Noise Figure Analysis Of Distributed Fibre Raman Amplifier

Fibre Raman amplifiers are being deployed in many new long-haul and ultra long-haul fibre-optic transmission systems, making them the first and most widely commercialized nonlinear optical devices in telecommunications. One of the main reasons for this is their improved noise figure and reduced nonlinear penalty of fibre systems hence allowing for longer amplifier spans. In this paper, we have critically analyzed by simulation the noise figure of Distributed fibre Raman amplifiers for different pumping schemes. The main sources of optical noise and their effects on the noise figure and optical signal to noise ratio are also discussed. Our results show that the optical signal to noise ratio (OSNR) is higher for forward pumping than in backward pumping, while the noise figure (NF) was higher for backward pumping than in forward pumping. Both the NF and OSNR remains almost the same for shorter fibre length (< 10 Km), but change differently at longer fibre lengths and pump powers, depending on the pump configuration used. It was also found that OSNR increased as pump power increase beyond 100mW as the NF reduced for the two pump configuration. Results from our study are important in the design optimization of fibre Raman amplifiers in long haul signal transmissions.