A Spatiotemporal Communication Architecture for Fiber Optic Few-Mode Systems

Optical fibers are ubiquitous in today’s communication networks and are even becoming more prevalent thanks to their promising features such as low loss, high-bandwidth, and high security. Optical fiber has already done a lot to facilitate the fast transmission of information across long distances. Such technology is different than communication systems of old and the wireless network systems of today. For example, optical fiber affords a user more reliability and security while RF systems retain a susceptibility to jamming and eavesdropping that must be mitigated. In the last half-century, a revolution has occurred in the field of communication systems. Subsequently, the facilitation of optical transmission has emerged in the domains of time, wavelength, mode, and “code” among many others. Mode-division multiplexing (MDM) is one way to improve optical throughput through fibers creating multiple channels of communication.

This thesis addresses the detection and sorting of optically transmitted information that makes use of a spatial MDM scheme but also combines it with a standard communications model to create a spatiotemporal system. The challenge herein is to devise a scheme that combines the temporal aspect of communication systems with the spatial profile of the electric field that also carries the information. We take advantage of the fiber’s cross-section which consequently allows us to model each mode profile as an “image” and sample it accordingly using a photodetector array. This architecture makes use of a quasi-orthogonal mode model with user coupling among each mode. In this way, we can create an integrative communication architecture that incorporates the coupling between users. We also propose a robust way of multiuser detection that recovers all user input bitstreams and optimizes the way in which users are positioned for the best system performance.

This is my Master's Thesis