The generation and observation of pulses with switchable single/dual wavelengths and tunable bandwidth from a SWNT mode-locked Er-doped fiber laser

•Mode-locked pulses with switchable wavelengths and tunable bandwidth from a single all-fiber cavity.•Widely-bandwidth-tunable pulses centered in 1530- or/and 1550-nm gain regions of EDF.•Pulse outputs based on multiple soliton formation mechanisms combining nanomaterial saturable absorber, intracavity loss tuning and nonlinear polarization rotation.