EFFECT OF LOSS AND PULSE WIDTH VARIATION ON SOLITON PROPAGATION Part I. Fundamentals of soliton propagation

In this work, the propagation of solitons in single-mode optical fibers has been investigated theoretically by using the nonlinear Schrödinger equation. This equation combines the effects of group velocity dispersion and self-phase modulation present in optical fibers and also takes into account the loss of optical fiber. The nonlinear Schrödinger equation has been solved numerically by using the split-step Fourier transform technique. In particular, soliton solutions of this equation are obtained. Computer simulations depicting the propagation of solitons having picosecond pulse widths, over several tens of kilometers in optical fibers with losses are presented. The results obtained for solitons in the lossless case demonstrate the shapepreserving property of the first order soliton and periodicity, splitting and compression properties of higher order solitons. Computer simulations show that the optical loss broadens the pulse width of solitons and increases the soliton period. However, this broadening in the pulse width is directly proportional to the optical loss unlike broadening effect of dispersion. It has found that the use of solitons in optical communication systems can improve the bit-rate over the same distance of propagation compared to normal optical communication systems even if no precaution is taken against the pulse broadening effect due to loss.