Raman effects in a highly nonlinear holey fiber: Amplification and modulation

We experimentally demonstrate that a short length of highly nonlinear holey fiber (HF) can be used for strong L⁺-band (1610-1640-nm) Raman amplification and ultrafast signal modulation. We use a pure silica HF with an effective area of just 2.85 μm² at 1550 nm, which yields an effective nonlinearity ∼15 times higher than in conventional silica dispersion-shifted fiber. Using a 75-m length of this fiber, we obtained internal Ramau gains of more than 42 dB and a noise figure of ∼6 dB under a forward single-pump scheme, and the Raman gain coefficient was experimentally estimated to be 7.6 × 10^-14 m/W. Also, an 11-dB signal extinction ratio in a Raman-induced all-optical modulation experiment was achieved with the same fiber.