提出了一种主动锁模光电振荡器（OEO）方案，可以实现高阶谐波锁模，从而产生具有高重复频率的微波脉冲信号。在所提方案中，通过在OEO腔内的电光强度调制器直流偏置端口引入一个正弦驱动信号，当该正弦信号的频率 ${f_{bias}}$为OEO环腔自由光谱范围的整数倍 $N$时，实现基频（ $N = 1$）或谐波（ $N \geqslant 2$）锁模，输出重复频率为 ${f_{bias}}$的微波脉冲信号。实验中分别实现了10阶、50阶和100阶谐波锁模，输出微波脉冲信号的重复频率分别为360 kHz、1.8 MHz和3.6 MHz。该方案为脉冲多普勒雷达等系统应用提供了一种全新的、具备低相噪潜力的微波脉冲信号产生的技术途径。

The pulse dynamics of harmonic mode-locking in a dissipative soliton resonance (DSR) region in an erbium-doped fiber ring laser is investigated at different values of anomalous dispersion. The fiber laser is mode-locked by a nonlinear polarization rotation technique. By inserting 0–200 m anomalous dispersion single-mode fiber in the laser cavity, the cavity length is changed from 17.3 to 217.3 m, and the corresponding dispersion of the cavity ranges from ?0.27 to ?4.67 ps2. The observed results show that the tuning range of repetition rate under a harmonic DSR condition is highly influenced by the cavity dispersion. Furthermore, it is found that, by automatically adjusting their harmonic orders, the lasers can work at certain values of repetition rate, which are independent of the cavity length and dispersion. The pulses at the same repetition rate in different laser configurations have similar properties, demonstrating that each achievable repetition rate represents an operation regime of harmonic DSR lasers.

We report an erbium-doped fiber laser passively Q-switched by a few-layer molybdenum disulfide (MoS2) saturable absorber (SA). The few-layer MoS2 is grown by the chemical vapor deposition method and transferred onto the end-face of a fiber connector to form a fiber-compatible MoS2 SA. The laser cavity is constructed by using a three-port optical circulator and a fiber Bragg grating (FBG) as the two end-mirrors. Stable Q-switched pulses are obtained with a pulse duration of 1.92 μs at 1560.5 nm. By increasing the pump power from 42 to 204 mW, the pulse repetition rate can be widely changed from 28.6 to 114.8 kHz. Passive Q-switching operations with discrete lasing wavelengths ranging from 1529.8 to 1570.1 nm are also investigated by using FBGs with different central wavelengths. This work demonstrates that few-layer MoS2 can serve as a promising SA for wideband-tunable Q-switching laser operation.

A novel method for accurately measuring chromatic dispersion of optical fibers is proposed based on the use of chirped intensity-modulated signals. Unlike the conventional method, the proposed method utilizes the configurable transfer function of optical fibers caused by the residual chirp of intensity modulation, which not only eliminates the chirp error but also improves the measurement range through adjusting the chirp parameter of the intensity modulator. Our method is applicable for measuring both the magnitude and sign of chromatic dispersion of optical fibers or other dispersive devices at different operating wavelengths by using a vector network analyzer.