Output power characteristics of tunable erbium-doped fiber ring lasers

The output power characteristics of a widely tunable erbium-doped fiber ring laser (EDFRL) have been analyzed. The effects of emission wavelength, total intracavity loss, erbium ion clustering, output coupling ratio, and active fiber length are investigated. A comprehensive theoretical model based on a two-level laser model with consideration of pair-induced quenching is proposed. To achieve good performance in an EDFRL, especially for a widely tunable bandwidth of over 100 nm and high slope efficiency, numerical results, which are in good quantitative agreement with the experimental results, indicate that minimization of the intracavity loss as well as optimization of the active fiber length and the output coupling ratio are very important. It is found that the existence of erbium ion clusters in the active fiber can help an EDFRL to emit at a longer wavelength, and hence may be favorable for achieving L-band laser although the output power is reduced and the power flatness is degraded significantly. These findings are useful for the design and optimization of erbium-doped fiber lasers, especially for tunable fiber lasers operating in the longer band or L-band.