L-band filter-less wavelength tunable mode-locked fiber laser incorporating a long-period fiber grating

The influences on the tuning range of a wavelength-tunable L-band mode-locked fiber lasers incorporating a long-period fiber grating (LPFG) are investigated. Through controlling both resonance wavelength and bandwidth of the LPFG, the net gain of the laser can be designed appropriately, hence leading to an optimized tuning range of the L-band mode-locked lasers. A wide spectral tuning range of 23.98 nm is obtained when using the LPFG with 21.60 nm bandwidth. Benefiting from the narrow band optical attenuation characteristic of LPFG, the lowest power variation of the laser is merely 4.15 µW/nm. Moreover, theoretical gain analysis corresponds to the experimental observation well.