Highspeed communications and computations are the main industrial and academicdemands. Optical method is one of interesting alternatives for doing this purpose1.
FiberOptic communication offers higher frequency transmission of signals withgreater bit rate and larger data carrying capacity over a long distance. Thismeans of data transmission is with a lower loss and interference if compared tothe normal copper wire used in the electrical telecommunication systems. Opticalfiber is widely used in the application of internet communication technology indeveloping countries largely due to its feasibility to transmit data over a longerdistance2.In spite of all these benefits; optical fiber is not an ideal medium. Thequality of the optical pulse is degraded the system performances significantly due to various effects whichmainly include fiber loss, group velocity dispersion (GVD) and self-phasemodulation (SPM) 3.
Basically, the linear effects (including the loss, GVD)are responsible for changes in pulse shape while nonlinear effects (such asSPM) are responsible for changes of pulse spectrum. The combination oflinear andnonlineareffectsleads to both the temporal and spectral changes of the pulse 4-5. The pulse degradation in the fiber limits themaximum transmission distance and the transmission rate of the fiber link;hence it is very important to analyze the pulse evolution behavior of thepropagating pulse in the fiber 3. The pulse propagation is modeled usingnonlinear Schrodinger equation (NLSE) 2. The chirpparameter have important role in pulse propagation.When C> 0 is referred to as up-chirp/positive chirp where the instantaneousfrequency increases linearly from the leading to the trailing edge On the otherhand, the frequency decreases linearly from the leading to the trailing edgeC< 0 and the same is termed as down-chirp/negative chirp 6.In anomalous dispersion regime ( ), thecompression occurs for the up-chirped pulses, whereas the broadening takesplace for the down-chirped pulses. The opposite situation happens for up- anddown-chirped pulses propagating in the normal dispersion regime ) 4.
In this research work is to investigate graphically the effect of Chirping with GVD, effect of SPM and thecomparison of GVD alone andcombining SPM with GVD in anomalous dispersion regime. The input pulsedistribution is taken as a Gaussian pulse. In general, the non-linearSchrodinger Equation (NLSE) has been carried out by using a Split-step Fourier method(SSFM) for solving linear& non-linear effects.
Weimplement code in MATLAB based on SSFM for Comparison of Gaussian opticalpulses for different values of chirp parameter for anomalous dispersion and normal dispersion regime, how theChirp parameter influences pulse broadening, Nonlinear effect (SPM) ondifferent propagation distance where the extra frequencies generated through SPM broaden thefrequency spectrum of the pulse result in SPM induced symmetrical spectral broadening 7. And finally the comparison of pulse evolution withGVD alone and combining SPM with GVD in anomalous and normal dispersion regimehas been analyzed.