SIMULTANEOUS ABSOLUTE FREQUENCY CONTROL OF LASER TRANSMITTERS IN BOTH1.3 AND 1.55 MU-M BANDS FOR MULTIWAVELENGTH COMMUNICATION-SYSTEMS

Absolute frequency control will be an essential part of future Dense W DM systems, In this paper, we demonstrate two promising techniques tha t allow the absolute frequency control of an ensemble of laser transmi tters operating in both the 1.3 and 1.55 mu m Bands. First, a Michelso n interferometer is absolutely calibrated by means of a frequency-stab ilized master DFB laser, This interferometer provides an ensemble of e venly-spaced absolute frequency references that covers both the 1.3 an d 1.55 mu m regions. Lasers are frequency-locked to transmission nulls of this interferometer with a precision of a few hundred MHz. The sec ond technique allows full flexibility in channel frequency assignment and relies on frequency offset control of an ensemble of laser sources relative to a master reference laser. The frequency comparator is bas ed on a surface-emitting nonlinear semiconductor multilayer waveguide, This technique provides simultaneous frequency measurement and contro l of lasers in both bands with a precision of a few GHz.