A WDM device having a controller that individually controls the operating parameters of tunable lasers and the temperatures of an optical multiplexer and etalon. The device employs a spectral analyzer to measure the spectral composition of the optical output signal produced by the device. Based on the analyses of the measured spectral composition, the controller sets the temperatures of the tunable lasers, optical multiplexer, and optical etalon to values that cause: (i) middle frequencies of transmission bands of the optical multiplexer to be spectrally aligned with the corresponding frequencies of the specified frequency grid, (ii) each laser line to be properly positioned within the corresponding transmission band, and (iii) transmission resonances of the optical etalon to be properly positioned with respect to the laser lines.