Spatial multiplexing: technology

Space division multiplexing (SDM) utilizing few-mode fibres or multicore fibres supporting multiple spatial channels, is currently under intense investigation as an efficient approach to overcome the current capacity limitations of high-speed long-haul transmission systems based on single mode optical fibres. In order to realize the potential energy and cost savings offered by SDM systems, the individual spatial channels should be simultaneously multiplexed, transmitted, amplified and switched with associated SDM components and subsystems. In this chapter, a review of recent progress on the implementation of various SDM technologies is provided and the latest strategies and trends are presented. In particular, integrated SDM amplifier technologies will be discussed in detail and the prospect of further scaling with respect to the number of spatial channels that can be amplified will be described