Fiber-optic transmission has revolutionized global communications by offering unprecedented information capacities over distances that range from the domain of local area networks to that of trans-oceanic links. By progressively taking advantage of this great potential, optical systems have been able to accommodate an ever-increasing demand for data traffic, which in recent years has been boosted by the explosion of the Internet, with the most challenging bandwidth requirements coming from real-time and streaming applications (Netflix and YouTube are just two examples). Nevertheless, various reports point out a warring disparity between the exponential growth rate of the demand and that of the capacity of Wavelength-Division Multiplexed systems, which are facing either their technological limits or even their fundamental limits. The only approach to equalize this disparity is a sustainable parallelization of transmission systems, where sustainability implies that the increase in capacity comes along with a reduction of the cost per unit of information – the cost per bit. This approach is known as Space-Division Multiplexing (SDM), and it now constitutes one of the most fervid research areas in optical communications.
A key-concept in SDM research is “integrated parallelization,” and the ongoing debate on SDM aims to resolve the question of which SDM implementation will be the most sustainable. The implementation of SDM in FMFs and MCFs pushes this concept to its ultimate limit by integrating also multiplexed spatial light-paths in a single fiber. This approach has been intensively investigated in recent years, and although hero experiments have reported impressive results in terms of throughput, distance, and mode multiplicity, the practical implementation of SDM systems still entails several major challenges. One outstanding point is the lack of SDM field trials, which stems from the global absence of deployed SDM fibers. In fact, the aforementioned results were obtained in laboratory experiments by making use of spooled fiber samples in a controlled environment. On the contrary, demonstrating system operation in a realistic environment is an imperative step forward in the path towards SDM deployment.
This proposal aims to demonstrate SDM transmission beyond laboratory experiments, through extensive field trials. This revolutionary transition will be enabled by a synergy with project INCIPICT (, which will make available to FIRST a unique metropolitan area network based on deployed FMFs and MCFs. The mission of FIRST is to demonstrate mode-multiplexed transmission on the available SDM fiber types – FMFs and MCFs – in various regimes of operation. These include the case in which the fiber cores/modes interfere with one another, as well as the case in which they don’t. The former case requires relying to the use of coherent receivers and to the implementation of multiple-input-multiple-output technique that are necessary in order to extract the transmitted information.
The latter case is more suitable for the search of lower-complexity receiver schemes. Around the core objective, FIRST pursues other major goals that will contribute to a substantial advancement in the understanding and implementation of SDM systems. One is the devising of advanced techniques for the characterization of the main fiber propagation characteristics, which on one hand will enable the development of effective system performance monitoring techniques, and on the other hand will yield more realistic models for linear and nonlinear propagation effects. Another goal is the characterization and optimization of SDM devices, which includes amplifiers, multiplexers, and add/drop elements. FIRST targets also setting a historical benchmark for the performance of deployed SDM systems, as well as addressing the comparison between FMF and MCF transmission in the same application domain. A public library of measured data will be made freely available online, along with a software tool for the
design and test of SDM transmission schemes. Another outstanding goal of FIRST is the use of a novel receiver scheme, known as the Kramers-Kronig receiver, in conjunction with SDM, targeting low-complexity architectures for SDM receivers. Finally, in the domain of optical networking, FIRST aims to develop and implement for the first time YANG models for all system components, enabling a NETCONF-driven control of an SDM network.
The project activities are organized in five technical work-packages, each lead by a different unit. Results dissemination will be pursued though scientific publications, a project website, and an international workshop at the end of the project.
Each unit contributes to the consortium through complementary expertise and most of the necessary assets, thereby making the consortium extraordinarily qualified and reducing the risk of failure to a negligible level.