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Wide band flat gain Raman amplifier for DWDM communication systems

Raman amplifier has been found to be an attractive candidate for optical dense wavelength division multiplexing (DWDM) system. This paper investigates Raman gain with forward pumping using only four pumping lasers for DWDM system. Considering the threshold power for various pumps, the composite working band and the Amplified Spontaneous Emission (ASE) noise are also estimated using the actual band model. Then, we investigate the use of coaxial fiber with single pump laser, which gives reasonably flat Raman gain spectrum. Then, we propose Raman amplifier with two pumps using coaxial fiber, showing that, such Raman amplifier can cover the C and L bands with low ripples. We conclude that, decreasing the number of pumps, also decreases the ASE.