Abstract

High-density wavelength-division multiplexing and coherent optical detection represent, among others, two of the main trends in fiber-optics communications. For both of these applications, distributed-feedback semiconductor lasers around a 1550-nm wavelength provide, at the present, the best solution. Following the recent development of Er-doped-fiber amplifiers, Er-doped-fiber lasers have been studied intensively during the last few years for many potential applications in optical communications, including tunable single-mode operation.¹ The frequency separation between longitudinal modes is, however, very small in this case (generally a few tens of megahertz), and singlemode operation without mode hopping seems to be difficult to achieve.

© 1993 Optical Society of America