Broad-spectrum, wavelength-swept, erbium-doped fiber laser at 1.55 microm

We describe an argon-ion-laser-pumped erbium-doped fiber laser at 1.55 microm that incorporates low-rate frequency modulation of an intracavity acousto-optic modulator to provide repeated, continuous tuning of the output spectrum. The spectral width of this wavelength-swept fiber laser is as large as 20 nm with 9 mW of output power, even though erbium in silica has a mostly homogeneously broadened gain. The time-averaged visibility curve for a 14-nm-wide source indicates a short (160-microm) coherence length, which is of interest for fiber-optic gyroscopes that operate with long integration times and short-coherence-length sources.