6. Conclusions

In this article, we have discovered or rediscovered some of the special features of multimode or multicore optical fibers. The multiplicity of spatial paths, sometimes perceived as a limitation, now appears to be a real asset, not least because of the technological means available today to exploit them. In particular, we have studied the case of fiber-optic transmissions where, in parallel with the ongoing performance optimization of multimode fibers, slightly multimode and multicore fibers are enabling an impressive leap forward in terms of capacity. The implementation of these new fibers is based on almost 50 years of innovation in the manufacture of the fibers themselves, and in the optical and photonic technologies used to exploit them. This is a very active area of research today in the academic and industrial community, and there is no doubt that some of these fibers will soon be...