A tunable Q-switched erbium fiber laser based on one all fiber structure as both saturable absorber and filter

We demonstrated a tunable Q-switched Er-doped fiber laser (EDFL) by employing one single mode fiber–step-index multimode fiber–single mode fiber (SMF–SIMF–SMF) structure as both saturable absorber (SA) and filter. Such SMF–SIMF–SMF structure is based on multimode interference. A tunable Q-switched EDFL with a tuning range from 1553 to 1569 nm was achieved by bending SIMF. When the Q-switched fiber laser operated at 1560 nm, a repetition rate of 84 kHz was obtained, together with pulse width and pulse energy of 1. 47 μ s and 104.7 nJ under the maximum pump power of 800 mW. Our results show that the SMF–SIMF–SMF structure is promising difunctional device for wavelength and pulse modulation.