Apparatus and method for compensating for age induced wavelength drift in tunable semiconductor lasers

This invention relates generally to tunable optical transmitters, and more particularly to prediction methods for tunable semiconductor lasers for stabilizing such lasers and for maintaining a high side mode suppression ratio (SMSR). The present invention provides a method and apparatus for compensating for the age induced wavelength drift in a tunable DBR. In practice, the tuning characteristic (i.e. output wavelength versus tuning current) of a tunable DBR may be characterized before and after factory aging, typically in the form of a burn-in or purge cycle. An aging vector may be constructed in accordance with the ratio of the change in the tuning characteristic associated with a second output wavelength and the change in the tuning characteristic associated with a first output wavelength as a function of the factory aging. In addition, the tuning characteristic associated with transmission at the first output wavelength may be monitored in the field. A controller may then update the value of the tuning characteristic associated with the second output wavelength to switch to the second output wavelength in manner that compensates for age induced wavelength drift as a function of the measured in field value of the tuning characteristic associated with transmission at a first output wavelength and said aging vector.