Adiabatically-tapered fiber mode multiplexers

Abstract

Simple all-fiber three-mode multiplexers were made by adiabatically merging three dissimilar single-mode cores into one multimode core. This was achieved by collapsing air holes in a photonic crystal fiber and (in a separate device) by fusing and tapering separate telecom fibers in a fluorine-doped silica capillary. In each case the LP01 mode and both LP11 modes were individually excited from three separate input cores, with losses below 0.3 and 0.7 dB respectively and mode purities exceeding 10 dB. Scaling to more modes is challenging, but would be assisted by using single-mode fibers with a smaller ratio of cladding to core diameter.

Ultrathin endoscopes based on multicore fibers and adaptive optics: a status review and perspectives

“…This is what is known as modal multiplexing in the context of telecommunications, and low-loss modal multiplexing has so far only been reported for up to six modes at a time. 51,52 As for chromatic dispersion, it is the phenomenon that the different colors travel at different velocities. It results in a temporal broadening of a pulse propagating on a given transverse mode and depends on the second derivative with respect to frequency of the propagation constant β of that mode.…”

Ultrafast-laser-inscribed 3D integrated photonics: challenges and emerging applications

“…In order to achieve mode selectivity in a photonic lantern, asymmetry has to be introduced. This breaks the degeneracy at the singlemode ports by using single-mode fibres of different propagation constants as demonstrated in a fibre lantern [156,157] and recently in an laser-inscribed lantern [158]. Using ultrafast laser inscription, asymmetry can simply be introduced by either writing waveguides of different size or by varying the index contrast via adjusting the laser power.…”

All-fiber fused directional coupler for highly efficient spatial mode conversion

“…Recently, a new approach suggested a device made by tapering few fibres which were then fused in a fluorine-doped silica capillary. In such configuration the fused fibres take the role of a core of a multimode fibre, in which three individual modes could be separately excited [20]. In this paper, therefore, we further explore the possibility of obtaining an efficient mode conversion into high order modes with high modal purity, by using asymmetric fiber couplers formed by fusing pre-tapered SMF and either two or four mode fiber (FMF).…”