Patent ID: 8665917

Claim:
Method for calibrating a tunable semiconductor laser ( 121 ; 10 ) comprising at least a phase section ( 12 ) and at least a first Bragg reflector section ( 14 a , 14 b ), through which sections a phase current and a first reflector current, respectively, is applied, which laser ( 121 ; 10 ) is not actively temperature stabilized, said method comprising the steps of a) selecting at least one phase current; b) identifying for one particular phase current, selected among the phase current or currents selected in step a), a range ( 203 ) of reflector currents that in combination with the particular phase current achieves emission of light from the laser ( 121 ; 10 ) within a desired frequency band of operation for the laser ( 121 ; 10 ); c) scanning the reflector current or currents over at least the range ( 203 ) of reflector currents as identified in step b), for each of at least two different phase currents, and reading the relative output power of the laser ( 121 ; 10 ) for each point scanned; d) identifying, for each phase current as used in step c), at least one stable operating point ( 302 ) as that or those points scanned in step c) which are located between two adjacent mode boundaries, as detected as steep shifts in the relative laser output power, and possibly for which any hysteresis is minimal; e) identifying and storing into a memory at least one stable, continuous tuning line ( 305 ) as constructed by interpolating between neighboring stable operating points ( 302 ), as identified in step d), of different phase currents; f) calibrating the laser frequency by scanning along said identified tuning line ( 305 ) and observing a fed back signal ( 113 ) from a target ( 110 ) for the light emitted from the laser ( 121 ; 10 ), which signal ( 113 ) carries information about whether the light emitted by the laser ( 121 ; 10 ) is within a certain target frequency range; g) measuring the temperature of the laser ( 121 ; 10 ) when step f) was conducted; and h) storing into the memory the temperature of the laser ( 121 ; 10 ) and at least one operating point along the tuning line ( 305 ) indicative of the target frequency range.