum is 68 dB. The optical tuning range is 1907 nm~1927 nm.