[Solved] A silica optical fiber with a core diameter large enough to be considered by ray theory analysis has a core ...

Question:

A silica optical fiber with a core diameter large enough to be considered by ray theory analysis has a core refractive index of 1.50 and a cladding refractive index of 1.47.

Determine: (a) the critical angle at the core–cladding interface; (b) the NA for the fiber; (c) the acceptance angle in air for the fiber.

Solution/Given:

Here are the given from the question.

Core refractive index (n1) = 1.50

Cladding refractive index (n2) = 1.47

Critical angle at the core–cladding interface φc = ?

Numerical aperture (NA for the fiber) = ?

Acceptance angle in air for the fiber (θa) = ?

(a) To find the critical angle φc from the core and cladding refractive index,

φc = sin−1(n2/n1) = sin−1(1.47/1.5) = 78.5°

(b) The NA can be found by using the equation, NA = (n12 - n22)0.5

= (1.52 - 1.472)0.5

= (2.25 − 2.16)0.5 = 0.3

(c) The acceptance angle in air θa

= θa = sin−1(NA) = sin−1(0.30)

= 17.4°