"MIMO communications over Multi-mode Fibers"

Speaker:

Peter Kairouz

Date and Time:

January 26, 2012 - 10:30am - 10:50am

Presentation Abstract:

In an information-intensive era, the demand for Internet bandwidth is constantly increasing. Multi-Input Multi-Output (MIMO) communication over Multi-mode fibers promises to boost the Internet supply.  Multi-mode fibers are generally used in short-range links where they are favored over single-mode fibers because of their relaxed connector alignment tolerances and their reduced transceiver connector costs. However, modal dispersion limits the bandwidth of the fiber due to the different speeds of the fields in different modes. Moreover, these fields can couple and exchange energy due to fiber non-idealities and vibrations.These limitations in addition to fiber non-linearities make the design and analysis of MIMO mutli-mode systems a challenging and exciting one. Furthermore, current multi-mode fibers (OM3 and OM4) have core radii between 50 and 62.5 micrometers thus allowing hundreds of modes to propagate through their core. Unfortunately, the system’s dimensions, as well as computational complexity reasons, prevent us from coupling hundreds of signals into the fiber. As a result, the user must resort to an input and output coupling scheme to couple a number of inputs at the transmitter side and extract a number of outputs at the receiver side. This presentation provides an overview of the existent coherent optical systems and the soon to be deployed coherent optical MIMO systems. In our study, we provide a new random channel model that takes input/output coupling into account as well as modal dispersion and modal coupling. We also provide capacity-optimal strategies for the design of these couplers when channel state information (CSI) is available at the transmitter and the designer has full control over the couplers. Finally, we quantify the capacity loss for the case when CSI is not available.