Problem on coupling of light

Question

If an LED is used to excite a single mode fiber, describe the coupling of light to the fiber? You can use equations, MATLAB, and so on. if required.

Answer 1

The number of modes supported by a single mode fiber is given by equation for a given wavelength is determined by:

The amount of light that an SM fiber can accept is determined by the acceptance angle of the fiber, which is by the numerical aperture (NA) of the fiber. The emission profile of an LED is Gaussian.

θ acceptance = Sin^-1(NA)

NA = √ (n_co² – n_cl²)

Only those rays, which lie within θ and 90 degrees, are coupled into the SM fiber.