Using optimal cavity loss and saturable-absorber passive filter for stable and tunable dual-wavelength erbium fiber laser in single-longitudinal-mode operation

In this investigation, we propose and demonstrate experimentally tunable and stable dual‐wavelength erbium doped fiber (EDF) double‐ring laser scheme using different coupling losses inside cavity loop for wavelength and mode spacing tuning. Besides, a shorter unpumped EDF is also used to filter the side‐modes for lasing wavelength in singlelongitudinal‐mode (SLM) operation. However, the output mode spacing of dual‐wavelength could be limited owing to the homogeneous broadening nature of EDF. As a result, the output performance of the proposed fiber laser have also been analyzed and discussed, such as wavelength tuning range, output power, side‐mode suppression ratio (SMSR), stabilities of lasing wavelength and power, relative intensity noise (RIN), etc. (© 2011 by Astro Ltd., Published exclusively by WILEY‐VCH Verlag GmbH & Co. KGaA) (© 2011 by Astro Ltd., Published exclusively by WILEY‐VCH Verlag GmbH & Co. KGaA)