Composite broad-band fiber Raman amplifiers using incoherent pumping.

This report presents an investigation of composite fiber Raman amplifiers (i.e., a distributed fiber Raman amplifier followed by a discrete fiber Raman amplifier) with in-coherent pumping, compared to conventional coherent pumping. It is shown that a flatter gain, noise figure and optical signal-to-noise ratio (OSNR) over 100-nm bandwidth can be achieved simultaneously by using two counter-incoherent pumps, compared to using six counter-coherent pumps. Moreover, it is found that a further improvement in gain, noise figure and OSNR flatness can be obtained in composite fiber Raman amplifiers with bi-directional incoherent pumping. The flatness of both gain and OSNR with a ripple of 1 dB is predicted by using one co-incoherent pump and one counter-incoherent pump.