Optical fiber amplifier doped with dysprosium ion for the 1.3 .mu.m wavelength band

An optical amplifier comprising:

• an excitation light source which radiates excitation light formed of semiconductor laser beams and includes a semiconductor laser module which is so modularized that the excitation light can be taken out of an output optical fiber;
• a coupler which includes an optical fiber coupler or an optical waveguide coupler to combine the excitation light and 1.3 .mu.m-band signal light radiated from the excitation light source;
• and
• an optical fiber comprising a higher-refractive-index area formed of an optical material doped with Dy ions having an electrovalence of three and a lower-refractive-index area, wherein output light radiated from the coupler is incident upon an incident portion of the optical fiber, is amplified, and is emitted from an emitting portion of the optical fiber.

An optical transmission system which comprises:

• an excitation light source which radiates excitation light formed of semiconductor laser beams and includes a semiconductor laser module which is so modularized that the excitation light can be taken out of an output optical fiber;
• a signal light source which radiates signal light formed of 1.3 .mu.m-band semiconductor laser beams with an oscillation wavelength range of 1.3-1.35 .mu.m and includes a semiconductor laser module which is so modularized that the signal light can be taken out of an output optical fiber;
• an electric signal source for feeding the signal light source with electric signals;
• a first coupler including an optical fiber coupler or an optical waveguide coupler to combine the excitation light radiated from the excitation light source with the signal light radiated from the signal light source;
• an optical fiber comprising a higher-refractive-index area formed of an optical material doped with Dy ions having an electrovalence of three and a lower-refractive-index area wherein output light radiated from the first coupler is amplified and is emitted;
• a second coupler including an optical fiber coupler or an optical waveguide coupler to divide the output light radiated from the optical fiber into excitation light and signal light;
• a distributor to distribute the signal light radiated from the second coupler;
• and
• a photodetector to receive the signal light distributed by the distributor.

A solid-state laser comprising:

• an excitation light source which radiates excitation light formed of 800 nm-band semiconductor laser beams with an oscillation wavelength range of 800-860 nm;
• an optical fiber comprising a higher-refractive-index area formed of an optical material doped with Dy ions having an electrovalence of three and a lower-refractive-index area, wherein the excitation light from the excitation light source is incident upon the optical fiber;
• an incident portion reflector which is provided at an incident portion of the optical fiber and has a high reflection index for light with a wavelength range of 800-1000 nm as well as for light with a wavelength range of 1200-1400 nm;
• and
• an emitting portion reflector that is provided at an emitting portion of the optical fiber and has a high reflection index for light with a wavelength range of 800-1000 nm while having an 80-99.5% reflection index for light with a wavelength range of 1200-1400 nm;
• wherein the incident portion reflector and the emitting portion reflector together constitute an optical resonator.