Study of Raman Gain Coefficients of ITU-T Single-Mode Fiber Types

Raman amplified system offers optical signal gain with the lowest noise figure and is critical to meet the requirement of larger Optical-to-Signal-Noise Ratio (OSNR) employing advanced modulation formats (beyond 400G). The distributed Raman gain characteristics of the optical fiber strongly depend on the waveguide design parameters such as doping profile in the core region, modal effective area (Aeff), dispersion and attenuation coefficients. Therefore, we have investigated the Raman gain coefficients of all commercial ITU-T grade fibers (standards G.652.D, G.657.A2/B3, G.656/655 and G.654.E) commonly deployed in optical networks. Currently, G.654.E offers the lowest attenuation and larger tolerance to fiber nonlinearities and has been identified as the most suitable fiber for the multi-tera-rate transmission over ultra-long distances. However, the corresponding Raman gain coefficient was found to be ~ 50% lower than the standard G.652.D fibers. Our study can be used as a guideline for the selection of suitable fiber in the Raman amplified optical network links.