Spatially resolved detection and equalization of modal dispersion limited multimode fiber links

The authors present theoretical and experimental results of an optoelectronic-equalization technique that mitigates intersymbol interference caused by differential modal delay in multimode fiber. By exploiting the spatial diversity of the transverse optical-fiber modes, the authors are able to provide a sufficient additional information in the form of mode-dependent photocurrents to enhance total signal integrity. A fabricated two-segment photodetector is demonstrated with a routinely achievable two-times improvement in bandwidth-distance product. They also show the robustness of the technique to the expected variations in graded-index profiles.