Controller of optical transmitter

A controller, comprising:

• an amplification ratio control unit configured to generate an amplification ratio signal based on an ambient temperature of a laser diode;
• an amplification unit configured to
• amplify, based on the amplification ratio signal, a detection current from a photodiode configured to detect light output from the laser diode, and
• output the detection current as a voltage signal, wherein the amplification ratio signal controls an amplification ratio of the amplification unit;
• a digital conversion unit configured to convert the voltage signal into a digital signal;
• and
• a driving current control unit configured to control a driving current of a driver configured to drive the laser diode based on the digital signal,
• wherein the amplification unit comprises an amplifier and a resistor connected in parallel to the amplifier,
• the photodiode is a monitoring photodiode, the amplifier is a transimpedance amplifier and the resistor is a variable resistor, and
• the variable resistor is varied based on the ambient temperature of the laser diode.

A controller comprising:

• a reference current providing unit configured to generate a reference current;
• an amplification ratio control unit configured to generate an amplification ratio signal based on an ambient temperature of a laser diode and a level of the reference current;
• an amplification unit configured to
• amplify a detection current from a photodiode configured to detect light output from the laser diode and the reference current, and
• output the detection current and the reference current as a voltage signal, wherein the amplification ratio control unit controls an amplification ratio of the amplification unit;
• a digital conversion unit configured to convert the voltage signal into a digital signal;
• and
• a driving current control unit configured to control a driving current of a driver configured to drive the laser diode according to the digital signal,
• wherein the digital conversion unit comprises:
• an analog-to-digital converter configured to convert the voltage signal into a digital signal;
• and
• an offset removal unit configured to differentiate a digital signal corresponding to a default current of the photodiode in the digital signal from the analog-to-digital converter.

A controller, comprising:

• a reference current providing unit configured to generate a reference current;
• an amplification ratio control unit configured to generate an amplification ratio signal based on an ambient temperature of a laser diode and a level of the reference current;
• an amplification unit configured to
• amplify a detection current from a photodiode configured to detect light output from the laser diode and the reference current, and
• output the detection current and the reference current as a voltage signal, wherein the amplification ratio control unit controls an amplification ratio of the amplification unit;
• a digital conversion unit configured to convert the voltage signal into a digital signal;
• and
• a driving current control unit configured to control a driving current of a driver configured to drive the laser diode according to the digital signal,
• wherein the amplification unit comprises an amplifier and a resistor connected in parallel to the amplifier,
• the photodiode is a monitoring photodiode, the amplifier is a transimpedance amplifier and the resistor is a variable resistor, and
• the variable resistor is varied based on the reference value and the ambient temperature of the laser diode.