Driver circuit for tunable ld

A driver circuit to drive a wavelength tunable laser diode comprising an SG-DFB region to generate light, a CSG-DBR region to determine a wavelength of said light, and an SOA region to amplify said light generated in said SG-DFB region and said wavelength thereof being determined said by said CSG-DFB region, comprising:

• a first current source configured to bias said SG-DFB region to generate said light;
• a second current source configured to bias said CSG-DBR region to provide current to a heater implemented within said CSG-DBR region;
• a third current source configured to bias said SOA region;
• a DC/DC converter to supply an output to said first to third current sources;
• and
• a voltage controller to control said output of said DC/DC converter by monitoring a bias level of said SG-DFB region by said first current source, a bias level of said CSG-DBR region by said second current source, and a bias level of said SOA region by said third current source,
• wherein said output of said DC/DC converter is set to be equal to a value greater than a bias level largest among said bias levels by a preset margin to operate said first to third current sources normally.

A driver circuit to drive a wavelength tunable LD including an SG-DFB region to generate light, a CSG-DBR region to determine a wavelength of said light, and an SOA region to amplify said light generated in said SG-DFB region and said wavelength thereof determined by said CSG-DBR region, comprising:

• a first current source configured to bias said SG-DFB region to provide a first current;
• a second current source configured to bias said CSG-DBR region to provide a second current;
• a third current source configured to bias said SOA region to provide a third current;
• a first DC/DC converter to supply a first output to said first current source and said second current source;
• a second DC/DC converter to supply a second output to said third current source;
• and
• a voltage controller configured to monitor individually a first bias level of said SG-DFB region by said first current source, a second bias level of said CSG-DBR region by said second current source, and a third bias level of said SOA region by said third current source,
• wherein said voltage controller sets said first output of said first DC/DC converter to be equal to a value larger than a largest bias level among said first bias level and said second bias level by a preset margin necessary to operate said first and second current sources normally, and
• wherein said voltage controller sets said second output of said second DC/DC converter to be equal to a value larger than said third bias level by said present margin.

A method to control a wavelength tunable LD that includes a SG-DFB region to generate light by being provided with a current from a first current source, a CSG-DBR region to determine a wavelength of said light by being provided with a second current from a second current source, and an SOA region to amplify said light by being provided with a third current from a third current source, said method comprising steps of:

• setting an output of a DC/DC converter commonly connected to said first to third current sources in a value enough higher than a value necessary to operate said current sources normally;
• selecting said wavelength by adjusting said first current provided to said SG-DFB region and said second current provided to said CSG-DBR region;
• setting a magnitude of said light by adjusting said third current provided to said SOA region;
• determining a maximum bias voltage among bias voltages each provided to said SG-DFB region, said CSG-DBR region and said SOA region by said first to third current sources, respectively, by monitoring said bias voltages;
• and
• decreasing said output of said DC/DC converter in another voltage larger than said maximum voltage by a preset margin necessary to operate said current sources normally.