Abstract

Narrow-linewidth single-frequency sources in the 1.55μm wavelength region are important devices for coherent optical communication. A number of erbium-doped-fibre laser devices have been demonstrated at this wavelength in Fabry-Perot¹ and ring² configurations showing high efficiency and broad tunability³. However, to date only one report exists to our knowledge of single-frequency operation of an erbium-doped-fibre laser and this consisted of a bi-directional ring laser configuration⁴. We show in this work that elimination of spatial hole burning in the gain medium by uni-directional operation of an erbium-fibre ring laser enables single longitudinal-mode operation. A cavity length of several metres gave rise to a very narrow measured linewidth of ≤60kHz.

© 1990 Optical Society of America