Optical transceiver device, optical modulator control method, and non-transitory computer readable medium storing optical modulator control program

An optical modulator control method comprising:

• controlling a bias voltage of an optical modulator that is configured to modulate a continuous light from a light source by a control signal and periodically updating the control signal at predetermined cycles;
• setting the control signal at two stages including a preliminary search executed only at a time of an initial startup and a feedback proportional control periodically executed for each cycle of the predetermined cycles;
• setting the control signal used at a time of starting the feedback proportional control subsequently executed as a reference value in the preliminary search;
• repeating, in the feedback proportional control, the following processing of starting control of the optical modulator by setting the control signal to the reference value set in the preliminary search or a reference value stored in the feedback proportional control in a previous cycle, calculating a new reference value based on an error signal obtained from the optical modulator as a result of controlling the optical modulator, and controlling the optical modulator by setting the control signal to the calculated new reference value, thereby acquiring the control signal in which the error signal is minimized as an optimal control signal and setting the optimal control signal as the control signal for controlling the optical modulator, and storing the set optimal control signal as a reference value to be used at a time of starting the feedback proportional control in a next cycle, and
• selecting, in the preliminary search, a predetermined number of control signals in a predetermined range in which it is assumed that the error signal may be minimized, controlling the optical modulator using each of the predetermined number of control signals, and setting one of the predetermined number of control signals that minimizes the error signal as the reference value, wherein
• in the feedback proportional control, a search range for a minimum value of the error signal is set and centered about the reference value set in the preliminary search.

A non-transitory computer readable medium storing an optical modulator control program, that, when executed by a computer, cause the computer to:

• control a bias voltage of an optical modulator that is configured to modulate a continuous light from a light source by a control signal and periodically update the control signal at predetermined cycles;
• set the control signal at two stages including a preliminary search executed only at a time of an initial startup and a feedback proportional control periodically executed for each cycle of the predetermined cycles;
• set the control signal used at a time of the feedback proportional control subsequently executed as a reference value in the preliminary search;
• repeat, in the feedback proportional control, the following processing of starting control of the optical modulator by setting the control signal to the reference value set in the preliminary search or a reference value stored in the feedback proportional control in a previous cycle, calculating a new reference value based on an error signal obtained from the optical modulator as a result of controlling the optical modulator, and controlling the optical modulator by setting the control signal to the calculated new reference value, thereby acquiring the control signal in which the error signal is minimized as an optimal control signal and setting the optimal control signal as the control signal for controlling the optical modulator, and storing the set optimal control signal as a reference value to be used at a time of starting the feedback proportional control in a next cycle, and select, in the preliminary search, a predetermined number of control signals in a predetermined range in which it is assumed that the error signal may be minimized, control the optical modulator using each of the predetermined number of control signals, and set one of the predetermined number of control signals that minimizes the error signal as the reference value, wherein in the feedback proportional control, a search range for a minimum value of the error signal is set and centered about the reference value set in the preliminary search.