High gain Raman amplifier with inherent gain flattening and dispersion compensation

We report here an inherently gain-flattened, high-gain discrete Raman fiber amplifier design with 21 dB net gain (±1.4 dB gain ripple) over 25 nm bandwidth. The amplifier design is based on a W-shape highly nonlinear fiber, in which, optimized spectral variation of leakage loss has been used to achieve inherent gain flattening of Raman gain. The proposed fiber has an additional advantage of having a high negative dispersion coefficient (∼−84 ps/km nm) over the operating range of wavelength and thus the designed discrete amplifier module, based on this fiber, is also capable of compensating dispersion accumulated in one span (70 km) of transmission through G.652 fiber. Hence, the designed module is proposed as a composite amplifier and dispersion-compensating unit for 25 nm bandwidth, which is capable of handling both attenuation and dispersion of one span of G. 652 transmission.