Calibration of a tunable DBR laser

A method of calibrating a directly modulated tunable laser having a distributed Bragg reflector, the method comprising:

• aligning a reflection peak of the distributed Bragg reflector with a target cavity mode of a plurality of cavity modes defined by a total optical path length inside a resonant cavity defined by the distributed Bragg reflector, a phase section, and a gain section of the tunable laser;
• monitoring an optical output of the tunable laser while aligning the reflection peak of the distributed Bragg reflector with the target cavity mode to identify side modes of a resultant lasing mode formed by alignment of the reflection peak of the distributed Bragg reflector with the target cavity mode;
• aligning the resultant lasing mode with a target wavelength of an output wavelength grid;
• determining that the reflection peak is aligned with the target cavity mode when the neighboring side modes have equal amplitudes;
• and
• setting a target output power and a target extinction ratio of the tunable laser.

A method of calibrating a directly modulated tunable laser having a distributed Bragg reflector, the method comprising:

• aligning a reflection peak of the distributed Bragg reflector with a target cavity mode of a plurality of cavity modes defined by a total optical path length inside a resonant cavity defined by the distributed Bragg reflector, a phase section, and a gain section of the tunable laser, the aligning of the reflection peak comprising:
• monitoring an output power of an optical output of the tunable laser at each wavelength of an output wavelength grid while varying a modulation current delivered to the gain section of the tunable laser between a minimum modulation current and a maximum modulation current;
• determining the modulation current of the gain section of the tunable laser based on a relationship between the output power of the tunable laser and the modulation current applied to the gain section, the modulation current of the gain section of the tunable laser determined as:
• I
• mod
• =
• OMA
• S
• wherein Imod is the modulation current, OMA is an optical modulation amplitude, and S is a slope efficiency of the laser;
• and
• altering a bias current applied to the grating section of the tunable laser to align the reflection peak of the distributed Bragg reflector with the target cavity mode, the bias current of the distributed Bragg reflector of the tunable laser determined as:
• I
• bias
• =
• I
• mod
• E
• ⁢
• ⁢
• R
• -
• 1
• +
• I
• mod
• 2
• +
• I
• th
• wherein Ibias is the bias current, Imod is the modulation current, ER is a desired extinction ratio of the laser, and Ith is a threshold current;
• aligning a resultant lasing mode with a target wavelength of an output wavelength grid, the resultant lasing mode formed by alignment of the reflection peak of the distributed Bragg reflector with the target cavity mode;
• and
• setting a target output power and a target extinction ratio of the tunable laser.

A tunable laser calibration system comprising:

• a tunable laser comprising:
• a gain section;
• a distributed Bragg reflector optically connected with the gain section;
• and
• a power monitor optically connected to the gain section;
• and
• a controller in communication with the tunable laser, the controller comprising:
• non-transitory memory;
• and
• one or more data processing devices in communication with the non-transitory memory, the one or more data processing devices executing instructions configuring the one or more data processing devices to execute a calibration routine comprising:
• aligning a reflection peak of the distributed Bragg reflector with a target cavity mode of a plurality of cavity modes defined by a total optical path length inside a resonant cavity defined by the distributed Bragg reflector and the gain section of the tunable laser, the aligning of the reflection peak comprising altering a temperature of the resonant cavity of the directly modulated tunable laser by a threshold temperature increment to shift a cavity frequency grid defined by the plurality of cavity modes to align with the reflection peak of the distributed Bragg reflector;
• aligning a resultant lasing mode with a target wavelength of an output wavelength grid, the resultant lasing mode formed by alignment of the reflection peak of the distributed Bragg reflector with the target cavity mode;
• and
• setting a target output power and a target extinction ratio of the tunable laser.