We review the latest advances on ultra-high throughput transmission using crosstalk-limited single-mode multicore fibers and compare these with the theoretical spectral efficiency of such systems. We relate the crosstalkimposed spectral efficiency limits with fiber parameters, such as core diameter, core pitch, and trench design. Furthermore, we investigate the potential of techniques such as direction interleaving and high-order MIMO to improve the throughput or reach of these systems when using various modulation formats.
We describe a number of experiments demonstrating and exploring the potential of combing wideband-optical comb sources with space-division multiplexed transmission systems and in particular with homogeneous-single-mode multicore fibers including Pb/s transmission using conventional receiver technology without MIMO processing and longdistance recirculating transmission. We describe experiments using synchronized parallel transmission loops to investigate joint processing of spatial super channels and multi-dimensional modulation before discussing how optical comb technology may combine with SDM fibers to allow comb re-generation across networks to enable high-order modulation with simplified DSP. Overall, these experiments demonstrate a range of scenarios where the combination of optical combs and homogeneous MCFs can be advantageous in future optical communications networks.
<p> Due to the ever increasing capacity demands for optical communication links, single-mode fibers will soon not be able to support the exponential growth of data rates. A strong candidate to overcome the upcoming capacity crunch is spacedivision multiplexing (SDM) where different parallel paths in one fiber are used to transmit independent data streams. Suitable candidates for SDM are e.g. multi-mode fibers (MMF), where different orthogonal modes are independently addressed. In this paper, we discuss nonlinear interaction between signals that propagate in different fiber modes. Based on the nonlinear effect of four-wave mixing, phase-matching between spectral components that propagate in different fiber modes is studied. With the knowledge of intra- and intermodal four-wave mixing, all Kerr-effect based nonlinearities can be expressed in an analytical way. We propose a method to calculate the maximal achievable Optical Signal to Noise Ratio (OSNR) for each mode, based on the assumption that the nonlinear interference can be taken into account for by an additive noise term. </p><p> We analyzed a sample transmission link that uses a 55-mode graded-index multi-mode fiber, aiming to minimize the group-delay differences between signals that travel in different fiber modes. It is shown that each of the 55 modes can achieve an equal or higher OSNR compared to a standard single-mode fiber. </p>