Tunable Multi-Wavelength Bright-Dark and Dark-Bright Pulse Pairs Fiber Lasers

We have experimentally demonstrated tunable multi-wavelength bright-dark and dark-bright pulse pairs in an all normal dispersion Yb-doped fiber laser (YDFL) with a long cavity configuration. By carefully adjusting the pump power and the polarization state, bright-dark pulse pairs could be converted into dark-bright pulse pairs at the same wavelength. The comb filter provided by the tapered fiber facilitated the formation of the multi-wavelength pulses. And the wavelength-tunable for both bright-dark pulse pairs and dark-bright pulse pairs could be achieved by using a tapered fiber and rotatable polarization controller in the cavity to control the cavity losses. The tunable ranges were 14 nm and 4 nm with wavelength spacings of similar to 3.5 nm and similar to 3.7 nm for dual-wavelength pulse pairs and triple-wavelength pulse pairs, respectively.