The invention provides a method to compensate for degradation in a tunable
laser and ensure its performance by tracking the degradation and
adjusting the control information accordingly. This is accomplished by
performing some measurements of the output of the tunable laser at an
initial setup or calibration procedure. Then, by effecting a periodic
repetition of these measurements and using a comparison between these two
measurements the present invention provides for a compensation factor for
the operating conditions, primarily in the form of a look up table of
operating points of the laser. These measurements show how much the
operating points of the laser have drifted over the period since the last
set of measurements, which provide control informatIon to compensate for
degradation in the laser.