40-nm-wide tunable fiber ring laser with single-mode operation using a highly stretchable FBG

In this letter, we demonstrate a 750-Hz linewidth single-mode erbium-doped fiber (EDF) ring laser with wide tunability using a widely tunable fiber Br agg grating (FBG). The stable single-mode operation is realized by using th e FBG as a narrow wavelength-selective element and 4 in of unpumped EDF as a saturable absorber in the cavity. The 40-nm continuous tuning range of 15 22-1562 nm is achieved using a highly stretchable FBG that exhibits a filte r tuning range of over 52 nm. The grating is prepared with chemically strip ped Deuterium-loaded fiber to eliminate degrading factors for the grating s trength, thereby achieving the wide tunability. The tuning range represents a 3.5-fold increase in wavelength tuning over prior art using FBGs.