Method and device for optical amplification and system having the device

A method comprising the steps of:

• (a) pumping an optical amplifying medium so that said optical amplifying medium provides a gain band including a first band giving a relatively high gain and noise figure to an optical signal and a second band giving a relatively low gain and noise figure to said optical signal;
• (b) supplying to said optical amplifying medium said optical signal passed through a first optical filter having characteristics such that said first optical filter suppresses wavelength dependence of gain in said second band;
• and
• (c) supplying said optical signal output from said optical amplifying medium to a second optical filter having characteristics such that said second optical filter suppresses wavelength dependence of gain in said first band.

A device comprising:

• an optical amplifying medium having an input end and an output end for an optical signal;
• means for pumping said optical amplifying medium so that said optical amplifying medium has substantially simple gain characteristics in a predetermined band, said substantially simple gain characteristic producing a gain tilt such that gain increases with an increase in wavelength;
• and
• an optical filter optically connected to at least one of said input end and said output end of said optical amplifying medium and having characteristics such that said optical filter suppresses wavelength dependence of gain in said predetermined band.

A device comprising:

• a doped fiber doped with a dopant including Er (erbium);
• means for pumping said doped fiber so that said doped fiber has a gain tilt such that the gain increases with an increase in wavelength in a predetermined band;
• and
• an optical filter operatively connected to said doped fiber and having a loss tilt such that said optical filter suppresses said gain tilt.

A system comprising:

• first and second terminal stations;
• an optical fiber transmission line connecting said first and second terminal stations;
• and
• at least one optical repeater provided in said optical fiber transmission line;
• said first terminal station comprising a plurality of optical senders for respectively outputting a plurality of optical signals having different wavelengths, and an optical multiplexer for wavelength division multiplexing said plurality of optical signals to obtain WDM optical signals and outputting said WDM optical signals to said optical fiber transmission line;
• said second terminal station comprising an optical demultiplexer for separating said WDM optical signals transmitted by said optical fiber transmission line into a plurality of optical signals, and a plurality of optical receivers for respectively receiving said plurality of optical signals;
• said optical repeater comprising an optical amplifier comprising an optical amplifying medium having an input end and an output end for an optical signal, and means for pumping said optical amplifying medium so that said optical amplifying medium provides a gain band including a first band giving a relatively high gain and noise figure to said optical signal and a second band giving a relatively low gain and noise figure;
• a first optical filter optically connected to said input end of said optical amplifying medium and having characteristics such that said first optical filter suppresses wavelength dependence of gain in said second band;
• and a second optical filter optically connected to said output end of said optical amplifying medium and having characteristics such that said second optical filter suppresses wavelength dependence of gain in said first band.

A system comprising:

• first and second terminal stations;
• an optical fiber transmission line connecting said first and second terminal stations;
• and
• at least one optical repeater provided in said optical fiber transmission line;
• said first terminal station comprising a plurality of optical senders for respectively outputting a plurality of optical signals having different wavelengths, and an optical multiplexer for wavelength division multiplexing said plurality of optical signals to obtain WDM optical signals and outputting said WDM optical signals to said optical fiber transmission line;
• said second terminal station comprising an optical demultiplexer for separating said WDM optical signals transmitted by said optical fiber transmission line into a plurality of optical signals, and a plurality of optical receivers for respectively receiving said plurality of optical signals;
• said optical repeater comprising an optical amplifying medium having an input end and an output end for an optical signal;
• means for pumping said optical amplifying medium so that said optical amplifying medium has substantially simple gain characteristics in a predetermined band, said substantially simple gain characteristics give a gain tilt such that the gain increases with an increase in wavelength;
• and an optical filter optically connected to at least one of said input end and said output end of said optical amplifying medium and having characteristics such that said optical filter suppresses wavelength dependence of gain in said predetermined band.

A system comprising:

• first and second terminal stations;
• an optical fiber transmission line connecting said first and second terminal stations;
• and
• at least one optical repeater provided in said optical fiber transmission line;
• said first terminal station comprising a plurality of optical senders for respectively outputting a plurality of optical signals having different wavelengths, and an optical multiplexer for wavelength division multiplexing said plurality of optical signals to obtain WDM optical signals and outputting said WDM optical signals to said optical fiber transmission line;
• said second terminal station comprising an optical demultiplexer for separating said WDM optical signals transmitted by said optical fiber transmission line into a plurality of optical signals, and a plurality of optical receivers for respectively receiving said plurality of optical signals;
• said optical repeater comprising a doped fiber doped with a dopant including Er (erbium);
• means for pumping said doped fiber so that said doped fiber has a gain tilt such that the gain increases with an increase in wavelength in a predetermined band;
• and an optical filter operatively connected to said doped fiber and having a loss tilt such that said optical filter suppresses said gain tilt.

A device comprising:

• an optical amplifier comprising an optical amplifying medium having an input end and an output end for an optical signal, and said optical amplifying medium being pumped so that said optical amplifying medium provides a gain band including a first band giving a relatively high gain and noise figure to said optical signal and a second band giving a relatively low gain and noise figure;
• a first optical filter optically connected to said input end of said optical amplifying medium and having characteristics such that said first optical filter suppresses wavelength dependence of gain in said second band;
• and
• a second optical filter optically connected to said output end of said optical amplifying medium and having characteristics such that said second optical filter suppresses wavelength dependence of gain in said first band.

A device comprising:

• an optical amplifying medium having an input end and an output end for an optical signal;
• a pumping unit pumping said optical amplifying medium so that said optical amplifying medium has substantially simple gain characteristics in a predetermined band, said substantially simple gain characteristic producing a gain tilt such that gain increases with an increase in wavelength;
• and
• an optical filter optically connected to at least one of said input end and said output end of said optical amplifying medium and having characteristics such that said optical filter suppresses wavelength dependence of gain in said predetermined band.

A device comprising:

• a doped fiber doped with a dopant including Er (erbium);
• a pumping unit to pump said doped fiber so that said doped fiber has a gain tilt such that the gain increases with an increase in wavelength in a predetermined band;
• and
• an optical filter operatively connected to said doped fiber and having a loss tilt such that said optical filter suppresses said gain tilt.

A system comprising:

• first and second terminal stations;
• an optical fiber transmission line connecting said first and second terminal stations;
• and
• at least one optical repeater provided in said optical fiber transmission line;
• said first terminal station comprising a plurality of optical senders for respectively outputting a plurality of optical signals having different wavelengths, and an optical multiplexer for wavelength division multiplexing said plurality of optical signals to obtain WDM optical signals and outputting said WDM optical signals to said optical fiber transmission line;
• said second terminal station comprising an optical demultiplexer for separating said WDM optical signals transmitted by said optical fiber transmission line into a plurality of optical signals, and a plurality of optical receivers for respectively receiving said plurality of optical signals;
• said optical repeater comprising an optical amplifier comprising an optical amplifying medium having an input end and an output end for an optical signal, and a pumping unit pumping said optical amplifying medium so that said optical amplifying medium provides a gain band including a first band giving a relatively high gain and noise figure to said optical signal and a second band giving a relatively low gain and noise figure;
• a first optical filter optically connected to said input end of said optical amplifying medium and having characteristics such that said first optical filter suppresses wavelength dependence of gain in said second band;
• and a second optical filter optically connected to said output end of said optical amplifying medium and having characteristics such that said second optical filter suppresses wavelength dependence of gain in said first band.

A system comprising:

• first and second terminal stations;
• an optical fiber transmission line connecting said first and second terminal stations;
• and
• at least one optical repeater provided in said optical fiber transmission line;
• said first terminal station comprising a plurality of optical senders for respectively outputting a plurality of optical signals having different wavelengths, and an optical multiplexer for wavelength division multiplexing said plurality of optical signals to obtain WDM optical signals and outputting said WDM optical signals to said optical fiber transmission line;
• said second terminal station comprising an optical demultiplexer for separating said WDM optical signals transmitted by said optical fiber transmission line into a plurality of optical signals, and a plurality of optical receivers for respectively receiving said plurality of optical signals;
• said optical repeater comprising an optical amplifying medium having an input end and an output end for an optical signal;
• a pumping unit pumping said optical amplifying medium so that said optical amplifying medium has substantially simple gain characteristics in a predetermined band, said substantially simple gain characteristics give a gain tilt such that the gain increases with an increase in wavelength;
• and an optical filter optically connected to at least one of said input end and said output end of said optical amplifying medium and having characteristics such that said optical filter suppresses wavelength dependence of gain in said predetermined band.

A system comprising:

• first and second terminal stations;
• an optical fiber transmission line connecting said first and second terminal stations;
• and
• at least one optical repeater provided in said optical fiber transmission line;
• said first terminal station comprising a plurality of optical senders for respectively outputting a plurality of optical signals having different wavelengths, and an optical multiplexer for wavelength division multiplexing said plurality of optical signals to obtain WDM optical signals and outputting said WDM optical signals to said optical fiber transmission line;
• said second terminal station comprising an optical demultiplexer for separating said WDM optical signals transmitted by said optical fiber transmission line into a plurality of optical signals, and a plurality of optical receivers for respectively receiving said plurality of optical signals;
• said optical repeater comprising a doped fiber doped with a dopant including Er (erbium);
• means for pumping said doped fiber so that said doped fiber has a gain tilt such that the gain increases with an increase in wavelength in a predetermined band;
• and an optical filter operatively connected to said doped fiber and having a loss tilt such that said optical filter suppresses said gain tilt.