▎ 摘　　要

A tunable Q-switched erbium-doped fiber laser using a singlemode-multimode-singlemode fiber structure as a wavelength tuning filter and a graphene oxide saturable absorber is proposed and demonstrated. The system allows the Q-switched laser to be tuned between the wavelengths of 1550.78 nm and 1560.62 nm, giving a tuning range of 9.84 nm. At a Q-switched laser wavelength of 1552.75 nm, a repetition rate of 39.1 kHz and pulse width of 3.6 mu s, as well as an average output power of 1.32 mW and pulse energy of 33.8 nJ at a maximum pump power of 79 mW are obtained. Radio frequency analysis shows an average signal-to-noise ratio of 38.8 dB across the measured operating wavelengths, confirming that the system is stable and reliable, with small pulse width and intensity fluctuations.