Patent ID: 7813611

Claim:
An optical fiber comprising: (i) a circular core comprising Al doped silica having a first index of refraction n 1 , but no Er or Yb; (ii) at least one silica based cladding surrounding the core and having a second index of refraction n 2 , such that n 1 >n 2 ; (iii) a hermetic carbon based coating surrounding said cladding, said hermetic coating being 300 nm to 1000 nm thick; and (iv) a second coating surrounding said hermetic coating, said second coating being 5 μm to 80 μm thick, wherein when said fiber is treated at 150° C. in 100% 1 atm H 2 for 170 hours, the attenuation change in 950 nm to 1150 nm wavelength band is less than 1.5 dB/km.