Simultaneous beat-frequency locking of conventional and ultra-dense WDM channels using a modulated tunable-laser source

A beat-frequency-locking method to align conventional and ultra-dense wavelength-division-multiplexing (WDM) channels simultaneously is presented. This method finds and corrects the channel locations to within +-100 MHz, reading the beat frequencies between a sinusoidally-modulated tunable-laser source output and its adjacent optical channels. With this method, conventional WDM networks can be upgraded very easily by introducing ultra-dense WDM channels.