Optical amplifier, optical communication system including the same, and optical fiber module included in the same

An optical amplifier disposed on an optical transmission line through which a plurality of channels of signals included in a predetermined wavelength band propagate, said optical amplifier comprising:

• a first branching device for tapping part of light including said signals propagating through said optical transmission line;
• a first light-receiving device for detecting a power of said part of light tapped by said first branching device;
• an amplification optical fiber for amplifying said signals;
• a pumping light source for supplying pumping light of a predetermined wavelength to said amplification optical fiber;
• a delay medium arranged between said first branching device and said amplification optical fiber;
• and
• a control system for carrying out automatic gain control, said control system monitoring said power of said part of light tapped by said first branching device through said first light-receiving device, and controlling said pumping light source so as to regulate a power of said pumping light in conformity to a power fluctuation of said tapped part of light;
• wherein said delay medium imparts a signal delay time which is identical to or longer than a response time of said control system from when said power fluctuation is detected until when said control of said pumping light source is started.

An optical amplifier disposed on an optical transmission line through which a plurality of channels of signals included in a predetermined wavelength band propagate, said optical amplifier comprising:

• a first branching device for tapping part of light including said signals propagating through said optical transmission line;
• a first light-receiving device for detecting a power of said part of light tapped by said first branching device;
• an amplification optical fiber for amplifying said signals;
• a pumping light source for supplying pumping light of a predetermined wavelength to said amplification optical fiber;
• a delay medium arranged between said first branching device and said amplification optical fiber;
• and
• a control system for carrying out automatic gain control, said control system controlling said pumping light source by monitoring said power of said part of light tapped by said first branching device through said first light-receiving device and regulating a power of said pumping light in conformity to a power fluctuation of said tapped part of light;
• wherein said delay medium imparts a signal delay time which is identical to or longer than a response time of said control system from when said power fluctuation is detected until when said control of said pumping light source is started,
• wherein said pumping light supplied from said pumping light source has a wavelength of 0.98 μm.

An optical amplifier, disposed on an optical transmission line through which a plurality of channels of signals included in a predetermined wavelength band propagate, said optical amplifier comprising:

• a first branching device for tapping part of light including said signals propagating through said optical transmission line;
• a first light-receiving device for detecting a power of said part of light tapped by said first branching device;
• an amplification optical fiber for amplifying said signals;
• a pumping light source for supplying pumping light of a predetermined wavelength to said amplification optical fiber;
• a delay medium arranged between said first branching device and said amplification optical fiber;
• and
• a control system for carrying out automatic gain control, said control system controlling said pumping light source by monitoring said power of said part of light tapped by said first branching device through said first light-receiving device and regulating a power of said pumping light in conformity to a power fluctuation of said tapped part of light;
• wherein said delay medium provides a signal delay time of at least 1 μs but not longer than 50 μs.

An optical amplifier disposed on an optical transmission line through which a plurality of channels of signals included in a predetermined wavelength band propagate, said optical amplifier comprising:

• a first branching device for tapping part of light including said signals propagating through said optical transmission line;
• a first light-receiving device for detecting a power of said part of light tapped by said first branching device;
• an amplification optical fiber for amplifying said signals;
• a pumping light source for supplying pumping light of a predetermined wavelength to said amplification optical fiber;
• a delay medium arranged between said first branching device and said amplification optical fiber;
• and
• a control system for carrying out automatic gain control, said control system controlling said pumping light source by monitoring said power of said part of light tapped by said first branching device through said first light-receiving device and regulating a power of said pumping light in conformity to a power fluctuation of said tapped part of light;
• wherein said delay medium includes a single-mode optical fiber having a length of at least 0.2 km but not longer than 10 km.

An optical amplifier disposed on an optical transmission line through which a plurality of channels of signals included in a predetermined wavelength band propagate, said optical amplifier comprising:

• a first branching device for tapping part of light including said signals propagating through said optical transmission line;
• a first light-receiving device for detecting a power of said part of light tapped by said first branching device;
• an amplification optical fiber for amplifying said signals;
• a pumping light source for supplying pumping light of a predetermined wavelength to said amplification optical fiber;
• a delay medium arranged between said first branching device and said amplification optical fiber;
• and
• a control system for carrying out automatic gain control, said control system controlling said pumping light source by monitoring said power of said part of light tapped by said first branching device through said first light-receiving device and regulating a power of said pumping light in conformity to a power fluctuation of said tapped part of light;
• wherein said signal delay time given by said delay medium is adjusted such that, in terms of a transient fluctuation of gain in said optical amplifier caused by a power fluctuation in light including said signals with respect to a target gain, said gain yields an overshoot amount and an undershoot amount which are substantially identical to each other.

An optical amplifier disposed on an optical transmission line through which a plurality of channels of signals included in a predetermined wavelength band propagate, said optical amplifier comprising:

• a first branching device for tapping part of light including said signals propagating through said optical transmission line;
• a first light-receiving device for detecting a power of said part of light tapped by said first branching device;
• an amplification optical fiber for amplifying said signals;
• a pumping light source for supplying pumping light of a predetermined wavelength to said amplification optical fiber;
• a delay medium arranged between said first branching device and said amplification optical fiber;
• and
• a control system for carrying out automatic gain control, said control system controlling said pumping light source by monitoring said power of said part of light tapped by said first branching device through said first light-receiving device and regulating a power of said pumping light in conformity to a power fluctuation of said tapped part of light;
• wherein said delay medium imparts a signal delay time which is identical to or longer than a response time of said control system from when said power fluctuation is detected until when said control of said pumping light source is started;
• wherein said control system carries out automatic gain control by utilizing a linear expression Pp=a·PIN+b (where a and b are constants) which provides a relationship between the power PIN of said part of light tapped by said first branching device and the power Pp of said pumping light outputted from said pumping light source.

An optical amplifier disposed on an optical transmission line through which a plurality of channels of signals included in a predetermined wavelength band propagate, said optical amplifier comprising:

• a first branching device for tapping part of light including said signals propagating through said optical transmission line;
• a first light-receiving device for detecting a power of said part of light tapped by said first branching device;
• an amplification optical fiber for amplifying said signals;
• a pumping light source for supplying pumping light of a predetermined wavelength to said amplification optical fiber;
• a delay medium arranged between said first branching device and said amplification optical fiber;
• and
• a control system for carrying out automatic gain control, said control system controlling said pumping light source by monitoring said power of said part of light tapped by said first branching device through said first light-receiving device and regulating a power of said pumping light in conformity to a power fluctuation of said tapped part of light, further comprising:
• a second branching device for tapping part of amplified light transmitted through said amplification optical fiber, and a second light-receiving device for detecting a power of said part of light tapped by said second branching device;
• wherein said control system monitors respective powers of parts of light tapped by said first and second branching devices and controls said pumping light source so as to regulate a power of said pumping light according to results of detection obtained by said first and second light-receiving devices.