Application of Spatial Modes in Advanced Optical Communications and Networking

Abstract

To satisfy the ever-increasing demands for high speed networks, the spatial dimension is exploited to increase the capacity of the communication systems. Optical waves with spatial orthogonality can serve as independent transmission channels after they are multiplexed together, and this technique is called as spatial division multiplexing (SDM). SDM can be realized in both fiber and free space optical channels. Spatial modes can consist of: multiple parallel beams in a multicore fiber, different orders of the fiber’s eigenmodes in a multimode fiber, and orthogonal modes, such as Laguerre Gaussian modes. Although SDM is a very promising option to achieve a large capacity network, however there are still many problems to be solved before it can be implemented in real applications. In this dissertation, SDM is investigated from the transmission level to the network level perspective. In the first part of this dissertation, we have verified a strong correlation between the crosstalk intensity and the statistical characterization of the signal in optical fibers and developed a novel method for monitoring in-service channel crosstalk. Also, as for the application in the free space optical channels (FSO), by adopting the Kolmogorov model of turbulence we established and experimentally verified a relationship between the wavefront error variance and the phase structure function that can be directly applied to estimate the atmospheric coherence diameter and the refraction-index structure constant. The second part of the dissertation focuses on SDM employment in two relevant topologies of optical networks (i.e. metro/core segment and a comprehensive architecture that consists of core/metro and access network segments). We investigated and proposed an optimized design and assignment strategy for the resource allocation in multidimensional networking structure with plurality of spectral and spatial components that also includes a dynamic interaction between spectral and spatial modes.