According to embodiments of the present invention, an external cavity
laser includes one or more tuning elements. At least one modulated
voltage signal or dither is used to lock the transmission peak of the two
tuning elements to each other. The wavelength of the laser also may lock
onto the lock transmission peaks. In embodiments in which two dither
signals are used, the dither signals may be orthogonal to or independent
of each other. The two dither signals may produce two control signals to
align the transmission peak of one filter to the transmission peak of
another filter and the lasing mode of the laser to the aligned filters.