Multi-wavelength actively Q-switched random fiber laser based on EOM and a real-time configurable filter

Abstract

A multi-wavelength actively Q-switched random fiber laser based on real-time configurable Waveshaper and electro-optic modulator is proposed and experimentally demonstrated. The random feedback of the laser is provided by Rayleigh scattering generated by the single-mode fiber. The Waveshaper not only acts as a multi-channel filter, but also introduces wavelength-dependent losses in the laser cavity, which can suppress the mode competition caused by uniform broadening of the erbium-doped fiber and the power imbalance caused by Rayleigh scattering. Additional dispersion, group delay, phase and other parameters can be introduced through Waveshaper, and then the influence of additional quantities such as dispersion on actively Q-switched random fiber laser is studied. In the experiment, when the additional dispersion changes within -200 ~ 200 ps/nm, the pulse width of actively Q-switched can change between 1.01 ~ 1.18 μs. Compared with other experiments, this experiment further and more accurately studied the effects of dispersion, group delay and phase on actively Q-switched pulses. Because of the half-open cavity and erbium-doped fiber gain, the laser threshold is suppressed to 25 mW. The powers distribution on the wavelengths are uniform, and the amplitude difference between the ten wavelengths is < 2 dB. The side-mode suppression ratio of the laser after equalization is about 25 dB. When a triangle waveform is applied to the EOM, a dark pulse sequence output can be obtained. The proposed multi-wavelength actively Q-switched random fiber laser has the advantages of simple structure, low threshold and high stability.