That is a nice link.
Ironically, I just had fiber optic Internet installed and asked the installer some related questions.* The fiber that was used had a "goo" around it, which was removed prior to fusing. The installer mentioned that the cable is also available without the goo.
If the goo was silicone oil (RI = 1.4), then the N.A. would be expected to be <1. But what if the fiber did not have the goo? Then I presume air (RI =1) would be the interface, which would lead to a N.A. of >1.
So, I think to answer Kavitha's question with certainty, one would need to know the construction of the cable.
John
*My question was related to the effects of stress on the glass fiber. The effect of stress on glass is easily visible using a set of polarizing filters. The installer threw out the term, "microkinks," which may be related to that. I have not read much on this, I was just curious based on my prior experience with optics and glass blowing.