Question

You are provided with two materials, A (Refractive index: 1.448) and B (Refractive index: 1.447). Choose core and cladding material of the fiber from above where Total internal reflection could be achieved successfully. Find critical angle, Numerical aperture, acceptance angle for the fiber you chosen. The wavelength of the light you can use is 1550 nm. And how many number of modes will propagate through your fiber (if d=9 micron and d=50 micron)?

Answer 1

Given:

You are provided with two materials, A (Refractive index: 1.448) and B (Refractive index: 1.447).

The wavelength of the light you can use is 1550 nm.

To find:

Choose core and cladding material of the fiber from above where Total internal reflection could be achieved successfully.

Find critical angle, Numerical aperture, acceptance angle for the fiber you chosen.  

And how many number of modes will propagate through your fiber (if d=9 micron and d=50 micron)?

Solution:

From given, we have,

The index of refraction of the inner core is n1 = 1.448.

The index of refraction of the outer cladding is n2 = 1.447.

Critical angle = ∅c = n2/n1 = 1.447/1.448 = 0.999

Numerical aperture = NA = √ (n1^2 - n2^2) = √ (1.448^2 - 1.447^2) = 0.0538

Acceptance angle = ∅max = sin^-1 √ (n1^2 - n2^2) = sin^-1 (0.0538) = 3.084

V number = 2π/λ a NA = 2π/λ a √ (n1^2 - n2^2)

upon substituting the values, we get,

V = 8.94.