Laser frequency stabilization for high bit-rate FSK multichannel coherent systems

After reviewing some previously proposed laser frequency stabilization techniques for multichannel coherent systems, the authors present a simple, alternative method, making use of a scanning Fabry-Perot resonator. This technique, which proved effective in a preliminary experiment stabilizing a single DFB (distributed feedback) laser diode within less than 500 kHz, was successfully applied to the collective stabilization of a two-channel transmitter and can be easily extended to a multichannel configuration with a high number of channels. The same principle can operate, with some modification, in the presence of FSK (frequency shift keying) direct modulation. This has been experimentally demonstrated for a DFB laser that was directly modulated up to 2 Gb/s