The Numerical Aperture is given by,

NA  =  Sin θ_a

Where θ_a is the Acceptance angle

The bend of a fiber causes loss in emittance and increase in attenuation as the angle of incidence decreases at the points where curveted radius is too small and the condition of total internal reflection is not fulfilled. In this experiment an apparatus of varying radii is used to study the bending losses involved. When a fiber is bend specified number of turns on various diameters, loss occurs in accordance with the diameter and it can be seen that, the loss will increase with respect to the decrease in diameter.

Splice loss is caused by a number of factors. Loss is minimized when the two fiber cores are identical and perfectly aligned, splices are properly finished and no dirt is present. Only the light that is coupled into the receiving fiber's core will propagate, so all the rest of the light becomes splice loss

The Numerical Aperture is given by,

NA  =  Sin θ_a

Where θ_a is the Acceptance angle

In an optical fiber, the normalized frequency, the V number is given by

V  =  (  2πa  /  λ  )  √  (  n₁  -  n₂  )

V  =  (  2πa  /  λ  )  NA

Where a is the core radius, λ is the wavelength in vacuum, n₁ is the maximum refractive index of the core, n₂ is the refractive index of the homogeneous cladding, and applying the usual definition of the numerical aperture NA.

For a Gaussian power distribution (lasers used in communications have Gaussian power distribution) in a single mode optical fiber, the mode field diameter (MFD) is defined as the point at which the electric and magnetic field strengths are reduced to 1   /   e² of their maximum values, i.e., the diameter at which power is reduced to 1   /   e²   (0.135) of the peak power (because the power is proportional to the square of the field strength). For single mode fibers, the peak power is at the center of the core.

According to Snell’s law,

V  =  sin i  /  sin r

Where, n is the refractive index of transparent medium, i is the angle at which light enters the medium and r is the angle at which it gets refracted.