A method of characterizing a tunable semiconductor laser diode by varying
the laser tuning currents of a section, and measuring the output power
transmitted by the laser through a wavelength discriminating device
(WDD), in such a way that determines the currents needed to optimize the
laser output within the passband of the WDD. A preferably employed method
is to align the laser to the center of the passband, in order to maximize
transmission. Since the laser alignment is performed relative to the
spectral response curve of the WDD, there is no need to know the actual
wavelength, either of the laser, or of the WDD. The WDD may be a
multiplexer, a demultiplexer, an optical filter, or even a complete
communications channel. The latter case thus constitutes a method of
optimizing the performance of an optical communications channel by
optimizing the wavelength of its laser source to the channel.