Tm-Ho codoped fiber based multi-wavelength Q-switching of an Er-doped fiber laser

•The CW lasing threshold information is rephrased.•A 4 ms waveform is added.•Fluctuation of the pulse energy is quantified.

A multi-wavelength, passively Q-switched Er-doped fiber ring laser is built. With a piece of 37 cm long Tm-Ho codoped fiber which works as both a wavelength filter and a fiber saturable absorber, multi-wavelength lasing in the frequency domain and passive Q-switching in the time domain of the laser system are realized simultaneously. A broad multi-wavelength lasing from 1545 nm to 1560 nm is obtained with a spacing of about 2 nm with different pump powers. Repetition rate of the pulsed output reaches 45 kHz with a maximum pulse energy of 127 nJ. Spectral characteristics of this laser system is discussed and simulated.