Photonic band gap fiber and method of producing the same

Abstract

A photonic band gap fiber is provided having multiple air holes in a silica portion extending in the longitudinal direction of the fiber. The fiber includes a cladding containing an air hole periodic structure in an extended triangular lattice configuration, wherein first rows each having a number of air holes at a first pitch are arranged alternately in the cross section of the fiber with multiple second rows of air holes each with multiple air holes at a second pitch which is twice the first pitch. The fiber further includes an air hole core.

1 . A photonic band gap fiber comprising:
 silica portions;   multiple air holes, provided in the silica portions, extending in a longitudinal direction of the fiber; and   a cladding having an air hole periodic structure in an extended triangular lattice configuration in the cross section of the fiber;   wherein first rows each having a number of air holes at a first pitch, and second rows each having a plurality of air holes at a second pitch which is twice the first pitch, are arranged such that the air holes of the first rows are disposed alternately with the air holes of the second rows, and wherein the first rows and the second rows are arranged so as to form the extended triangular lattice configuration in the cross section of the fiber; and   the fiber further comprises an air hole core.   
   
   
       2 . The photonic band gap fiber according to  claim 1 , wherein the air hole core has a substantially circular shape in the cross section of the fibers, and a diameter D of the air hole core has a relationship of 0.7Λ≦D≦3.3Λ with respect to the first pitch Λ. 
   
   
       3 . The photonic band gap fiber according to  claim 1 , wherein the air hole core has a substantially circular shape in the cross section of the fiber and a diameter D of the air hole core has a relationship of 4.7Λ≦D≦7.3Λ with respect to the first pitch Λ. 
   
   
       4 . The photonic band gap fiber according to  claim 1 , wherein the air hole core has a substantially circular shape in the cross section of the fiber and a diameter D of the air hole core has a relationship of 8.7Λ≦D≦11.3Λ with respect to the first pitch Λ. 
   
   
       5 . The photonic band gap fiber according to  claim 1 , wherein the air holes each have a circular cross section and a diameter d circular shape that satisfies a relationship 0.85Λ≦d≦Λ with respect to the first pitch Λ. 
   
   
       6 . The photonic band gap fiber according to  claim 1 , wherein three or more layers of the air hole periodic structure in the extended triangular lattice configuration in the cladding are provided outside the air hole core. 
   
   
       7 . The photonic band gap fiber according to  claim 1 , having a core mode in which 60% or more of a transmitting power is concentrated in the air hole core region, and having optical characteristics wherein a surface mode is substantially absent. 
   
   
       8 . The photonic band gap fiber according to  claim 1 , having an optical characteristic wherein only a single core mode (where the number of modes in case of all degraded modes is taken as 1) is present. 
   
   
       9 . The photonic band gap fiber according to  claim 1 , having an optical characteristic wherein a core mode is present when a wavelength λ, transmitted in the fiber, satisfies a range of 0.7≦Γ/λ≦1.2 (where Γ=2Λ, and Λ is the first pitch). 
   
   
       10 . The photonic band gap fiber according to  claim 1 , having an optical characteristic wherein a core mode is present when a wavelength λ, transmitted in the fiber, satisfies a range of 1.4≦Γ/λ≦1.8 (where Γ=2Λ, and Λ is the first pitch). 
   
   
       11 . A method of producing a photonic band gap fiber, the method comprising:
 arranging silica capillary tubes and silica rods into first rows of air holes and into second rows of air holes, wherein in each first row, a number of capillary tubes are arranged at a first pitch, and in each second row capillary tubes and silica rods are alternately arranged, such that a capillary tube arrangement of a cross section forms an extended triangular lattice;   forming an air hole core region with capillary tube bundles containing silica rods by eliminating a central silica rod or by eliminating a central silica rod together with capillary tubes and silica rods surrounding the central silica rod;   heating the capillary tube bundles containing the silica rods and making them integrated thus forming a preform for fiber spinning; and   spinning the preform.   
   
   
       12 . The method of producing a photonic band gap fiber according to  claim 11 , wherein
 the capillary tubes have annular cross sections;   the silica rods have circular cross sections with diameters equal to diameters of the capillary tubes.   
   
   
       13 . The method of producing a photonic band gap fiber according to  claim 11 , wherein spinning the preform comprises making the capillary tube bundle containing silica rods integrated while it is inserted in a hole of a silica tube. 
   
   
       14 . The method of producing a photonic band gap fiber according to  claim 11 , wherein forming an air hole core region comprises eliminating only one silica rod at a center of the cross section of the capillary tube bundle containing silica rods. 
   
   
       15 . The method of producing a photonic band gap fiber according to  claim 11 , wherein forming an air hole core region comprises eliminating one silica rod at a center of the cross section of the capillary tube bundle containing silica rods, and capillary tubes and silica rods in no less than one layer and no more than five layers surrounding the central silica rod. 
   
   
       16 . The photonic band gap fiber according to  claim 10 , wherein the capillary tube bundle containing silica rods is provided such that the air hole periodic structure in the extended triangular lattice configuration surrounding the air hole core region has three or more layers of silica rods. 
   
   
       17 . A photonic band gap fiber having multiple air holes provided in silica portions extending in a longitudinal direction of the fiber, the fiber comprising:
 a cladding having an air hole periodic structure in an extended triangular lattice configuration in a cross section of the fiber wherein first rows each having a number of air holes at a first pitch, and second rows each having a plurality of air holes at a second pitch which is twice the first pitch, are arranged such that the air holes of the first rows alternate with the air holes of the second rows so as to form a triangular lattice in the cross section of the fiber; and   an air hole core comprising multiple air holes arranged at a constant pitch in a triangular lattice configuration.   
   
   
       18 . The photonic band gap fiber according to  claim 17 , wherein the core comprises an air hole at a center of the fiber cross section and a first layer of air holes surrounding the air hole at the center of the fiber. 
   
   
       19 . The photonic band gap fiber according to  claim 17 , wherein the core comprises an air hole at a center of the fiber cross section and two or more layers of air holes surrounding the air hole at the center of the fiber. 
   
   
       20 . The photonic band gap fiber according to  claim 17 , wherein a cross section of each of the air holes is circular and a diameter d of each of the air holes satisfies a relationship 0.85Λ≦d≦Λ with respect to the first pitch Λ. 
   
   
       21 . The photonic band gap fiber according to  claim 17 , wherein three or more layers of the air hole periodic structure in the extended triangular lattice configuration in the cladding are provided outside the core. 
   
   
       22 . The photonic band gap fiber according to  claim 17  having a core mode in which 60% or more of a transmitting power is concentrated in the core region, and optical characteristics wherein a surface mode is substantially absent. 
   
   
       23 . The photonic band gap fiber according to  claim 17 , having an optical characteristic wherein only a single core mode (where the number of modes in case of all degraded modes is taken as 1) is present. 
   
   
       24 . The photonic band gap fiber according to  claim 17 , having an optical characteristic wherein a core mode is present when a wavelength λ, transmitted in the fiber, satisfies a range of 0.7≦Γ/λ≦1.2 (where Γ=2Λ, and Λ is a first pitch). 
   
   
       25 . The photonic band gap fiber according to  claim 17 , having an optical characteristic wherein a core mode is present within a range in which a wavelength λ, transmitted in the fiber, satisfies a range of 1.4≦Γ/λ≦1.8 (where Γ=2Λ, and Λ is a first pitch). 
   
   
       26 . A method of producing a photonic band gap fiber, the method comprising:
 arranging silica capillary tubes and silica rods into first rows of air holes and into second rows of air holes, wherein each first row comprises a number of capillary tubes arranged at a first pitch, and each second row comprises capillary tubes and silica rods alternately arranged, such that a capillary tube arrangement of a cross section of the fiber forms an extended triangular lattice;   forming an air hole core region with capillary tube bundles containing silica rods by eliminating a central silica rod, or by eliminating the central silica rod together with capillary tubes and silica rods surrounding the central silica rod;   heating the capillary tube bundles containing the silica rods and making them integrated thus forming a preform for fiber spinning; and   spinning the preform.   
   
   
       27 . The method of producing a photonic band gap fiber according to  claim 26 , wherein
 the capillary tubes each have an annular cross section;   the silica rode each have a circular cross section with a diameter equal to diameters of the capillary tubes.   
   
   
       28 . The method of producing a photonic band gap fiber according to  claim 26 , wherein making the capillary tube bundles containing the silica rods integrated comprises making the capillary tube bundles containing silica rods integrated while they are inserted in a hole of a silica tube. 
   
   
       29 . The method of producing a photonic band gap fiber according to  claim 26 , wherein forming an air hole core region comprises replacing only one silica rod at a center of the capillary tube bundle containing silica rods with a capillary tube. 
   
   
       30 . The method of producing a photonic band gap fiber according to  claim 26 , wherein forming an air hole core region comprises replacing one silica rod at a center of the capillary tube bundle containing silica rods and one layer of silica rods surrounding the silica rod at the center of the capillary tube bundle, with capillary tubes. 
   
   
       31 . The method of producing a photonic band gap fiber according to  claim 26 , wherein forming an air hole core region comprises replacing one silica rod at a center of the capillary tube bundle containing silica rods and two layers of silica rods surrounding the silica rod at the center of the capillary tube bundle, with capillary tubes. 
   
   
       32 . The method of producing the photonic band gap fiber according to  claim 26 , wherein the capillary tube bundle containing silica rods is provided such that the air hole periodic structure in the extended triangular lattice configuration surrounding the air hole core region has three or more layers of silica rods. 
   
   
       33 . A photonic band gap fiber with multiple air holes provided in silica portions along a longitudinal direction of the fiber, the fiber comprising:
 multiple hexagonally-shaped silica portions at constant pitch Γ in a cross section of the fiber arranged in a triangular lattice configuration;   air holes disposed between the silica portions;   a cladding having a periodic structure wherein a length ω r  between two sides facing each other of the silica portion is equal to a length Λ which is half of the pitch Γ; and   an air hole core or a core with multiple hexagonal air holes arranged in triangular lattice configuration.   
   
   
       34 . A photonic band gap fiber with multiple air holes provided in silica portions extending in a longitudinal direction of the fiber, the fiber comprising:
 a cladding having an air hole periodic structure in an extended triangular lattice configuration wherein a length ω r  between two sides facing each other of the silica portion is substantially equal to a first pitch Λ, wherein first rows of air holes each comprising multiple hexagonal air holes at the first pitch Λ is arranged through a silica partition wall in a cross section of the fiber, and second rows of air holes each comprising multiple hexagonal air holes at a second pitch Γ, which is twice the first pitch, are arranged through hexagonally-shaped silica portions such that the air holes of the first rows are disposed alternately with the air holes of the second rows, so as to form a triangular lattice in a cross section of the fiber; and   an air hole core or core comprising multiple hexagonal air holes arranged in a triangular lattice configuration.   
   
   
       35 . The photonic band gap fiber according to  claim 34 , wherein a thickness ω b  of the silica partitioning wall is in a range of 0.005Λ≦ω b ≦0.2Λ. 
   
   
       36 . The photonic band gap fiber according to  claim 33  or  34 , wherein a diameter D of the air hole core has a relationship of 0.7Λ≦D≦3.3Λ with respect to the first pitch Λ. 
   
   
       37 . The photonic band gap fiber according to  claim 33  or  34 , wherein a diameter D of the air hole core has a relationship of 4.7Λ≦D≦7.3Λ with respect to the first pitch Λ. 
   
   
       38 . The photonic band gap fiber according to  claim 33  or  34 , wherein a diameter D of the air hole core has a relationship of 8.7Λ≦D≦11.3Λ with respect to the first pitch Λ. 
   
   
       39 . The photonic band gap fiber according to  claim 33  or  34 , wherein three or more layers of the air hole periodic structure in the extended triangular lattice configuration in the cladding are provided outside the core. 
   
   
       40 . The photonic band gap fiber according to  claim 33  or  34 , having a core mode in which 60% or more of a transmitting power is concentrated in the air hole core region, and optical characteristics wherein a surface mode is substantially absent. 
   
   
       41 . The photonic band gap fiber according to  claim 33  or  34 , having an optical characteristic wherein only a single core mode (where the number of modes in case of all degraded modes is taken as 1) is present. 
   
   
       42 . The photonic band gap fiber according to  claim 33  or  34 , having an optical characteristic wherein a core mode is present within a range in which a wavelength λ, transmitted in the fiber, satisfies a range of 0.6≦Γ/λ≦1.5. 
   
   
       43 . The photonic band gap fiber according to  claim 33  or  34 , having an optical characteristic wherein a core mode is present within a range in which a wavelength λ, transmitted in the fiber, satisfies a range of 1.4≦Γ/λ≦2.3. 
   
   
       44 . The photonic band gap fiber according to  claim 33  or  34 , having an optical characteristic wherein a core mode is present when a wavelength λ, transmitted in the fiber, satisfies a range of 2.2≦Γ/λ≦3.2. 
   
   
       45 . A method of producing a photonic band gap fiber, the method comprising:
 arranging silica capillary tubes and silica rods into first rows of air holes and into second rows of air holes, wherein each first row comprises multiple capillary tubes, and each second row comprises capillary tubes and the silica rods alternately arranged, such that the capillary tube arrangement of a cross section of the fiber forms an extended triangular lattice;   forming an air hole core region by
 eliminating a central silica rod or 
 eliminating the central silica rod together with capillary tubes and silica rods surrounding the central silica rod, or 
 forming a capillary tube bundle containing silica rods creating a capillary core region by replacing the central silica rod with capillary tubes; 
   heating the arrangement of capillary tubes and silica rods and making it integrated thus forming a preform for fiber spinning while maintaining a pressure in the spaces in the capillary tubes at a higher level than a pressure in spaces surrounding the capillary tubes; and   spinning the preform.   
   
   
       46 . The method of producing a photonic band gap fiber according to  claim 45 , wherein
 the capillary tubes have annular cross sections;   the silica rods have circular cross sections with diameters equal to those of the capillary tubes.   
   
   
       47 . The method of producing a photonic band gap fiber according to  claim 45 , wherein making the arrangement of capillary tubes and silica rods integrated comprises making the arrangement integrated while it is inserted in a hole of a silica tube. 
   
   
       48 . The method of producing a photonic band gap fiber according to  claim 47 , wherein only a pressure in the spaces in the capillary tubes in the arrangement inserted in the air hole of the silica tube is maintained at or above the atmospheric pressure, and spaces other than the spaces in the capillary tubes are maintained in a low pressure condition when performing the integration. 
   
   
       49 . The method of producing a photonic band gap fiber according to  claim 45 , wherein forming the air hole core region comprises eliminating one silica rod at a center of a cross section of the arrangement of capillary tubes and silica rods. 
   
   
       50 . The method of producing a photonic band gap fiber according to  claim 45 , wherein forming the air hole core region comprises eliminating one silica rod at the center of a cross section of the arrangement of capillary tubes and silica rods and capillary tubes and silica rods in no less than one layer and no more than five layers surrounding the central silica rod. 
   
   
       51 . The method of producing a photonic band gap fiber according to  claim 45 , wherein forming the air hole core region comprises replacing one silica rod at the center of a cross section of the arrangement of capillary tubes and silica rods with a capillary tube. 
   
   
       52 . The method of producing a photonic band gap fiber according to  claim 45 , wherein forming the air hole core regions comprises replacing one silica rod at the center of a cross section of the arrangement of capillary tubes and silica rods, and silica rods and capillary tubes surrounding the silica rod at the center, with a capillary tube. 
   
   
       53 . The method of producing the photonic band gap fiber according to  claim 45 , wherein the arrangement of capillary tubes and silica rods is provided such that the air hole periodic structure in the extended triangular lattice configuration surrounding the core region has three or more layers of silica rods. 
   
   
       54 . A photonic band gap fiber with multiple air holes in silica portions extending in a longitudinal direction of the fiber, the fiber comprising:
 multiple hexagonally-shaped silica portions at a constant pitch Γ in a cross section of the fiber arranged in a triangular lattice configuration;   air holes between the silica portions;   a cladding having a periodic structure wherein a length ω r  between two sides facing each other of the silica portion is smaller than a length Λ which is half of the pitch Γ; and   an air hole core or a core with multiple hexagonal air holes arranged in a triangular lattice configuration.   
   
   
       55 . A photonic band gap fiber with multiple air holes in silica portions extending in a longitudinal direction of the fiber, the fiber comprising:
 a cladding having an air hole periodic structure in an extended triangular lattice configuration with a length ω r  between two sides facing each other of the silica portions is smaller than a first pitch Λ, first rows of air holes, each first row comprising multiple hexagonal air holes at the first pitch Λ in a cross section of the fiber arranged through a silica partition wall, and second rows of air holes, each second row comprising multiple hexagonal air holes at a second pitch Γ which is twice the first pitch arranged through hexagonally-shaped silica portions; and   an air hole core or a core with multiple hexagonal air holes arranged in a triangular lattice configuration.   
   
   
       56 . The photonic band gap fiber according to  claim 55 , wherein a thickness ω b  of the silica partitioning wall is in a range of 0005Λ≦ω b ≦0.2Λ. 
   
   
       57 . The photonic band gap fiber according to  claim 55 , wherein a thickness ω b  of the silica partitioning wall is in a range of 0.05Λ≦ω b ≦0.5Λ. 
   
   
       58 . The photonic band gap fiber according to  claim 55 , wherein ω r , the length between two sides facing each other of the silica portions is in a range 0.4Λ≦ω r ≦Λ. 
   
   
       59 . The photonic band gap fiber according to  claim 54  or  55 , wherein a diameter D of the air hole core has a relationship of 0.7Λ≦D≦3.3Λ with respect to the first pitch Λ. 
   
   
       60 . The photonic band gap fiber according to  claim 54  or  55 , wherein a diameter D of the air hole core has a relationship of 4.7Λ≦D≦7.3Λ with respect to the first pitch Λ. 
   
   
       61 . The photonic band gap fiber according to  claim 54  or  55 , wherein a diameter D of the air hole core has a relationship of 8.7Λ≦D≦11.3Λ with respect to the first pitch Λ. 
   
   
       62 . The photonic band gap fiber according to  claim 54  or  55 , wherein three or more layers of the air hole periodic structure in the extended triangular lattice configuration in the cladding are provided outside the core. 
   
   
       63 . The photonic band gap fiber according to  claim 54  or  55 , having a core mode in which 60% or more of a transmitting power is concentrated in the air hole core region, and optical characteristics wherein a surface mode is substantially absent. 
   
   
       64 . The photonic band gap fiber according to  claim 54  or  55 , having an optical characteristic wherein only a single core mode (where the number of modes in case of all degraded modes is taken as 1) is present. 
   
   
       65 . The photonic band gap fiber according to  claim 54  or  55 , having an optical characteristic wherein a core mode is present within a range in which a wavelength λ, transmitted in the fiber, satisfies a range of 0.6≦Γ/λ≦1.7. 
   
   
       66 . The photonic band gap fiber according to  claim 54  or  55 , having an optical characteristic wherein a core mode is present within a range in which a wavelength λ, transmitted in the fiber, satisfies a range of 1.5≦Γ/λ≦2.4. 
   
   
       67 . The photonic band gap fiber according to  claim 54  or  55 , having an optical characteristic wherein a core mode is present when a wavelength λ, transmitted in the fiber, satisfies a range of 2.1≦Γ/λ≦3.5. 
   
   
       68 . The photonic band gap fiber according to  claim 54  or  55 , having an optical characteristic wherein a core mode is present when a wavelength λ, transmitted in the fiber, satisfies a range of 0.7≦Γ/λ≦2.4. 
   
   
       69 . A method of producing a photonic band gap fiber to obtain the photonic band gap fiber, the method comprising:
 arranging a silica capillary tubes and hollow silica tubes, having wall thicknesses greater than that of the capillary tubes, into first rows of air holes and second rows of air holes, wherein each first row comprises multiple capillary tubes and each second row comprises capillary tubes and hollow silica tubes alternately arranged and disposed such that a capillary arrangement of a cross section of the fiber forms an extended triangular lattice;   forming an air hole core region by
 eliminating a central hollow silica tubes or 
 eliminating the central hollow silica tube together with capillary tubes and hollow silica tubes surrounding the central silica tube, or 
 forming a capillary tube bundle in the capillary core region by replacing the central silica tube with capillary tubes; 
   forming a preform for fiber spinning by heating the arrangement of capillary tubes and hollow silica tubes and integrating the arrangement while maintaining a pressure in spaces in the capillary tubes at a high level and pressure in spaces within the hollow silica tubes at a low level, such that the spaces within the hollow capillary tubes collapse, and air holes in the capillary tubes are converted to hexagonal shapes; and   spinning the preform.   
   
   
       70 . The method of producing a photonic band gap fiber according to  claim 69 , wherein
 the capillary tubes have annular cross sections;   the hollow silica tubes have annular cross sections and thick walls having a thickness equal to a diameter of the capillary tubes.   
   
   
       71 . The method of producing a photonic band gap fiber according to  claim 69 , wherein forming the preform for fiber spinning comprises integrating the arrangement of capillary tubes and silica rods while it is inserted in a hole of a silica tube. 
   
   
       72 . The method of producing a photonic band gap fiber according to  claim 71 , wherein only the spaces in the capillary tubes in the arrangement inserted in the air hole of the silica tube is maintained at or above the atmospheric pressure, and the spaces other than the spaces in the capillary tubes, including the spaces in the hollow silica tubes, are maintained in a low pressure condition when performing the integration. 
   
   
       73 . The method of producing a photonic band gap fiber according to  claim 69 , wherein forming the air hole core region comprises eliminating the central hollow silica tube. 
   
   
       74 . The method of producing a photonic band gap fiber according to  claim 69 , wherein forming the air hole core region comprises eliminating the central hollow silica tube together with the capillary tubes and hollow silica tubes surrounding the central silica tube in no less than one layer and no more than five layers. 
   
   
       75 . The method of producing a photonic band gap fiber according to  claim 69 , wherein forming the air hole core region comprises replacing the central hollow silica tube with capillary tubes. 
   
   
       76 . The method of producing a photonic band gap fiber according to  claim 69 , wherein forming the air hole core comprises replacing the central hollow silica tube together with hollow silica tubes surrounding the central hollow silica tube with capillary tubes. 
   
   
       77 . The method of producing the photonic band gap fiber according to  claim 69 , wherein the arrangement of capillary tubes and hollow silica tubes is provided such that the air hole periodic structure in an extended triangular lattice configuration surrounding the core region has three or more layers of hollow silica tubes.