In this paper to enhancement the Raman gain, two Raman Amplifiers (RAs) are used one is forward pump Raman amplifier and the second is feedback pump Raman amplifier in cascaded form. The performance of the system is analyzed in terms of fiber type, fiber length, pump power and gain coefficient for enhancement the gain of fiber Raman amplifier. We present the performances and characteristics of RAs by utilizing a set of coupled differential equations and numerical simulations. Three types of fibers with different gain characteristics are used in our numerical simulations. So, the optimum initial values of the pump powers for a system with three pumps are recalculated and optimized again.

Efficient transmission of data within optical fiber cables within radiation environments is a challenge. It leads to severe attenuations in the optical fiber cables. This issue is addressed in this manuscript. Experimental measurements are conducted in order to overcome the radiation influence on single mode optical fiber cables. Two experiments are implemented. The first one depends on 5 m single mode patch cords fiber cable. This cable is subjected to gamma radiation at different radiation doses of 5 kGy, 10 kGy, 15 kGy and 20 kGy with dose rate of 1.296 KGy/ hr. These doses are the maximum doses that the cable of fiber is exposed in normal conditions in our radiation environment. The second experiment uses 3 m single mode fiber cable with different jackets. In this experiment, the cable is degraded by gamma radiation of doses 5 kGy, 10 kGy, 15 kGy and 25 kGy and dose rate of 2.273 KGy/hr. The fiber cables are degraded through gamma 1 radiation facility within Egypt Mega gamma1 in National Center for Radiation Research and Technology of Egyptian Atomic Energy Authority (EAEA). Then, the attenuation of these cables is measured in two different places in National Institute for Laser Science in Cairo University and Africa Teleco private company. The measurements are done using laser sources at spectral wavelengths of 1310 nm and 1550 nm. Hence, various readings of attenuations in dB are demonstrated. Attenuation recovery is of primary concern. It is executed within 36 days. The experimental results confirm the superiority of operation at 1550 nm over that of 1310 nm. The experimental measurements are performed before and after radiation degradation for comparison purposes. The recovered attenuation achieves better results comparable to results before degradations.

The Raman gain coefficient, the attenuations at signal and pump wavelengths and the refractive indices of both core and cladding of silica doped Germania optical fiber are functions of the Germania ratio, temperature and wavelengths. The Raman amplifier gain increases with Germania ratio but it decreases with temperature. Also, Raman gain either increases or decreases with signal wavelength. As the fiber core radius increases, the Raman gain decreases. The gain distribution through the amplifier length of dual pumps with power divided ratio (S=0.5) is better than that for the forward pump amplifier and the backward pump amplifier. The forward pump has a maximized gain but the backward pump has a minimized gain, while the dual pumps have both the maximum and minimized gains. The final amplifier gain for the three kinds of pumps with the same pump power (Pp) is equally.The pump wavelength (λp=1.4553μm) gives the biggest Raman gain at the center of wideband signal wavelength (λs=1.50 to 1.60μm). With λp =1.48μm, the gain increases with λs until λs=1.57μm and after that the gain decreases with λs and so with the above three kinds of pumps, gain fluctuations over the band wavelength of signal. The threshold pump power and gain saturation are studied.

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