Sebastian Randel

Mode-Division Multiplexing Over 96 km of Few-Mode Fiber Using Coherent 6

We report simultaneous transmission of six spatial and polarization modes, each carrying 40 Gb/s quadrature-phase-shift-keyed channels over 96 km of a low-differential group delay few-mode fiber. The channels are successfully recovered by offline DSP based on coherent detection and multiple-input multiple-output processing. A penalty of <;1.2 dB is achieved by using 6 × 6 feed-forward equalizers with 120 taps each. The 6 × 6 impulse-response matrix fully characterizing the few-mode fiber is presented, revealing the coupling characteristics between the modes. The results are obtained using mode multiplexers based on phase plates with a mode selectivity of >;28 dB.

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Mode-division multiplexing over 33-km few-mode fiber is investigated. It is shown that 6×6 MIMO processing can be used to almost completely compensate for crosstalk and intersymbol interference due to mode coupling in a system that transmits uncorrelated 28-GBaud QPSK signals on the six spatial and polarization modes supported by a novel few-mode fiber.

6 MIMO Processing

We demonstrate the transmission of 6 independent, spatially- and polarization multiplexed 28-Gb/s QPSK signals over 10 km of three-mode fiber using mode-selective excitation and full coherent 6 × 6 MIMO processing.

6×56-Gb/s mode-division multiplexed transmission over 33-km few-mode fiber enabled by 6×6 MIMO equalization

Low differential group delay (DGD) between the modes of a graded-index few-mode fiber is obtained by combining segments with DGD of opposite sign. Transmission of mode-multiplexed 6×20-GBd QPSK over a record distance of 1200 km is demonstrated.

Space-division multiplexing over 10 km of three-mode fiber using coherent 6 × 6 MIMO processing

We present a novel low-loss 3-spot mode coupler to selectively address 6 spatial and polarization modes of a few-mode fiber. The coupler is used in a 6×6 MIMO-transmission experiment over a 154-km hybrid span consisting of 129-km depressed-cladding and 25-km graded-index few-mode fiber.

Mode-multiplexed 6×20-GBd QPSK transmission over 1200-km DGD-compensated few-mode fiber

We summarize the latest advances in space-division multiplexing (SDM) for increasing the capacity per fiber strand. We discuss SDM fibers, recent SDM transmission experiments, subsystems suitable for SDM systems, as well as integrated components able to manipulate multiple spatial modes within a single optical device.

Low-loss mode coupler for mode-multiplexed transmission in few-mode fiber

We demonstrate high speed optical transmission systems using digital coherent detection at all-electronically multiplexed symbol rates of 80 and 107 Gbaud. At 107 Gbaud, we demonstrate a single-carrier polarization division multiplexed quadrature phase shift keyed (PDM-QPSK) line rate of 428 Gb/s. At 80 Gbaud, we achieve a single-carrier line rate of 640 Gb/s using PDM 16-ary quadrature amplitude modulation (16-QAM). Using two optical subcarriers, we demonstrate a 1-Tb/s optical interface and conduct long-haul wavelength-division multiplexed (WDM) transmission on a 200-GHz grid over 3200 km of ultra-large effective area fiber.

Breakthroughs in Photonics 2012: Space-Division Multiplexing in Multimode and Multicore Fibers for High-Capacity Optical Communication

We experimentally demonstrate simultaneous transmission of three spatially multiplexed 56-Gb/s polarization-division-multiplex quadrature phase-shift keying (PDM-QPSK) channels over 24 km of a strongly coupled three-core fiber. The resulting crosstalk of about -4 dB is almost completely removed by coherent multiple-input multiple-output (MIMO) processing.

High Symbol Rate Coherent Optical Transmission Systems: 80 and 107 Gbaud

We present experimental results for combined mode-multiplexed and wavelength multiplexed transmission over conventional graded-index multimode fibers. We use mode-selective photonic lanterns as mode couplers to precisely excite a subset of the modes of the multimode fiber and additionally to compensate for the differential group delay between the excited modes. Spatial mode filters are added to suppress undesired higher order modes. We transmit 30-Gbaud QPSK signals over 60 WDM channels, 3 spatial modes, and 2 polarizations, reaching a distance of 310 km based on a 44.3 km long span. We also report about transmission experiments over 6 spatial modes for a 17-km single-span experiment. The results indicate that multimode fibers support scalable mode-division multiplexing approaches, where modes can be added over time if desired. Also the results indicate that mode-multiplexed transmission distance over 300 km are possible in conventional multimode fibers.

MIMO-Based Crosstalk Suppression in Spatially Multiplexed 3

We demonstrate compensation of fiber nonlinearities using optical phase conjugation of an 8-channel WDM 32-Gbaud PDM QPSK signal. Conjugating phase every 600 km in a fiber loop enabled a 6000 km transmission over TrueWave fiber.