Denis Molin

Multimode Optical Fibers

Usually speckles of radiation of multimode optical fibers esteem as spatially isotropic, that confirms by numerousexperimental data presented in the literature. However, from general reasons follows, that for the ideal dielectriccylindr, where is the cylindrical symmetry of fields of all waveguide modes, the anisotropy of speckles of outputradiation should show in some cases. Present activity is dedicated to the theoretical and experimental researches of

Few-Mode Fibers for Mode-Division-Multiplexed Systems

We describe the design trade-offs that are at stake when optimizing few-mode fibers (FMFs) that support a high number (≥ 6) of LP modes. We particularly detail the design of 6-LPmode fibers that allow to multiply the capacity by a tenfold factor (two modes being spatially non-degenerate and four modes being two times spatially degenerate). For low-differential-mode-groupdelay (low-DMGD) FMFs adapted to strongly-coupled modedivision-multiplexed systems, trench-assisted graded-index-core profiles can be optimized to have Max|DMGD| <;10 ps/km and undesired leaky LP modes appropriately cut off, while all guided LP modes show good robustness (Bend Losses <;10 dB/turn at 10 mm bend radius). Such low-DMGD FMFs being sensitive to process variability, we show how fiber concatenations can efficiently compensate for this issue and that values <;25 ps/km can realistically be reached. For weakly-coupled FMFs adapted to weakly-coupled mode-division-multiplexed systems, step-index-core profiles can be optimized to have large effective index differences, Δneff, between the LP modes (Min|Δneff | >1.0 × 10-3) to limit mode coupling and Aeff >~100 μm2 to limit intra-mode non-linearity with good mode robustness. For such weakly-coupled FMFs, sensitivity to process variability is small and main characteristics do not significantly change when variations are within the manufacturing tolerances. We also briefly discuss experimental validations.

Low-DMGD 6-LP-mode fiber

We report the design and the fabrication of a low-DMGD 6-LP-mode fiber adapted to strongly-coupled mode-division-multiplexed systems that allows to multiply the capacity by a tenfold factor.

Compensation of Chromatic Dispersion by Modal Dispersion in MMF- and VCSEL-Based Gigabit Ethernet Transmissions

Multimode vertical-cavity surface-emitting lasers (VCSELs) with large spectral widths are widely used with multimode fibers (MMFs) in Gigabit Ethernet (GbE) systems. MMFs exhibit large chromatic dispersion values that can strongly impact the performance of these systems for high bit rates and/or long distances. Here, we show that in 10-GbE systems using VCSELs and MMFs, the chromatic dispersion can be compensated for by the modal dispersion of the MMF.

Low-Differential-Mode-Group-Delay 9-LP-Mode Fiber

We report the fabrication of low-differential-mode-group-delay 9-LP-mode fibers using a standard bend-insensitive 50μm-diameter-core multimode process. Such 9-LP-mode fibers exhibit DMGDs <; 155ps/km at 1550nm.

Low-differential-mode-group-delay 9-LP-mode fiber

We report the optimization of a few-mode fiber, adapted to multiple-input multiple-output mode division multiplexing, that supports 9 LP modes (15 spatial modes). The fiber is fabricated using standard multimode processes, which allows for tight process tolerances, yielding low differential mode group delays (<;155 ps/km) with low attenuations (<;0.22 dB/km), large effective areas (≥95 μm2) and low bend losses.

10-Mode mode-multiplexed transmission over 125-km single-span multimode fiber

We demonstrate combined wavelength- and mode-multiplexed transmission over a 125-km multimode single span composed of 10- and 15-mode fibers with a spectral efficiency of 29 b/s/Hz. A transmission capacity of 115.2 Tb/s is achieved over a distance of 87 km.

Physical Modeling of 10 GbE Optical Communication Systems

A physical model of 10 Gigabit Ethernet (GbE) optical communications systems based on 50-μm graded-index multimode fibers (MMFs) is presented in this paper. It includes a model of vertical cavity surface emitting lasers (VCSELs) that accounts for the spatiotemporal dynamic of such transversally multimode lasers, commonly used in 10 GbE optical systems, and an accurate MMF model. This complete model is compared to the 10 GBASE-S Link Budget Spreadsheet developed within the IEEE P802.3ae 10 GbE Task Force and to experimental transmissions. Finally, VCSEL-to-MMF interactions and their impacts on 10 GbE transmissions are detailed and explained.

50 μm Multimode Fibers for Mode Division Multiplexing

50-μm-diameter graded-index core multimode fibers can be adapted to mode-division-multiplexed transmissions that use multiple-input-multiple-output digital signal processing and selective mode multiplexing. We realize and characterize such fibers and compare them to low-differential-mode-group-delay few-mode fibers.

10 Spatial mode transmission using low differential mode delay 6-LP fiber using all-fiber photonic lanterns.

To unlock the cost benefits of space division multiplexing transmission systems, higher spatial multiplicity is required. Here, we investigate a potential route to increasing the number of spatial mode channels within a single core few-mode fiber. Key for longer transmission distances and low computational complexity is the fabrication of fibers with low differential mode group delays. As such in this work, we combine wavelength and mode-division multiplexed transmission over a 4.45 km low-DMGD 6-LP-mode fiber by employing low-loss all-fiber 10-port photonic lanterns to couple light in and out of the fiber. Hence, a minimum DMGD of 0.2 ns (maximum 0.357 ns) is measured after 4.45 km. Instrumental to the multi-mode transmission system is the employed time-domain-SDM receiver, allowing 10 spatial mode channels (over both polarizations) to be captured using only 3 coherent receivers and real-time oscilloscopes in comparison with 10 for conventional methods. The spatial channels were unraveled using 20 × 20 multiple-input multiple-output digital signal processing. By employing a novel round-robin encoding technique, stable performance over a long measurement period demonstrates the feasibility of 10x increase in single-core multi-mode transmission.