Abstract

Stable and reliable frequency references are required for the practical implementation of multiwavelength fiber-optic networks.¹ Locking the emission wavelength of a laser source to molecular absorption lines may result in good short- and longterm frequency stability, good reproducibility, and, with the use of particular techniques,^2,3 the absence of undesired frequency modulation. Near 1.5 pm a few atomic (Ne, Rb) or molecular (NH₃, C₂H₂, HCN) species have been identified and studied in view of frequency stabilization; in the first two cases excited-state absorption is used, whereas in the case of molecules, overtones or combinations of roto-vibrational states are used. A more detailed search for new, alternative absorbers is necessary for finding lines in addition to those already reported, particularly those falling under the erbium-doped-fiber amplifier (EDFA) gain curve.

© 1993 Optical Society of America