Raman amplification in multimode fiber

We demonstrate that the Raman gain of the fundamental mode in graded-index multimode fiber (MMF) is comparable to that of standard single-mode fiber using the same pump power. Moreover, we show that mode-selective gain is significantly enhanced by the radial dependence of the GeO2 concentration in these fibers. The mode-selective gain is also shown, via impulse responses and eye diagrams, to reduce the intersymbol interference for near center-launch excitations and thereby enhance high-speed MMF link performance.