Spatial Multiplexing in Multimode Fiber using Adaptive Optical or Digital Signal Processing

Stanford University, Stanford CA

Investigators

Abstract

The objective of this research is to develop techniques for increasing transmission capacity in both short-reach and long-reach fiber networks. The approach is to use spatial multiplexing in multimode fiber, which is a form of multi-input, multi-output transmission. Intellectual Merit: Short-reach fiber systems, such as data-center and local-area networks, already use multimode fiber with direct detection, but are limited by modal dispersion to only 10 Gbit/s per fiber. Adaptive optical signal processing will be used to prevent modal dispersion and enable spatial multiplexing in these systems. The approach developed in this project will simultaneously overcome modal dispersion and achieve multiplicative capacity gains in direct-detection systems. Longer-reach systems currently use single-mode fiber, and are now using coherent detection, which preserves information on phase and polarization of optical signals. Adaptive digital signal processing techniques will be developed to compensate modal dispersion and enable spatial multiplexing. Mode-dependent fiber losses and amplifier gains can cause signal fading, as in wireless systems. System-level approaches, such as modal-frequency diversity and space-time coding, will ensure reliability without significantly sacrificing multiplexing gain. Fundamental diversity-multiplexing tradeoffs will be studied. Broader Impacts: This project will enable dramatic increases in optical transmission capacity, and will help lower the cost per bit, benefiting research, education, healthcare, commerce, and security. New applications of multimode media will be enabled, complementing single-mode media. New connections between optical and wireless communications will be made, inspiring engineers in both fields. High-school students will be exposed to current research. Undergraduate and graduate students from diverse backgrounds will receive research training. Results of research will be integrated into undergraduate and graduate curricula.