Amplified spontaneous emission measurements and noise figure of the distributed fiber Raman amplifiers with terahertz bandwidth

Noise parameters of fiber Raman amplifiers with teraherz gain bandwidth are appeared in practice essentially better top theoretical limits and the amplifier noise performance is the subject of intensive investigations now. The experimental results on the amplified spontaneous emission (ASE) observation in the single mode fiber span using the backward pumped distributed FRA are presented in the report. Our measurements and quantity analysis show that physical principles of formation of the FRA optical noise with the counter pumping lead to very small gain coefficients and it almost correspond to spontaneous Raman properties in the silica fibers. Raman gain nonlinearity is the reason to reduce the real FRA noise figure much below the established 3 dB limit. Our analysis of experimental data on ASE measurements in silica fibers allows us to get the information about the nature of formation mechanism of the noise parameters in the practical FRA.