Tunable single-wavelength erbium-doped fiber ring laser using a large-core fiber

In this paper, a tunable single-wavelength erbium-doped fiber ring laser is proposed. A novel fiber filter based on a large-core fiber is developed for suppressing the mode competition in erbium-doped fiber lasers (EDFLs). Under the pump power of 250 mW, single-wavelength lasing output is implemented with a side mode suppression ratio (SMSR) higher than 55 dB. By adjusting the curvature applied on the large-core fiber, stably tunable single-wavelength lasing output within the wavelength range from 1552.4 nm to 1563.2 nm is obtained with a 3 dB linewidth of 0.2 nm. Furthermore, the wavelength shift and peak power fluctuation are controlled within 0.02 nm and 0.5 dB by monitoring the lasing output with an interval of 6 min in one hour, respectively. A contrast experiment of a laser without tapering LCF is carried out to examine the importance of the taper in LCF-based filter. Experimental results demonstrate that the side modes of the lasing output can be effectively suppressed and thus SMSR can be improved from 41 dB to 58 dB by using a taper.