Reduced coating diameter chlorine-doped silica optical fibers with low loss and microbend sensitivity

Abstract

The optical fiber disclosed has a glass fiber including a core and a cladding. The core comprises silica glass doped with chlorine and having an outer radius r1 between 3.0 microns and 10.0 microns. The cladding has an outer radius r4 not less than 50.0 microns. A primary coating surrounding the cladding has a thickness (r5−r4) between 5.0 microns and 20.0 microns, and an in situ modulus less than 0.30 MPa. A secondary coating surrounding the primary coating has a thickness (r6−r5) between 8.0 microns and 30.0 microns, a Young's modulus greater than 1500 MPa, and a normalized puncture load greater than 3.6×10−3 g/micron2. The optical fiber has a 22-meter cable cutoff wavelength less than 1530 nm, an attenuation at 1550 nm of less than 0.17 dB/km, and a bending loss at 1550 nm of less than 3.0 dB/turn.

What is claimed is: 
     
         1 . An optical fiber comprising:
 a glass fiber, the glass fiber including a core region and a cladding region surrounding and directly adjacent to the core region, the core region comprising silica glass doped with chlorine and having an outer radius r 1  in a range from 3.0 microns to 10.0 microns, the cladding region having an outer radius r 4  greater than or equal to 50.0 microns;   a primary coating with an outer radius r 5  surrounding and directly adjacent to the cladding region, the primary coating having a thickness (r 5 −r 4 ) in a range from 5.0 microns to 25.0 microns and an in situ modulus less than 0.30 MPa; and   a secondary coating with an outer radius r 6  less than or equal to 110 microns surrounding and directly adjacent to the primary coating, the secondary coating having a thickness (r 6 −r 5 ) in a range from 8.0 microns to 30.0 microns, a Young's modulus greater than 1500 MPa, and a normalized puncture load greater than 3.6×10 −3  g/micron 2 ;   wherein the optical fiber has a 22-meter cable cutoff wavelength less than 1530 nm, an attenuation at 1550 nm of less than 0.17 dB/km, and a bending loss at 1550 nm, determined from a mandrel wrap test using a mandrel with a diameter of 20 mm, of less than 3.0 dB/turn.   
     
     
         2 . The optical fiber of  claim 1 , wherein:
 the core region has a step index relative refractive index profile with a relative refractive index Δ 1  in a range from 0.08% to 0.30%.   
     
     
         3 . The optical fiber of  claim 1 , wherein:
 the core region has a graded index relative refractive index profile with a maximum relative refractive index Δ 1max  in a range from 0.08% to 0.50%.   
     
     
         4 . The optical fiber of  claim 1 , wherein the chlorine has a concentration in a range from 1.5 wt % to 7.0 wt %. 
     
     
         5 . The optical fiber of  claim 1 , wherein the cladding region comprises:
 an inner cladding region surrounding and directly adjacent to the core region, the inner cladding region having an outer radius r 2  and a thickness (r 2 −r 1 ) in a range from 1 micron to 7 microns; and   an outer cladding region surrounding and directly adjacent to the inner cladding region, the outer cladding region having an outer radius r 4  in a range from 50 microns to 70 microns;   wherein a relative refractive index Δ 2  of the inner cladding region is less than a relative refractive index Δ 4  of the outer cladding region.   
     
     
         6 . The optical fiber of  claim 5 , wherein:
 the relative refractive index Δ 2  is substantially zero; and   the relative refractive index Δ 4  is in a range from 0.05% to 0.30%.   
     
     
         7 . The optical fiber of  claim 5 , wherein:
 the relative refractive index Δ 2  is in a range from −0.25% to 0.0%; and   the relative refractive index Δ 4  is substantially zero.   
     
     
         8 . The optical fiber of  claim 5 , wherein:
 the relative refractive index Δ 2  is in a range from −0.25% to −0.0%; and   the relative refractive index Δ 4  is in a range from 0.05% to 0.30%.   
     
     
         9 . The optical fiber of  claim 1 , wherein the cladding comprises:
 an inner cladding region surrounding and directly adjacent to the core, the inner cladding region having a thickness (r 2 −r 1 ) in a range from 1 micron to 7 microns; and   a depressed index cladding region surrounding and directly adjacent to the inner cladding region, the depressed index cladding region having an outer radius r 3  in a range from 15 microns to 40 microns;   an outer cladding region surrounding and directly adjacent to the depressed index cladding region, the outer cladding region having an outer radius r 4  in a range from 50 microns to 70 microns;   wherein a relative refractive index Δ 3  of the depressed index cladding region is less than a relative refractive index Δ 2  of the inner cladding region and a relative refractive index Δ 4  of the outer cladding region.   
     
     
         10 . The optical fiber of  claim 9 , wherein the relative refractive index Δ 3  is in a range from −0.25% to 0.0%. 
     
     
         11 . The optical fiber of  claim 9 , wherein the relative refractive index Δ 2  region is less than the relative refractive index Δ 4 . 
     
     
         12 . The optical fiber of  claim 1 , wherein:
 the in situ modulus of the primary coating is less than or equal to 0.30 MPa;   the Young's modulus of the secondary coating is larger than or equal to 1600 MPa;   a diameter 2r 5  of the primary coating is less than or equal to 190 microns; and   a diameter 2r 6  of the secondary coating is less than or equal to 230 microns.   
     
     
         13 . The optical fiber of  claim 12 , wherein the diameter 2r 5  of the primary coating is less than or equal to 155 microns. 
     
     
         14 . The optical fiber of  claim 12 , wherein the thickness (r 5 −r 4 ) is in a range from 10.0 microns to 17.0 microns. 
     
     
         15 . The optical fiber of  claim 12 , wherein the diameter 2r 6  of the secondary coating is less than or equal to 190 microns. 
     
     
         16 . The optical fiber of  claim 12 , wherein the thickness (r 6 −r 5 ) is in a range from 8.0 microns to 20.0 microns. 
     
     
         17 . The optical fiber of  claim 1 , wherein the secondary coating has a normalized puncture load greater than 4.4×10 −3  g/micron 2 . 
     
     
         18 . The optical fiber of  claim 1 , wherein the primary coating is a cured product of a coating composition comprising:
 a radiation-curable monomer;   an adhesion promoter, the adhesion promoter comprising an alkoxysilane compound or a mercapto-functional silane compound; and   an oligomer, the oligomer comprising:
 a polyether urethane acrylate compound having the molecular formula: 
   
       
         
           
           
               
               
           
         
         
           
             wherein
 R 1 , R 2  and R 3  are independently selected from linear alkylene groups, branched alkylene groups, or cyclic alkylene groups; 
 y is 1, 2, 3, or 4, and 
 x is between 40 and 100; and 
 
           
           a di-adduct compound having the molecular formula: 
         
       
       
         
           
           
               
               
           
         
         
           
              wherein the di-adduct compound is present in an amount of at least 1.0 wt % in the oligomer. 
           
         
       
     
     
         19 . The optical fiber of  claim 18 , wherein the oligomer is the cured product of a reaction between:
 a diisocyanate compound;   a hydroxy (meth)acrylate compound; and   a polyol compound, said polyol compound having unsaturation less than 0.1 meq/g;   wherein said diisocyanate compound, said hydroxy (meth)acrylate compound and said polyol compound are reacted in molar ratios n:m:p, respectively, wherein n is in the range from 3.0 to 5.0, m is within ±15% of 2n-4, and p is 2.   
     
     
         20 . The optical fiber of  claim 1 , wherein the secondary coating is the cured product of a composition comprising:
 a first monomer, the first monomer comprising a first bisphenol A diacrylate compound.   
     
     
         21 . The optical fiber of  claim 20 , wherein the coating composition further comprises a second monomer, the second monomer comprising a second bisphenol A diacrylate compound. 
     
     
         22 . The optical fiber of  claim 1 , wherein the secondary coating is the cured product of a composition comprising:
 an alkoxylated bisphenol-A diacrylate monomer in an amount greater than 55 wt %, the alkoxylated bisphenol-A diacrylate monomer having a degree of alkoxylation in the range from 2 to 16; and   a triacrylate monomer in an amount in the range from 2.0 wt % to 25 wt %, the triacrylate monomer comprising an alkoxylated trimethylolpropane triacrylate monomer having a degree of alkoxylation in the range from 2 to 16 or a tris[(acryloyloxy)alkyl] isocyanurate monomer.