Optical fiber cables for microduct installations

Abstract

The specification describes optical fiber cables designed for microduct installations. The microduct cables are coated with a sheath having particulates added to modify the drag of the outer surface of the cable to air, and thereby facilitate air blown installation. The particulates are nanoclay, silica, alumina, or other suitable solid particles of less than 5 microns. The coating comprises a prepolymer containing the filler, and is UV cured.

1 . A method for the manufacture of microduct cable comprising: 
 (a) assembling together a plurality of optical fibers to form an optical fiber bundle, the optical fibers having a polymer coating,    (b) coating the bundle with a coating fluid, and    (c) exposing the coated bundle to light radiation to cure the coating fluid, the invention characterized in that the coating fluid comprises: 
 (i) a prepolymer, and  
 (ii) 1-20% of a solid particle filler, wherein the average particle size of the particles in the solid particle filler is less than 5 microns.  
   
     
     
         2 . The method of  claim 1  wherein the solid particle filler comprises particles selected from the group consisting of nanoclay, alumina and silica.  
     
     
         3 . The method of  claim 2  wherein the particles are clay platelets having an aspect ratio in the range  15 - 2000  and a maximum average length of less than 1000 nm.  
     
     
         4 . The method of  claim 1  wherein the bundle comprises a group of separate optical fibers.  
     
     
         5 . The method of  claim 1  wherein the bundle comprises optical fiber ribbons.  
     
     
         6 . The method of  claim 3  wherein the clay platelets comprise a mixture of silicates selected from the group consisting of aluminum, magnesium and mixtures thereof.  
     
     
         7 . The method of  claim 6  wherein the clay platelets have a thickness of less than 15 nm.  
     
     
         8 . The method of  claim 6  wherein the clay platelets comprise one or more materials selected from the group consisting of montmorillonite, hectorite, bentonite, and synthetic clay.  
     
     
         9 . The method of  claim 1  wherein the prepolymer comprises a UV curable acrylate.  
     
     
         10 . A microduct cable comprising a bundle of optical fibers, the optical fibers having a polymer coating, and a polymer sheath covering the bundle, the polymer sheath having a surface comprising a UV cured polymer with 1-20% filler, the filler consisting of particles selected from the group consisting of nanoclay, alumina and silica with an average particle size of less than 2 microns.  
     
     
         11 . A microduct cable comprising: 
 (a) a bundle of optical fibers,    (b) a coating covering the bundle, the coating comprising: 
 i. a polymer,  
 ii. a photoinitiator,  
 iii. 1-20% of a filler, the filler consisting of clay platelets having an aspect ratio in the range  15 - 2000  and a maximum average length of less than 1000 nm.  
   
     
     
         12 . The microduct cable of  claim 11  wherein the coating comprises an inner layer without filler and an outer layer with filler.  
     
     
         13 . The microduct cable of  claim 11  wherein the coating has a surface comprising portions without filler and portions with filler.  
     
     
         14 . The microduct cable of  claim 13  wherein the portions with filler are stripes.  
     
     
         15 . An optical fiber installation comprising: 
 (1) a plurality of microducts,    (2) a coating covering the plurality of microducts,    (3) a microduct cable in one of the microducts, the microduct cable comprising: 
 (a) a bundle of optical fibers,  
 (b) a coating covering the bundle, the coating comprising: 
 i. a polymer,  
 ii. a photoinitiator,  
 iii. 1-20% of a filler, the filler consisting of clay platelets having an aspect ratio in the range  15 - 2000  and a maximum average length of less than 1000 nm.  
 
   
     
     
         16 . The optical fiber of  claim 15  wherein the clay platelets comprise a mixture of silicates selected from the group consisting of aluminum, magnesium and mixtures thereof.  
     
     
         17 . The optical fiber installation of  claim 16  wherein the clay platelets have a thickness of less than 15 nm.  
     
     
         18 . The optical fiber installation of  claim 17  wherein the clay platelets comprise one or more materials selected from the group consisting of montmorillonite, hectorite, bentonite, and synthetic clay.  
     
     
         19 . A method for installing a microduct cable in a microduct comprising the step of air blowing the microduct cable through the microduct, the invention characterized in that the microduct cable has a surface coating comprising: 
 (a) a polymer,    (b) a photoinitiator,    (c) 1-20% of a filler, the filler consisting of clay platelets having an aspect ratio in the range  15 - 2000  and a maximum average length of less than 1000 nm.