Method, device, and system for waveform shaping of signal light

A method comprising:

• (a) dividing, by an interferometer, signal light into first signal light and second signal light, wherein each of said first signal light and said second signal light includes a high level and a low level
• (b) inputting, by a first optical path, said first signal light into a first distributed feedback (DFB) laser having a first output saturation characteristic, and adjusting, by the first DFB laser, the power of said first signal light so that amplitude fluctuations at said high level of said first signal light are suppressed in said first DFB laser;
• (c) inputting, by a second optical path, said second signal light into a second distributed feedback (DFB) laser having a second output saturation characteristic different from said first output saturation characteristic, and adjusting, by the second DFB laser, the power of said second signal light so that amplitude fluctuations at said high level of said second signal light are suppressed in said second DFB laser;
• and
• (d) combining, by the interferometer, first waveform-shaped light output from said first DFB laser according to said first output saturation characteristic and second waveform-shaped light output from said second DFB laser according to said second output saturation characteristic.

A device comprising:

• a distributed feedback (DFB) laser having a stop band defined as a range of wavelengths allowing laser oscillation;
• and
• a drive circuit supplying a drive current to said DFB laser so that said DFB laser oscillates at a first wavelength included in said stop band;
• wherein
• signal light having a second wavelength not included in said stop band being input into said DFB laser;
• said signal light includes a high level and a low level;
• and
• the power of said signal light is adjusted so that amplitude fluctuations at said high level of said signal light are suppressed in said DFB laser.

A device comprising:

• a first optical coupler dividing signal light into first signal light and second signal light, each of said first signal light and said second signal light including a high level and a low level;
• a first distributed feedback (DFB) laser into which said first signal light is to be input, said first DFB laser having a first output saturation characteristic, and adjusting, by the first DFB laser, the power of said first signal light so that amplitude fluctuations at said high level of said first signal light are suppressed in said first DFB laser;
• a second distributed feedback (DFB) laser into which said second signal light is to be input, said second DFB laser having a second output saturation characteristic different from said first output saturation characteristic, and adjusting, by the second DFB laser, the power of said second signal light so that amplitude fluctuations at said high level of said second signal light are suppressed in said second DFB laser;
• and
• a second optical coupler combining first waveform-shaped light output from said first DFB laser according to said first output saturation characteristic and second waveform-shaped light output from said second DFB laser according to said second output saturation characteristic.

A device comprising:

• an optical branch dividing signal light into first signal light and second signal light;
• a waveform shaper receiving said first signal light and performing waveform shaping of said first signal light received to output resultant waveform-shaped light;
• a clock regenerator receiving said second signal light and regenerating clock pulses according to said second signal light received;
• and
• an optical retiming section receiving said waveform-shaped light and said clock pulses and correcting the timing of said waveform-shaped light according to said clock pulses to output resultant regenerated signal light;
• said waveform shaper comprising:
• a distributed feedback (DFB) laser into which said first signal light is to be input, said DFB laser having a stop band defined as a range of wavelengths allowing laser oscillation;
• and
• a drive circuit supplying a drive current to said DFB laser so that said DFB laser oscillates at a first wavelength included in said stop band;
• said signal light having a second wavelength not included in said stop band.

A system comprising:

• an optical fiber transmission line transmitting signal light;
• and
• at least one optical repeater arranged along said optical fiber transmission line;
• each of said at least one optical repeater comprising:
• a distributed feedback (DFB) laser into which said signal light transmitted by said optical fiber transmission line is supplied, said DFB laser having a stop band defined as a range of wavelengths allowing laser oscillation;
• and
• a drive circuit supplying a drive current to said DFB laser so that said DFB laser oscillates at a first wavelength included in said stop band;
• said signal light having a second wavelength not included in said stop band, wherein said signal light includes a high level and a low level, and the power of said signal light is adjusted so that amplitude fluctuations at said high level of said signal light are suppressed in said DFB laser.

A system comprising:

• an optical fiber transmission line transmitting signal light;
• and
• an optical receiver connected to an output end of said optical fiber transmission line;
• said optical receiver comprising:
• a distributed feedback (DFB) laser into which said signal light transmitted by said optical fiber transmission line is supplied, said DFB laser having a stop band defined as a range of wavelengths allowing laser oscillation;
• and
• a drive circuit supplying a drive current to said DFB laser so that said DFB laser oscillates at a first wavelength included in said stop band;
• said signal light having a second wavelength not included in said stop band, wherein said signal light includes a high level and a low level, and the power of said signal light is adjusted so that amplitude fluctuations at said high level of said signal light are suppressed in said DFB laser.

A device comprising:

• a plurality of distributed feedback (DFB) lasers cascaded through respective optical filters so that signal light is passed therethrough;
• each of said DFB lasers having a stop band defined as a range of wavelengths allowing laser oscillation;
• and
• each of said DFB lasers being driven, by a corresponding drive circuit, so as to oscillate at a first wavelength included in said stop band;
• said signal light having a second wavelength not included in said stop band, wherein said signal light includes a high level and a low level, and the power of said signal light is set so that amplitude fluctuations at said high level of said signal light are suppressed in said DFB lasers.

A method comprising:

• providing, by a waveform shaper, a distributed feedback (DFB) laser including an output saturation characteristic;
• inputting, by said DFB laser, signal light into said DFB laser;
• and
• outputting, by said DFB laser, wavelength-shaped light obtained by waveform shaping of said signal light according to said output saturation characteristic, wherein said signal light including a high level and a low level and said inputting comprising adjusting, by the distributed feedback laser, the power of said signal light so that amplitude fluctuations at said high level of said signal light are suppressed In said DFB laser.

A method comprising:

• oscillating by a distributed feedback (DFB) laser at a first wavelength;
• inputting, by the DFB laser, signal light having a second wavelength different from said first wavelength into said DFB laser;
• and
• adjusting, by the DFB laser, the power of said signal light so that said signal light is subjected to waveform shaping in said DFB laser, said signal light including a high level and a low level;
• and the power of said signal light is adjusted so that amplitude fluctuations at said high level of said signal light are suppressed in said DFB laser.

A device comprising:

• a distributed feedback (DFB) laser;
• and
• a drive circuit supplying a drive current to said DFB laser so that said DFB laser oscillates at a first wavelength;
• signal light having a second wavelength different from said first wavelength being input into said DFB laser;
• the power of said signal light being adjusted so that said signal light is subjected to waveform shaping in said DFB lasers, said signal light including a high level and a low level, and the power of said signal light is adjusted so that amplitude fluctuations at said high level of said signal light are suppressed in said DFB laser.

An optical waveform shaping device comprising:

• a laser diode;
• current supplying means for supplying a current to said laser diode so that said laser diode emits laser light;
• and
• light inputting means for inputting light having a wavelength different from the wavelength of said laser light emitted from said laser diode, into said laser diode, said input light including a high level and a low level and the power of said input light is adjusted so that amplitude fluctuations at said high level of said signal light are suppressed in said laser diode.