Evolution of the beam diameter in a multimode fiber link through offset connectors

We find that using an overfilled launch, transmission of an 8-Gb/s nonreturn-to-zero (NRZ) signal can suffer a significant power penalty due to modal noise or fiber bandwidth fluctuations if an offset connector is located before the 300-m-long multimode fiber link. This is an important problem as multimode fiber links in the premises typically contain several (potentially offset) connectors. A possible solution in state-of-the-art multimode fibers having a small refractive index center defect is to employ a single-mode center launch. To evaluate the robustness of this technique in the presence of several offset connectors in the link, a thorough study of the evolution of the beam diameter is performed. It suggests that at least five standard connectors may be employed without incurring significant power penalties.