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This work presents results of design of precision spatial positioning scheme for mode division multiplexing (MDM) system channels over the core end of multimode optical fiber (MMF) with extremely enlarged core diameter up to 100 μm. Proposed solution is based on so-called “mode field matching centralized launching” technique that provides reducing differential mode delay (DMD) by equalization of launched and excited fundamental mode field radiuses (MFR). Unlike to known solution, it is proposed to localize the combination of injected MFR and precision radial offset launching conditions that would provide transmission almost total injected MDM mode channel power to only the one particular excited fiber mode with the same azimuthal order. Recently proposed method for design of described MDM-multiplexer channel spatial positioning scheme is based on combination of well known overlap integral method and earlier on developed Gaussian approximation modification, generalized for analysis of silica weakly guiding optical fibers with one outer solid cladding and arbitrary axially-symmetric refractive index profile. The last one provides a passage to analytical expressions for any order mode coupling coefficients, under taking into account inserted precision radial misalignment. This work is concerned with research of silica 100-μm-core MMF with refractive index profile corresponding to graded index profile of typical real commercially available MMFs of ISO/IEC Cat. OM2+/OM3, scaled up to 100-μm-core that differs by smoothed form and does not contain any strong distortions or defects. The paper presents results of computation of 7-mode and 5-mode MDM multiplexer channel spatial positioning scheme over described above 100-μm-core MMF by taking into account only selected mode excitation under elimination of “unwanted” modes with great DMD, detected by analysis of mode staff DMD diagram.
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