A multi-wavelength fiber laser with a narrow bandwidth based on an erbium-doped fiber ring filter and multimode fiber Bragg grating (MM-FBG) has been proposed, a high finesse fiber ring filter are introduced .The fiber ring filter consists of two optical couplers and a section of weak pumped erbium-doped fiber (EDF）. Thanks to the delay of cavity length and the gain generated by the EDF, the filter has spectral response with a high finesse. The incorporation of the fiber ring filter leads to the suppression of undesirable mode and makes the output laser narrower bandwidth. With 980 nm LD pumped, at the room temperature, the space of the two wavelengths is 0.07nm, which improved the effect of the filter.
Narrow bandwidth Q-switched Erbium-doped fiber laser based on dynamic saturable absorption filtering effect