Palagarla, Baji Babu (2017) Analysis of Nonlinear Pulse Propagation and Wave-mixing Characteristics in Semiconductor Optical Amplifier. Research Masters thesis, University of Southern Queensland. (Unpublished)
Abstract
This project is primarily focusses on nonlinear pulse propagation and four-wave mixing characteristics on semiconductor optical amplifiers (SOA). Since the project is on SOA, modified nonlinear Schrödinger equation (MNLSE) is used for theoretical modelling of SOA. The theoretical model includes SOA all nonlinear effects, gain dynamics, geometrical parameters, etc. Finite-difference beam propagation method is used to solve MNLSE and based on that MATLAB code is used to obtain nonlinear pulse propagation and wave mixing characteristics of SOA. In this project, initially, nonlinear single propagation in semiconductor optical amplifier (SOA) characteristics are obtained by propagating a single pulse in SOA.
In high-speed optical communication, different types of pulse shapes are used such as Gaussian pulse shape, Lorentzian pulse shape, and Secant-hyperbolic pulse shape, etc. Here, Gaussian, Lorentzian and Secant hyperbolic pulse shapes are taken as input of SOA (separately) for obtaining simulations of nonlinear pulse propagation characteristics. SOA output characteristics are obtained by varying input pulse energy and full-width at half-maximum (FWHM) or width of input pulse. In addition, pulse propagation characteristics are obtained by varying the length of SOA. By analyzing output pulse shapes for different energies, the peak positions of pulse shapes are shifted due to gain saturation effect. Self-phase modulation (SPM) and gain saturation effects contributes distortions in the output spectrum. It is also observed output FWHM of pulse shape has been increased by increasing the FWHM of input pulse shape, and length of SOA shows significant effect on output signal power.
Four-wave mixing (FWM) is a nonlinear technique to change wavelength of input pulse by using an additional input pulse shape. In this project, basic four wave mixing characteristics are obtained by using two homogeneous input pulse shapes using Gaussian, Lorentzian, Secant hyperbolic pulse shapes. The output characteristics are obtained based on varying input pulses energies, detuning of pulse input pulse shapes. Finally, the FWM output characteristics are obtained by varying the length SOA. Based on analysis of results, output energy of newly generated converted signal (or FWM signal) is dependent on both input pump and probe energies. The output results with respect to detuning of two input signals indicating that FWM conversion efficiency is falls with great extent after 1 THz for both positive and negative detuning. If detuning frequency is below 1 THz, conversion efficiency of pulse shapes is good for all combinations of input pulse shapes. Finally, it is observed that FWM signals power is highly dependent on length of SOA.
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| Item Type: | Thesis (Non-Research) (Research Masters) |
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| Item Status: | Live Archive |
| Faculty/School / Institute/Centre: | No Faculty |
| Supervisors: | Das, Narottam |
| Qualification: | Master of Engineering Science (Applied Telecommunications) |
| Date Deposited: | 19 Mar 2026 03:05 |
| Last Modified: | 19 Mar 2026 03:05 |
| Uncontrolled Keywords: | nonlinear pulse propagation; semiconductor optical amplifiers (SOA) |
| URI: | https://sear.unisq.edu.au/id/eprint/53183 |
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