Bend Resistant Multimode Optical Fiber

Abstract

Bend resistant multimode optical fibers are disclosed herein. Multimode optical fibers disclosed herein comprise a core region and a cladding region surrounding and directly adjacent to the core region, the cladding region comprising a depressed-index annular portion comprising a depressed relative refractive index which is spaced from the core at least 0.5 microns and less than 4 microns.

1 . A multimode optical fiber comprising:
 a graded index glass core; and   an inner cladding surrounding and in contact with the core, and a second cladding comprising a depressed-index annular portion surrounding the inner cladding, said depressed-index annular portion having a refractive index delta less than about −0.2% and a width of at least 1 micron, wherein the width of said inner cladding is at least 0.5 microns and less than 4 microns.   
   
   
       2 . The optical fiber of  claim 1 , wherein said inner cladding has a refractive index delta greater than −0.05% and less than 0.05% and comprises an inner radius of about 25 microns and the width of said inner cladding is at least 1 micron. 
   
   
       3 . The optical fiber of  claim 1 , wherein the width of said inner cladding is less than 3 microns. 
   
   
       4 . The fiber of  claim 1 , wherein said fiber further exhibits a 1 turn 30 mm diameter mandrel wrap attenuation increase of less than or equal to 0.1 dB/turn at 850 nm. 
   
   
       5 . The fiber of  claim 1 , wherein said fiber further exhibits a 1 turn 20 mm diameter mandrel wrap attenuation increase, of less than or equal to 0.1 dB/turn at 850 nm. 
   
   
       6 . The fiber of  claim 1 , wherein said fiber further exhibits a 1 turn 10 mm diameter mandrel wrap attenuation increase, of less than or equal to 0.5 dB/turn at 850 nm. 
   
   
       7 . The fiber of  claim 2 , wherein said depressed-index annular portion has a width greater than 2 microns. 
   
   
       8 . The fiber of  claim 7 , wherein said depressed-index annular portion has a width less than 10 microns. 
   
   
       9 . The fiber of  claim 1 , wherein said fiber further exhibits an overfilled bandwidth greater than 1.5 GHz-km at 850 nm. 
   
   
       10 . The fiber of  claim 1 , wherein said fiber further exhibits an overfilled bandwidth greater than 2.0 GHz-km at 850 nm. 
   
   
       11 . The fiber of  claim 1 , wherein said fiber further exhibits an overfilled bandwidth greater than 4.0 GHz-km at 850 nm. 
   
   
       12 . The fiber of  claim 1 , wherein said fiber further exhibits an overfilled bandwidth greater than 500 MHz-km at 1300 nm. 
   
   
       13 . The fiber of  claim 1 , wherein said depressed-index annular portion exhibits a refractive index delta less than −0.3 percent. 
   
   
       14 . The fiber of  claim 1 , wherein said depressed-index annular portion exhibits a refractive index delta less than −0.4 percent. 
   
   
       15 . The fiber of  claim 1 , wherein said depressed-index annular portion comprises fluorine doped silica. 
   
   
       16 . The fiber of  claim 1 , wherein said depressed-index annular portion comprises a plurality of non-periodically disposed voids. 
   
   
       17 . The fiber of  claim 1  wherein the maximum refractive index delta of the graded index glass core is greater than 0.5% and less than 1.2%. 
   
   
       18 . The fiber of  claim 1  wherein the 1 turn 10 mm diameter attenuation increase is less than 0.6 dB for all wavelengths between 800 and 1400 nm. 
   
   
       19 . A multimode optical fiber comprising:
 a graded index glass core; and   an inner cladding surrounding and in contact with the core, and a second cladding comprising a depressed-index annular portion surrounding the inner cladding, said depressed-index annular portion having a refractive index delta less than about −0.2% and a width of at least 1 micron, wherein the width of said inner cladding is at least 0.5 microns and said fiber further exhibits a 1 turn 10 mm diameter mandrel wrap attenuation increase, of less than or equal to 0.4 dB/turn at 850 nm, and an overfilled bandwidth greater than 1.5 GHz-km at 850 nm.   
   
   
       20 . The multimode fiber of  claim 19  further comprising a numerical aperture of greater than 0.18. 
   
   
       21 . The multimode fiber of  claim 19 , wherein said depressed-index annular portion comprises fluorine. 
   
   
       22 . The multimode fiber of  claim 19 , wherein said fiber further exhibits an overfilled bandwidth greater than 2.0 GHz-km at 850 nm. 
   
   
       23 . The multimode fiber of  claim 1  further comprising a numerical aperture of greater than 0.14.