Abstract: To provide a process for producing an air cladding type optical fiber by a method other than extrusion molding. A process for producing an optical fiber comprising a hollow glass fiber with an optical transmission glass held to extend in its axial direction at its center, which process comprises a step of heating and drawing a glass rod having three or more holes with an equal diameter provided around its center axis to extend in its axial direction where the distance between each hole and the axis is mutually equal and the distance between adjacent holes is mutually equal, and a portion surrounded by such holes will constitute said optical transmission glass, while applying pressure to expand the holes with one end of the rod closed, to form a preform wherein glass between the holes is in a plate form, and subjecting the preform to wire drawing to form an optical fiber in which said optical transmission glass is held by plate glass.

Abstract: A nonlinear fiber having a third-order nonlinear coefficient of at least 30 W?1km?1, and its cladding containing Er or Tm at a portion within 3 ?m from the interface with its core. A wavelength conversion method of making a signal light having a wavelength ?S and an intensity IS and a pump light having a wavelength ?P which is shorter than 2?S and an intensity higher than IS enter a nonlinear fiber 1, and generating a converted light having a wavelength ?C of ?S?P/(2?S??P) and an intensity IC by four wave mixing, wherein Er or Tm is present in the cladding at a portion with a diameter in the nonlinear fiber 1 of at most the mode field diameter, and the converted light is generated by four wave mixing while Er or Tm is excited by an excitation light.

Abstract: A nonlinear fiber having a third-order nonlinear coefficient of at least 30 W?1km?1, and its cladding containing Er or Tm at a portion within 3 ?m from the interface with its core. A wavelength conversion method of making a signal light having a wavelength ?S and an intensity IS and a pump light having a wavelength ?P which is shorter than 2?S and an intensity higher than IS enter a nonlinear fiber 1, and generating a converted light having a wavelength ?C of ?S?P/(2?S??P) and an intensity IC by four wave mixing, wherein Er or Tm is present in the cladding at a portion with a diameter in the nonlinear fiber 1 of at most the mode field diameter, and the converted light is generated by four wave mixing while Er or Tm is excited by an excitation light.

Abstract: A non-lead optical glass consisting essentially of, as represented by mol %, from 45 to 75% of Bi2O3, from 12 to 45% of B2O3, from 1 to 20% of Ga2O3, from 1 to 20% of In2O3, from 0 to 20% of ZnO, from 0 to 15% of BaO, from 0 to 15% of SiO2+Al2O3+GeO2, from 0 to 15% of MgO+CaO+SrO, from 0 to 10% of SnO2+TeO2+TiO2+ZrO2+Ta2O3+Y2O3+WO3 and from 0 to 5% of CeO2, wherein Ga2O3+In2O3+ZnO?5%. An optical fiber comprising the above non-lead optical glass as a core.

Abstract: An optical amplifying glass comprising a matrix glass and from 0.001 to 10% by mass percentage of Tm doped to the matrix glass, wherein the matrix glass contains from 15 to 80 mol % of Bi2O3 and further contains at least one component selected from the group consisting of SiO2, B2O3 and GeO2.

Abstract: An optical amplifying glass comprising a matrix glass and from 0.001 to 10% by mass percentage of Tm doped to the matrix glass, wherein the matrix glass contains from 15 to 80 mol % of Bi2O3 and further contains at least one component selected from the group consisting of SiO2, B2O3 and GeO2.