Design and Analysis of Gain-Flattened Raman Amplifiers with Novel Highly Nonlinear Photonic Crystal Fibers

In order to get a flat gain among the dense wavelength division multiplexing (DWDM) channels, design and numerical analysis of Raman fiber amplifier (RFA) based on photonic crystal fibers (PCFs) have been done. Simple pure silica square PCFs with 5 rings air-hole and hexagonal PCFs with 8 rings air-hole owning high nonlinearity, low flat-dispersion as well as low confinement losses have been obtained. The designed PCFs are applied in RFA as gain medium and numerical results indicate that flat gain covering 1536 nm ~1565 nm band can be obtained by optimizing the center-to-center spacing between the air-holes and the air-hole diameter of the PCFs.