Question

1. Which fibre has low numerical aperture?
(A) Step index
(B) Graded index
(C) Both (a) and (B)
(D) none of these​

Answer 1

Answer:

Numerical Aperture (NA)

Figure 5: Numerical Aperture. The Numerical Aperture (NA) of a fiber is defined as the sine of the largest angle an incident ray can have for total internal reflectance in the core. Rays launched outside the angle specified by a fiber's NA will excite radiation modes of the fiber.