Optimal design of 4LP-mode multicore fibers for high spatial multiplicity.

High spatial multiplicity fiber designs are presented for homogeneous and heterogeneous 4LP-mode multicore fibers (MCFs) that support six spatial modes per core. The high-spatial-density 4LP-mode MCF design methodology is explained in detail. The influence of the number of cores on the cladding diameter (D) and relative core multiplicity factor (RCMF) is investigated.

Heterogeneous trench-assisted few-mode multi-core fiber with graded-index profile and square-lattice layout for low differential mode delay.

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.

Heterogeneous trench-assisted few-mode multi-core fiber with low differential mode delay.

We propose a kind of heterogeneous multi-core fiber (Hetero-MCF) with trench-assisted multi-step index few-mode core (TA-MSI-FMC) deployed inside. After analyzing the impact of each parameter on differential mode delay (DMD), we design a couple of TA-MSI-FMCs with A(eff) of 110 μm2 for LP01 mode. DMD of each TA-MSI-FMC is smaller than |170| ps/km over C + L band and the total DMD can approach almost 0 ps/km over C + L band if we adopt DMD managed transmission line technique by using only one kind of Hetero-TA-FM-MCF.

409-Tb/s + 409-Tb/s crosstalk suppressed bidirectional MCF transmission over 450 km using propagation-direction interleaving.

We demonstrate bidirectional transmission over 450 km of newly-developed dual-ring structured 12-core fiber with large effective area and low crosstalk. Inter-core crosstalk is suppressed by employing propagation-direction interleaving, and 409-Tb/s capacities are achieved for both directions.

12-core fiber with one ring structure for extremely large capacity transmission.

The feature of a multicore fiber with one-ring structure is theoretically analyzed and experimentally demonstrated. The one-ring structure overcomes the issues of the hexagonal close-pack structure. The possibility of 10-core fiber with Aeff of 110 μm(2) and 12-core fiber with Aeff of 80 μm(2) is theoretically presented.

Large-effective-area uncoupled few-mode multi-core fiber.

Characteristics of few-mode multi-core fiber (FM-MCF) were numerically analyzed and experimentally confirmed. The cores of FM-MCF were designed to support transmission of LP(01) and LP(11) modes from the point of bending loss of LP(11) and LP(21) modes. Inter-core crosstalk between LP(11) mode was calculated to determine core pitch of fibers.

Design and analysis of large-effective-area heterogeneous trench-assisted multi-core fiber.

Based on the overlap integral of electromagnetic fields in neighboring cores, a calculating method is proposed for obtaining the coupling coefficient between two adjacent trench-assisted non-identical cores. And a kind of heterogeneous trench-assisted multi-core fiber (Hetero-TA-MCF) with 12 cores is proposed to achieve large effective area (A(eff)) and high density of cores. As bending radius becomes larger than 50 mm, the crosstalk value at 1550-nm wavelength of the Hetero-TA-MCF is about -42 dB after 100-km propagation and the A(eff) of this Hetero-TA-MCF can reach 100 µm(2).

Effectively single-mode all-solid photonic bandgap fiber with large effective area and low bending loss for compact high-power all-fiber lasers.

An effectively single-mode all-solid photonic bandgap fiber with large effective area and low bending loss for compact high-power all-fiber lasers is fully investigated. The pitch dependencies of effective area, bending loss, and effectively single-mode operation are discussed numerically and experimentally. The calculation results indicate that an effectively single-mode all-solid photonic bandgap fiber with an effective area of more than 500 μm(2) and a bending loss of less than 0.

1000-km 7-core fiber transmission of 10 x 96-Gb/s PDM-16QAM using Raman amplification with 6.5 W per fiber.

We demonstrate 7-core fiber transmission of 10 x 96-Gb/s PDM-16QAM signals over 1000-km using distributed Raman amplification (DRA). DRA gain of 9-12 dB and equivalent noise figure of less than 1 dB are achieved in all cores. We also prove the feasibility of high power multi-core fiber transmission with per fiber power of 6.

Low bending loss and effectively single-mode all-solid photonic bandgap fiber with an effective area of 650 μm2.

A large-mode-area all-solid photonic bandgap fiber with a seven-cell core and five high-index rod rings is investigated. Numerical simulations show that an effective area of more than 500 μm(2), a bending loss of less than 0.1 dB/m at a bending radius of 10 cm and effectively single-mode operation can be achieved simultaneously.

Selective mode excitation and discrimination of four-core homogeneous coupled multi-core fiber.

Coupled modes of homogeneous coupled multi-core fiber are selectively excited and discriminated utilizing the difference of equivalent propagation angle. To quantatively evaluate the extinction ratio (selectivity) of adjacent modes, a new mode discrimination technique is developed by measuring the visibility of far-field patterns under small change of wavelength of the launching beam. The peak angles of discriminated far-field patterns show a strong correlation with the incident angle of the launching beam, which means that the coupled modes were selectively excited and discriminated.

A large effective area multi-core fiber with an optimized cladding thickness.

The cladding thickness of trench-assisted multi-core fibers was theoretically and experimentally investigated in terms of excess losses of outer cores. No significant micro-bending loss increase was observed on multi-core fibers with the cladding thickness of about 30 µm. The tolerance for the micro-bending loss of a multi-core fiber is larger than that of the single core fiber.

Multi-core fiber design and analysis: coupled-mode theory and coupled-power theory.

Coupled-mode and coupled-power theories are described for multi-core fiber design and analysis. First, in order to satisfy the law of power conservation, mode-coupling coefficients are redefined and then, closed-form power-coupling coefficients are derived based on exponential, Gaussian, and triangular autocorrelation functions. Using the coupled-mode and coupled-power theories, impacts of random phase-offsets and correlation lengths on crosstalk in multi-core fibers are investigated for the first time.

UV-induced Bragg grating inscription into single-polarization all-solid hybrid microstructured optical fiber.

We demonstrate a single-polarization all-solid hybrid microstructured optical fiber with a UV-induced Bragg grating. A strong (∼20 dB) UV-induced Bragg grating was inscribed within the 30 nm-wide single-polarization window of the fiber, producing polarized Bragg reflection. The sharp band-edge cutoff allows a large polarization-extinction ratio of the Bragg reflection.

Observation of a propagation mode of a fiber fuse with a long-period damage track in hole-assisted fiber.

We examined the fiber-fuse propagation characteristics in hole-assisted fibers (HAFs) when the diameter of an inscribed circle linking the air holes was almost the same as the diameter of the melted area caused by the fiber fuse. We observed a new propagation mode for the fiber fuse in HAF with a damage track whose period was approximately 30 times longer than that in conventional single-mode fiber. We also made the first observation of a new threshold power (upper threshold) for the fiber fuse.

Single-polarization operation in birefringent all-solid hybrid microstructured fiber with additional stress applying parts.

We demonstrate single-polarization (SP) operation in a birefringent all-solid hybrid microstructured fiber that has additional boron-doped stress-applying parts (SAPs). The stress from the SAPs is added to the stress from the highly germanium-doped high-index regions, and SP operation with more than a 25 nm bandwidth was achieved at the shorter wavelength edge of the second bandgap.