Method of and device for driving optical modulator, and optical communications system

An optical communications system comprising:

• a first terminal station having an optical transmitter;
• a second terminal station having an optical receiver;
• and
• an optical fiber transmission path for coupling said first and second terminal stations to each other, said optical transmitter comprising
• a light source for outputting carrier light therefrom,
• an electro-absorption optical modulator for receiving the carrier light therein and absorbing the carrier light according to an applied voltage to thereby output signal light subjected to intensity modulation,
• a bias circuit for generating a bias voltage determined so that said optical modulator has a given chirping parameter,
• a driving circuit for generating a modulating signal corresponding to an input signal in response to the input signal, superimposing the modulating signal on the bias voltage and supplying the result of superimposition to said optical modulator as the applied voltage, and
• a control means for controlling at least one parameter selected from a parameter group including the amplitude and duty of the modulating signal and the power of the carrier light, based on the bias voltage.

A method of driving an electro-absorption optical modulator for receiving therein carrier light emitted from a light source and absorbing the carrier light according to an applied voltage to thereby output signal light subjected to intensity modulation, comprising the steps of:

• (a) generating a bias voltage determined so that said optical modulator has a given chirping parameter;
• (b) generating a modulating signal corresponding to an input signal, superimposing the modulating signal on the bias voltage and supplying the result of superimposition to said optical modulator as the applied voltage;
• and
• (c) controlling at least one parameter selected from a parameter group including the amplitude and duty of the modulating signal and the power of the carrier light, based on the bias voltage.

A device for driving an electro-absorption optical modulator for receiving therein carrier light emitted from a light source and absorbing the carrier light according to an applied voltage to thereby output signal light subjected to intensity modulation, comprising:

• a bias circuit generating a bias voltage determined so that said optical modulator has a given chirping parameter;
• a driving circuit generating a modulating signal corresponding to an input signal in response to the input signal, superimposing the modulating signal on the bias voltage and supplying the result of superimposition to said optical modulator as the applied voltage;
• and
• a controller controlling at least one parameter selected from a parameter group including the amplitude and duty of the modulating signal and the power of the carrier light, based on the bias voltage.

An optical communications system comprising:

• a first terminal station having an optical transmitter;
• a second terminal station having an optical receiver;
• and
• an optical fiber transmission path coupling said first and second terminal stations to each other, wherein said optical transmitter comprises
• a light source outputting carrier light therefrom,
• an electro-absorption optical modulator receiving the carrier light therein and absorbing the carrier light according to an applied voltage to thereby output signal light subjected to intensity modulation,
• a bias circuit generating a bias voltage determined so that said optical modulator has a given chirping parameter,
• a driving circuit generating a modulating signal corresponding to an input signal in response to the input signal, superimposing the modulating signal on the bias voltage and supplying the result of superimposition to said optical modulator as the applied voltage, and
• a controller controlling at least one parameter selected from a parameter group including the amplitude and duty of the modulating signal and the power of the carrier light, based on the bias voltage.