# Nonlinear Pulse Propagation in Optical Fibers

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#### nlse_solver.m

Simulation of Nonlinear Schrodinger Equation (NLSE) using the split-step Fourier scheme (SSFS). In SSFS, first NLSE is solved by ignoring nonlinearity over a small fiber section. The linear part is solved using a pair of FFTs. Next, the NLSE is solved by ignoring the linear part. This split-step approach is carried out iteratively.

This Module calls the following Sub Module / Component:

(1) fiber_prop.m
Which is a submodule to solve NLSE.
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Explore Further this Module:

10.1 Set the dispersion coefficient,  to zero and loss coefficient,  to zero. Launch a Gaussian pulse to the fiber. Compare the spectral width before and after propagation. Does the spectrum broaden? Explain. Does the pulse width (in time domain) change after the propagation? Calculate the rms spectral width and plot it as a function of fiber length.

10.2 Set the fiber length to 80 km. Change  from 0 to 14 ps.ps/km with a step of 2 ps.ps/km. Adjust the computational window (tmin and tmax) if necessary. Observe that the spectral broadening is reduced as the dispersion increases. Plot the rms spectral width vs dispersion coefficient . Does the pulse width change as  changes?

10.3 Set the dispersion coefficient,  to -5 ps.ps/km, loss coefficient,  to zero and fiber length to 80 km. Launch a secant-hyperbolic pulse to the fiber with the appropriate power so that the soliton is excited. Compare the pulse width before and after propagation. Compare the spectral width before and after propagation. Plot the soliton phase as a function of distance.

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