Optical fiber amplifier and optical amplification method

An optical amplifier, comprising:

• a fiber having a core part and a clad part, in which the fiber is comprised of silica as a main component, and at least one of the core part and the clad part of the fiber is doped with erbium;
• a 0.98 μm excitation light source for exciting 4I{fraction (11/2)} level of Er in said fiber;
• optical means for inputting excitation light from said excitation light source and signal light to said fiber;
• and
• an optical isolator,
• wherein a product of a fiber length of said fiber and an erbium concentration in said fiber is greater than 0.3×105 (m·wt.ppm).

An optical amplifier, comprising:

• a fiber having a core part and a clad part, in which the fiber is comprised of silica as a main component, and at least one of the core part and the clad part of the fiber is doped with erbium;
• a 1.48 μm excitation light source for exciting a 4I{fraction (13/2)} level of Er in said fiber;
• optical means for inputting excitation light from said excitation light source and signal light to said fiber;
• and
• an optical isolator,
• wherein a product of a fiber length of said fiber and an erbium concentration in said fiber is greater than 0.6×105 (m·wt.ppm).

An optical amplifier, comprising:

• an erbium-doped fluoride base fiber having a core part and a clad part, at least one of the core part and the clad part being doped with erbium;
• a 0.97 μm excitation light source for exciting a 4I{fraction (11/2)} level of Er in said fluoride base fiber;
• optical means for inputting excitation light from said excitation light source and signal light to said fluoride base fiber;
• and
• an optical isolator,
• wherein a product of a fluoride base fiber length of said fluoride base fiber and an erbium concentration in said fluoride base fiber is greater than 0.1×105 (m·wt.ppm).

An optical amplifier, comprising:

• an erbium-doped fluoride base fiber having a core part and a clad part, at least one of the core part and the clad part being doped with erbium;
• a 1.48 μm excitation light source for exciting a 4I{fraction (13/2)} level of Er in said fluoride base fiber;
• optical means for inputting excitation light from said excitation light source and signal light to said fluoride base fiber;
• and
• an optical isolator,
• wherein a product of a fluoride base fiber length of said fluoride base fiber and an erbium concentration in said fluoride base fiber is greater than 0.2×105 (m wt.ppm).

An optical amplifier, comprising:

• a fiber having a core part and a clad part, in which the fiber is comprised of tellurite glass as a main component, and at least one of the core part and the clad part of the fiber is doped with erbium;
• a 0.98 μm excitation light source for exciting a 4I{fraction (11/2)} level of Er in said fiber;
• optical means for inputting excitation light from said excitation light source and signal light to said fiber;
• and
• an optical isolator,
• wherein a product of a fiber length of said fiber and an erbium concentration in said fiber is greater than 0.005×105 (m·wt.ppm).

An optical amplifier, comprising:

• a fiber having a core part and a clad part, in which the fiber is comprised of tellurite glass as a main component, and at least one of the core part and the clad part of the fiber is doped with erbium;
• a 1.48 μm excitation light source for exciting a 4I{fraction (13/2)} level of Er in said fiber;
• optical means for inputting excitation light from said excitation light source and signal light to said fiber;
• and
• an optical isolator,
• wherein a product of a fiber length of said fiber and an erbium concentration in said fiber is greater than 0.01×105 (m. wt.ppm).

An optical amplifier, comprising:

• a fiber having a core part and a clad part, in which the fiber is comprised of multi-component oxide glass as a main component, and at least one of the core part and the clad part of the fiber is doped with erbium;
• a 0.98 μm excitation light source for exciting a 4I{fraction (11/2)} level of Er in said fiber;
• optical means for inputting excitation light from said excitation light source and signal light to said fiber;
• and
• an optical isolator,
• wherein a product of a fiber length of said fiber and an erbium concentration in said fiber is greater than 0.008×105 (m·wt.ppm).

An optical amplifier, comprising:

• a fiber having a core part and a clad part, in which the fiber is comprised of multi-component oxide glass as a main component, and at least one of the core part and the clad part of the fiber is doped with erbium;
• a 1.48 μm excitation light source for exciting a 4I{fraction (13/2)} level of Er in said fiber;
• optical means for inputting excitation light from said excitation light source and signal light to said fiber;
• and
• an optical isolator,
• wherein a product of a fiber length of said fiber and an erbium concentration in said fiber is greater than 0.015×105 (m·wt.ppm).

An optical amplifier, comprising:

• a fiber having a core part and a clad part, in which the fiber is comprised of chalcogenide glass as a main component, and at least one of the core part and the clad part of the fiber is doped with erbium;
• a 0.98 μm excitation light source for exciting a 4I{fraction (11/12)} level of Er in said fiber;
• optical means for inputting excitation light from said excitation light source and signal light to said fiber;
• and
• an optical isolator,
• wherein a product of a fiber length of said fiber and an erbium concentration in said fiber is greater than 0.01×105 (m·wt.ppm).

An optical amplifier, comprising:

• a fiber having a core part and a clad part, in which the fiber is comprised of chalcogenide glass as a main component, and at least one of the core part and the clad part of the fiber is doped with erbium;
• a 1.48 μm excitation light source for exciting a 4I{fraction (13/2)} level of Er in said fiber;
• optical means for inputting excitation light from said excitation light source and signal light to said fiber;
• and
• an optical isolator,
• wherein a product of a fiber length of said fiber and an erbium concentration in said fiber is greater than 0.02×105 (m·wt.ppm).

An optical amplifier, comprising:

• a fiber having a core part and a clad part, in which the fiber is comprised of fluorophosphate glass as a main component, and at least one of the core part and the clad part of the fiber is doped with erbium;
• a 0.98 μm excitation light source for exciting a 4I{fraction (11/2)} level of Er in said fiber;
• optical means for inputting excitation light from said excitation light source and signal light to said fiber;
• and
• an optical isolator,
• wherein a product of a fiber length of said fiber and an erbium concentration in said fiber is greater than 0.008×105 (m·wt.ppm).

An optical amplifier, comprising:

• a fiber having a core part and a clad part, in which the fiber is comprised of fluorophosphate glass as a main component, and at least one of the core part and the clad part of the fiber is doped with erbium;
• a 1.48 μm excitation light source for exciting a 4I{fraction (13/2)} level of Er in said fiber;
• optical means for inputting excitation light from said excitation light source and signal light to said fiber;
• and
• an optical isolator,
• wherein a product of a fiber length of said fiber and an erbium concentration in said fiber is greater than 0.015×105 (m·wt.ppm).

An optical amplifier, comprising:

• a fiber having a core part and a clad part, in which the fiber is comprised of silica as a main component, and at least one of the core part and the clad part of the fiber is doped with erbium;
• a 0.98 μm excitation light source for exciting a 4I{fraction (11/2)} level of Er in said fiber and a 1.48 μm excitation light source for exciting a 4I{fraction (13/2)} level of Er in said fiber;
• optical means for inputting excitation light from said excitation light source and signal light to said fiber;
• and
• an optical isolator,
• wherein a product of a fiber length of said fiber and an erbium concentration in said fiber is greater than 0.01×105 (m·wt.ppm).

An optical amplifier, comprising:

• an erbium-doped fluoride base fiber having a core part and a clad part, at least one of the core part and the clad part being doped with erbium;
• a 0.97 μm excitation light source for exciting a 4I{fraction (11/2)} level of Er in said fluoride base fiber and a 1.48 μm excitation light source for exciting a 4I{fraction (13/2)} level of Er in said fluoride base fiber;
• optical means for inputting excitation light from said excitation light source and signal light to said fluoride base fiber;
• and
• an optical isolator,
• wherein a product of a fluoride base fiber length of said fluoride base fiber and an erbium concentration in said fluoride base fiber is greater than 0.1×105 (m·wt.ppm).

An optical amplifier, comprising:

• a fiber having a core part and a clad part, in which the fiber is comprised of tellurite glass as a main component, and at least one of the core part and the clad part of the fiber is doped with erbium;
• a 0.98 μm excitation light source for exciting a 4I{fraction (11/2)} level of Er in said fiber and a 1.48 μm excitation light source for exciting a 4I{fraction (13/2)} level of Er in said fiber;
• optical means for inputting excitation light from said excitation light source and signal light to said fiber;
• and
• an optical isolator,
• wherein a product of fiber length of said fiber and erbium concentration in said fiber is greater than 0.005×105 (m·wt.ppm).

An optical amplifier, comprising:

• a fiber having a core part and a clad part, in which the fiber is comprised of multi-component oxide glass as a main component, and at least one of the core part and the clad part of the fiber is doped with erbium;
• a 0.98 μm excitation light source for exciting a 4I{fraction (11/2)} level of Er in said fiber and a 1.48 μm excitation light source for exciting a 4I{fraction (13/2)} level of Er in said fiber;
• optical means for inputting excitation light from said excitation light source and signal light to said fiber;
• and
• an optical isolator,
• wherein a product of fiber length of said fiber and erbium concentration in said fiber is greater than 0.008×105 (m·wt.ppm).

An optical amplifier, comprising:

• a fiber having a core part and a clad part, in which the fiber is comprised of chalcogenide glass as a main component, and at least one of the core part and the clad part of the fiber is doped with erbium;
• 0.98 μm excitation light source for exciting a 4I{fraction (11/2)} level of Er in said fiber and a 1.48 μm excitation light source for exciting a 4I{fraction (13/2)} level of Er in said fiber;
• optical means for inputting excitation light from said excitation light source and signal light to said fiber;
• and
• n optical isolator,
• wherein a product of fiber length of said fiber and erbium concentration in said fiber is greater than 0.01×105 (m·wt.ppm).

An optical amplifier, comprising:

• a fiber having a core part and a clad part, in which the fiber is comprised of fluorophosphate glass as a main component, and at least one of the core part and the clad part of the fiber is doped with erbium;
• a 0.98 μm excitation light source for exciting a 4I{fraction (11/2)} level of Er in said fiber and a 1.48 μm excitation light source for exciting a 4I{fraction (13/2)} level of Er in said fiber;
• optical means for inputting excitation light from said excitation light source and signal light to said fiber;
• and
• an optical isolator,
• wherein a product of fiber length of said fiber and erbium concentration in said fiber is greater than 0.008×105 (m·wt.ppm).

An optical amplification method for amplifying signal light in a wavelength region of 1.58 μm band comprising steps of:

• inputting signal light;
• dividing the signal light into a plurality of wavelength regions by demultiplexer;
• amplifying the divided signal lights by a plurality of optical amplification units;
• and
• combining the amplified divided signal lights outputted from said plurality of optical amplification units;
• wherein at least one of said optical amplification unit comprises an erbium-doped fiber having core part and a clad part, at least one of the core part and the clad part being doped with erbium, an excitation light source for exciting said Er-doped fiber, optical means for inputting an excitation light from said excitation light source and the individual divided signal light into said Er-doped fiber,
• an emission wavelength of said excitation light is selected from about 0.97, 0.98 or 1.48 μm, and
• the Er-doped fiber is selected to have a certain value of a product of an erbium-doped fiber length and an erbium concentration in said erbium-doped fiber so as to obtain a predetermined gain at a wavelength region of 1.58 μm-band.