so the above equation can be simplified to

For a homogeneous medium is not a function of space. Eqn (1) then gives .

Substituting in above eqn.

we get

(5)

This equation is called the Wave Equation .

If we do the similar analysis for the magnetic field we get the same wave equation for the magnetic field

(6)

To analyse the propagation of light inside an optical fiber, we have to solve the wave equation with appropriate boundary conditions.

Since we have chosen the cylindrical coordinate system , we