Yoshimichi Amma

Dense SDM (12-Core

We propose long-haul space-division-multiplexing (SDM) transmission systems employing parallel multiple-input multiple-output (MIMO) frequency-domain equalization (FDE) and transmission fiber with low differential mode delay (DMD). We first discuss the advantages of parallel MIMO FDE technique in long-haul SDM transmission systems in terms of the computational complexity, and then, compare the complexity required for parallel MIMO FDE as well as the conventional time-domain equalization techniques. Proposed parallel MIMO FDE that employs low baud rate multicarrier signal transmission with a receiver-side FDE enables us to compensate for 33.2-ns DMD with considerably low-computational complexity. Next, we describe in detail the newly developed fiber and devices we used in the conducted experiments. A graded-index (GI) multicore few-mode fiber (MC-FMF) suppressed the accumulation of DMD as well as intercore crosstalk. Mode dependent loss/gain effect was also mitigated by employing both a ring-core FM erbium-doped fiber amplifier and a free-space optics type gain equalizer. By combining these advanced techniques together, we finally demonstrate 12-core × 3-mode dense SDM transmission over 527-km GI MC-FMF without optical DMD management.

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The design and characteristics of a novel three-mode 12-core fiber are demonstrated. This fiber has low intercore crosstalk (IC-XT) and low differential mode group delay (DMD). In order to produce such a fiber, three new techniques are introduced to few-mode multicore fiber. A heterogeneous core arrangement with two types of cores, is used to minimize IC-XT; a multistep index, which can control DMD without sacrificing intermode crosstalk, is adopted as a core profile to reduce DMD; and a square lattice structure allows for the inclusion of 12 cores within a cladding diameter of 230 μm. Optimum design of the fiber using these techniques is determined from calculations. Finally, detailed characteristics of a three-mode 12-core fiber based on the design are reported. A fabricated 40-km fiber is confirmed to have a DMD of less than |530| ps/km over the C + L band and an estimated worst-case IC-XT of less than -55 dB/100 km at 1550 nm. This low IC-XT allows for the transmission of 32 QAM signals.

3-Mode) Transmission Over 527 km With 33.2-ns Mode-Dispersion Employing Low-Complexity Parallel MIMO Frequency-Domain Equalization

Multicore fibers and few-mode fibers have potential application in realizing dense-space-division multiplexing systems. However, there are some tradeoff requirements for designing the fibers. In this paper, the tradeoff requirements such as spatial channel count, crosstalk, differential mode delay, and cladding diameter are discussed. Further, the design concept and transmission characteristics of high-core-count single-mode multicore fibers are discussed. A heterogeneous multicore fiber with 30 cores and quasi-single-mode multi-core fibers with 31 cores are developed.

Few-Mode Multicore Fiber With 36 Spatial Modes (Three Modes (LP

An Ultra-high density cable with 12-core MCF was presented. A fabricated cable realized core density of 6 cores/mm2. The change of crosstalk behavior before and after cabling was moderate thanks to adequate cable design.

_{\bf 01}

We demonstrate 120.7-Tb/s SDM/WDM unrepeatered transmission over a 204-km 7-core fiber with aggregate spectral efficiency of 53.6 b/s/Hz using a remotely pumped 7-core EDFA and Raman amplification. 17.2-Tb/s (180 × 95.8 Gb/s) PDM-32QAM signals have been transmitted at each core.

, LP

We propose a kind of heterogeneous trench-assisted graded-index few-mode multi-core fiber with square-lattice layout. For each core in the fiber, effective area (A(eff)) of LP(01) mode and LP(11) mode can achieve about 110 μm(2) and 220 μm(2). Absolute value of differential mode delay (|DMD|) is smaller than 100 ps/km over C + L bands, which can decrease the complexity of digital signal processing at the receiver end. Considering the upper limit of cladding diameter (D(cl)) and cable cutoff wavelength of LP(21) mode in the cores located at the inner layer, we set core pitch (Λ) as 43 μm. In this case, D(cl) is about 220.4 μm, inter-core crosstalk (XT) is lower than -40 dB/500 km and the relative core multiplicity factor (RCMF) reaches 15.93.

_{\bf 11a}

We demonstrate the unrepeatered transmission of over 100 Tb/s by employing a multicore-fiber-based remote optically pumped amplifier. We establish 120.7-Tb/s, 204-km seven-core fiber transmission with the aggregate spectral efficiency (SE) of 53.6 b/s/Hz, a record capacity per fiber and the highest SE for unrepeatered transmission. We also realized the highest capacity per core of 17.2 Tb/s (180 × 95.8 Gb/s) and SE of 7.6 b/s/Hz by using the polarization-division-multiplexed 32-quadrature amplitude modulation format for unrepeatered transmission.

, LP

A homogeneous 31-core fibre with a cladding diameter of 230 μm for quasi-single-mode transmission is designed and fabricated. LP01-crosstalk of -38.4 dB/11 km at 1550 nm is achieved by using few-mode trench-assisted cores.

_{\bf 11b}

Fusion splice technique for multicore fiber was demonstrated. Low splice loss less than 0.1 dB in average was realized by using end-view alignment system and swing electrode system under small cleaved angle condition.

) × 12 Cores)

Multicore fibers and few-mode fibers have the potential to realize dense-space-division multiplexing systems. Several dense-space-division multiplexing system transmission experiments over multicore fibers and few-mode fibers have been demonstrated so far. Multicore fibers, including recent results by our group, are reviewed in this paper.