# US 5,351,335 A · Optical fiber for optical amplifier > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,351,335 A - Document ID: US5351335A - Status: Granted - Kind: A - Application number: 07/934,242 - Filed: 1992-08-25 - Granted: 1994-09-27 - Earliest claimed: 1991-08-26 - Assignees: Nippon Telegraph and Telephone Corporation - Inventors: Yasutake Ohishi; Terutoshi Kanamori; Yoshiki Nishida; Atsushi Mori; Shoichi Sudo - Web page: https://patentgrep.com/patent/US5351335A ## CPC - H01S 3/06716: {Fibre compositions (per se C03C13/04)or doping with active elements (lasing materials in general H01S3/14)} - C03C 4/0071: {for laserable glass} - C03C 13/042: {Fluoride glass compositions} - H01S 3/1608: {erbium} - H01S 3/1611: {neodymium} - H01S 3/1613: {praseodymium} - H01S 3/1618: {ytterbium} - H01S 3/173: {fluoride glass, e.g. fluorozirconate or ZBLAN [ ZrF4-BaF2-LaF3-AlF3-NaF]} - H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL - C03C: CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS ## Abstract Fluoride glass-based optical fiber for an optical amplifier which contains rare earth metal ions in the core glass has a relative refractive index difference .DELTA..sub.n between the core and the cladding of 1.4% or more. The core glass contains PbF.sub.2 in a proportion of 25 mol % or less based on the total composition of the core glass . The fluoride glass is doped with rare earth metal ions, and part of the fluorine in the glass may be substituted by at least one halogen. Pr.sup.3+, Pr.sup.3+ --Yb.sup.3+, Pr.sup.3+ --Nd.sup.3+, or Pr.sup.3+ --Er.sup.3+ can be doped as the rare earth metal ions. Chlorine, bromine or iodine may be used as the halogen. ## Claims ### Claim 1 A fluoride glass optical fiber for an optical amplifier having a core and a cladding, and containing rare earth metal ions in a core glass, wherein the relative refractive index difference (.DELTA..sub.n) between the core and the cladding is at least 1.4%, and the core glass contains PbF.sub.2 in a proportion which is not greater than 25 mol % based on the total composition of the core glass. ### Claim 2 (depends on 1) The optical fiber as claimed in claim 1, wherein said core glass contains LiF in a proportion of 3 to 12 mol % and within the range (11-0.4x)<y<(15-0.4x) in which x represents the concentration of PbF.sub.2 (mol %) and y represents the concentration of LiF (mol %). ### Claim 3 (depends on 2) The optical fiber as claimed in claim 2, wherein said core contains a core matrix comprising a fluoride glass composed of 50 to 60 mol % of ZrF.sub.4, 7 to 25 mol % of PbF.sub.2, 6 to 19 mol % of BaF.sub.2, 1.5 to 6 mol % of LaF.sub.3, 0 to 4 mol % of at least one member selected from the group consisting of ScF.sub.3, YF.sub.3, GdF.sub.3 and LuF.sub.3, 1.5 to 5 mol % of AlF.sub.3, and 3 to 12 mol % of LiF, with the total amount of the components being 100 mol %. ### Claim 4 (depends on 1) The optical fiber as claimed in claim 1, wherein said core contains a core matrix comprising a fluoride glass composed of 10 to 40 mol % of InF.sub.3, 20 to 50 mol % of ZnF.sub.2, 6 to 30 mol % of BaF.sub.2, 5 to 15 mol % of SrF.sub.2, 0 to 25 mol % of PbF.sub.2, 0 to 7 mol % of CdF.sub.2, 1.5 to 6 mol % of at least one member selected from the group consisting of LaF.sub.3, ScF.sub.3, YF.sub.3, GdF.sub.3 and LuF.sub.3, 1.5 to 5 mol % of GaF.sub.3, and 2 to 10 mol % of LiF or NaF, with the total amount of the components being 100 mol %. ### Claim 5 (depends on 4) The optical fiber as claimed in claim 4, wherein said cladding contains a cladding matrix comprising a fluoride glass composed of 10 to 40 mol % of InF.sub.3, 20 to 50 mol % of ZnF.sub.2, 6 to 30 mol % of BaF.sub.2, 5 to 15 mol % of SrF.sub.2, 0 to 25 mol % of PbF.sub.2, 0 to 7 mol % of CdF.sub.2, 1.5 to 6 mol % of at least one member selected from the group consisting of LaF.sub.3, ScF.sub.3, YF.sub.3, GdF.sub.3 and LuF.sub.3, 1.5 to 5 mol % of AlF.sub.3 or GaF.sub.3, and 2 to 10 mol % of LiF or NaF, with the total amount of the components being 100 mol %. ### Claim 6 (depends on 4) The optical fiber as claimed in claim 4, wherein said cladding contains a cladding matrix comprising a fluoride glass composed of 43 to 55 mol % of at least one member selected from the group consisting of ZrF.sub.4 and HfF.sub.4, 18 to 28 mol % of BaF.sub.2, 1.5 to 6 mol % of LaF.sub.3, 0 to 4 mol % of one member selected from the group consisting of ScF.sub.3, YF.sub.3, GdF.sub.3 and LuF.sub.3, 1.5 to 5 mol % of AlF.sub.3, and 15 to 25 mol % of one member selected from the group consisting of LiF and NaF, with the total amount of the components being 100 mol %. ### Claim 7 (depends on 1) The optical fiber as claimed in claim 1, wherein said core contains a core matrix comprising a fluoride glass composed of 10 to 40 mol % of InF.sub.3, 20 to 50 mol % of ZnF.sub.2, 5 to 25 mol % of PbF.sub.2, 6 to 19 mol % of BaF.sub.2, 5 to 15 mol % of SrF.sub.2, 0 to 7 mol % of CdF.sub.2, 0 to 10 mol % of LaF.sub.3, 0 to 4 mol % at least one member selected from the group consisting of ScF.sub.3, YF.sub.3, GdF.sub.3 and LuF.sub.3, 0 to 5 mol % of AlF.sub.3, and 0 to 15 mol % of LiF or NaF, with the total amount of the components being 100 mol %. ### Claim 8 (depends on 7) The optical fiber as claimed in claim 7, wherein said cladding contains a cladding matrix comprising a fluoride glass composed of 10 to 40 mol % of InF.sub.3, 20 to 50 mol % of ZnF.sub.2, 5 to 25 mol % of PbF.sub.2, 6 to 19 mol % of BaF.sub.2, 5 to 15 mol % of SrF.sub.2, 0 to 7 mol % of CdF.sub.2, 0 to 10 mol % of LaF.sub.3, 0 to 4 mol % of at least one member selected from the group consisting of ScF.sub.3, YF.sub.3, GdF.sub.3 and LuF.sub.3, 0 to 5 mol % of AlF.sub.3, and 0 to 15 mol % of LiF or NaF, with the total amount of the components being 100 mol %. ### Claim 9 (depends on 7) The optical fiber as claimed in claim 7, wherein said fluoride glass constituting the cladding glass matrix comprises 43 to 55 mol % of at least one member selected from the group consisting of ZrF.sub.4 and HfF.sub.4, 18 to 28 mol % of BaF.sub.2, 1.5 to 6 mol % of LaF.sub.3, 0 to 4 mol % of one member selected from the group consisting of ScF.sub.3, YF.sub.3, GdF.sub.3 and LuF.sub.3, 1.5 to 5 mol % of AlF.sub.3, and 15 to 25 mol % of one member selected from the group consisting of LiF and NaF, with the total amount of the components being 100 mol %. ### Claim 10 (depends on 1) The optical fiber as claimed in claim 1, wherein said rare earth metal ions are one member selected from the group consisting of Pr.sup.3+, Pr.sup.3+ --Yb.sup.3+, Pr.sup.3+ --Nd.sup.3+, and Pr.sup.3+ --Er.sup.3+. ### Claim 11 A fluoride glass optical fiber for an optical amplifier, having a core and a cladding and containing rare earth metal ions in a core glass, wherein said fluoride glass is an InF.sub.3 glass, and wherein part of the fluoride in the fluoride glass is substituted by at least one halogen other than fluoride. ### Claim 12 (depends on 11) The optical fiber as claimed in claim 11, wherein said rare earth metal ions are selected from the group consisting of Pr.sup.3+, Pr.sup.3+ --Yb.sup.3+, Pr.sup.3+ --Nd.sup.3+, and Pr.sup.3+ --Er.sup.3+. ### Claim 13 (depends on 11) The optical fiber as claimed in claim 11, wherein said halogen is chlorine, bromine or iodine. ### Claim 14 (depends on 12) The optical fiber as claimed in claim 12, wherein said halogen is chlorine, bromine or iodine. ### Claim 15 (depends on 1) The optical fiber as claimed in claim 1, wherein said core has a core radius which is not greater than 1.95 .mu.m. ### Claim 16 A fluoride glass optical fiber, for an optical amplifier having a core and a cladding and containing rare earth metal ions in a core glass, wherein part of the fluoride in the fluoride glass is substituted by at least one halogen other than fluoride, and wherein said core has a core radius which is not greater than 1.95 .mu.m. ### Claim 17 (depends on 12) The optical fiber as claimed in claim 12, wherein said core has a core radius which is not greater than 1.95 .mu.m. ### Claim 18 (depends on 10) The optical fiber as claimed in claim 10, wherein said core has a core radius which is not greater than 1.95 .mu.m. ### Claim 19 (depends on 1) The optical fiber as claimed in claim 1, wherein the relative refractive index difference between the core and the cladding is at least 2.5%. ### Claim 20 (depends on 16) The optical fiber as claimed in claim 16, wherein said fluoride glass is an InF.sub.3 glass. ### Claim 21 A fluoride glass optical fiber for an optical amplifier, having a core and a cladding and containing rare earth metal ions in a core glass, wherein part of the fluoride in the fluoride glass is substituted by at least one halogen other than fluoride, and wherein said fluoride glass is a ZrF.sub.4 glass which contains a Ba halide, the halide in said Ba halide being chloride, bromide or iodide. ### Claim 22 (depends on 16) The optical fiber as claimed in claim 16, wherein said fluoride glass is a ZrF.sub.4 glass. ### Claim 23 (depends on 16) The optical fiber as claimed in claim 16, wherein said ZrF.sub.4 glass contains Ba halide, the halide in said Ba halide being chloride, bromide or iodide.