الفهرس | Only 14 pages are availabe for public view |
Abstract The present work deals with the improvement of the performance of optical fiber amplifiers, which are major components in optical communication systems by studying, the characteristics of Raman amplifier and the characteristics of Erbium-Doped Fiber Amplifiers EDFA/Raman hybrid amplifier and comparing their performance. The main interest of the study is devoted to fiber amplifiers like Raman amplifiers and erbium doped fiber amplifier hybrid with Raman amplifier. The main idea is to study and improve the gain and noise of the amplifier through parameters which control it like input signal power, Raman pump power, Raman amplifier length in Raman amplifier and EDFA pump power and EDFA length with the last parameters in EDFA/Raman hybrid amplifiers. The thesis provides a numerical investigation of the performance of Raman amplifier and EDFA/Raman hybrid amplifiers. The performance parameters that have been investigated and compared are gain spectrum, optical noise figure, optical signal to noise ratio (OSNR). OSNR depends on the pump power of both types of amplifier, signal power and fiber length of both types. EDFA can be forward pumped and Raman amplifier can be reverse pumped. The parameters are calculated for different values for the pump power, fiber length and signal wavelengths and input signal power. The gain using these amplifiers covers the range 1.45-1.65 μm which is S, L and C bands. from the obtained results, It is found that, the performance of nonlinear optical amplifiers depends strongly on both the signal and pump wavelengths and the host material through the values of the emission and absorption cross sections. It is found also that, the gain in the case of EDFA/Raman Hybrid Optical Amplifier (HOA) is large for the signal wavelength 1.53 μm rather than Raman amplifier or EDFA. For the gain and noise figure, we found that both depend on the signal wavelength and input signal power as well as the pump power and the fiber length. It is found that, the optimum values of the parameters, which give higher gain and lower noise figure for EDFA/Raman HOA, are EDFA length of 15 m with Raman amplifier length 25 km at input signal power, -30 dBm for EDFA and Raman pump power of 100 mW. The broadening in the gain curve is 0.041 μm. Optical amplifiers could be pumped using either forward pumping schemes in erbium and backward pumping in Raman. We found that, for low pumping power levels, even though both forward and backward pumping methods provide the same gain. The forward pumping is better as its equivalent input noise figure is lower for erbium and the backward is better for Raman in the EDFA/Raman HOA. The higher gain obtained was 41.1 dB for EDFA/Raman hybrid amplifier at -30 dBm input signal power, 100 mW of both EDFA and Raman pump power and signal wavelength of 1.53 μm and the lower noise figure was 3.8 dB for EDFA only at -30 dBm input signal power, 100 mW of EDFA pump power at signal wavelength of 1.53 μm. |