OPTICAL FIBER AND METHOD FOR MAKING SUCH FIBER

摘要

According to one example of the invention an optical fiber comprises: (i) silica based, rare earth doped core having a first index of refraction n1; (ii) at least one silica based cladding surrounding the core and having a second index of refraction n2, such that n1> n2 with the following features, alone or in combination: said cladding includes 0.5 to 5 wt% F and 0.5 to 20 wt% B, said optical fiber has less than 8dB/km core background loss at a wavelength of 1280 nm. at least one of the core or cladding is doped with AI203 concentration is less than 2:1.