Trench-assisted Multi-core Fiber Research Articles

Randomly coupled trench-assisted multicore fibers with different arrangements for high tolerance of manufacturing errors

Randomly coupled trench-assisted multicore fibers with different arrangements for high tolerance of manufacturing errors

Performance evaluation of trench-assisted multi-core fiber for passive optical network

Performance evaluation of trench-assisted multi-core fiber for passive optical network

Design of M-type core trench-assisted multi-core fiber with a cladding diameter of 200 µm for low-crosstalk long-haul transmission

The design of homogenous trench-assisted multi-core fiber with M-type cores and a cladding diameter of 200 µm is proposed by numerical simulations. The M-type core is introduced to reduce the inter-core crosstalk (XT) of a 19-core fiber to below −30 dB/100 km with a low cost of cutoff wavelength. At the same time, the trade-off between the XT suppression and the effective area of the fundamental mode is mitigated to ensure the effective area is larger than 70 μm2 to suppress the non-linear effects. The study of the effects of the high-index ring of the M-typed core on the XT, effective area, and power fraction shows the potential in improving the fiber performance by a well-designed micron structure of the core. The bending performance shows this design can operate with low loss and crosstalk, and an effective area of over 70 μm2 at a bending radius from 15 mm to 500 mm. The proposed design provides the possibility to improve the MCF performance for long-haul transmission.

Review on high capacity transmission with multi core fibers

This paper describes cases where the new type of fiber called Multi-core fiber that can resolve the current Internet capacity transmission problems with low crosstalk and attenuation. India is a data-hungry country, and with the help of the Internet, it's moving towards a strong economy and a digital India. A few years ago, no one knew that such a type of digitalization would occur and India would participate in it so rapidly. Currently, the world is moving towards basic phones to Smart Phones, Broadband, Wi-Fi equipment, Over the Top Platforms, IT Hub formation, and much more internet traffic is ongoing, so transmission with standard single-core cable is very tough. Multi Core Fiber (MCF) can resolve this problem. This article, looks at all of the options for multi-core fibers, particularly trench-assisted multi-core fibers.

A kind of single trench 19-core single-mode heterogeneous fiber with low crosstalk and anti-bending performance

The rapid growth of the demand for optical communication capacity promotes optical fiber communication technology. As a method to break through the capacity limitation of conventional single-mode fiber, multi-core fiber based on space division multiplexing technology has attracted extensive attention. In order to respond to the capacity of traditional single-mode fiber positively, we design a scheme of single-mode multi-core fiber combining the arrangement of heterogeneous fiber cores with secondary structure of low refractive index trench. The scheme consists of nineteen fiber cores arranged in a hexagonal closed-packed structure. Heterogeneous trench-assisted multi-core fiber (Hetero-TA-MCF) has low inter-core crosstalk and excellent anti-bending performance. Compared with conventional single-mode fiber, the Hetero-TA-MCF has the large transmission capacity and average effective area of each core of about 80 μm<sup>2</sup>. The transmission capacity of 19 cores is equivalent to the sum of the transmission capacities of 19 single-core single-mode fibers. We use COMSOL Multiphysics to simulate the fiber structure, finding the parameters that affect the properties of the fiber, selecting parameters and structures for optimal performance. Then we calculate the transmission characteristics by the finite element method,and the results of substantive simulating compute are as follows. The Hetero-TA-MCF achieves a low inter-core crosstalk (XT) of about –39 dB/100 km so that each core can be transmitted as a separate channe. It meets the standard of multi-core fiber long distance transmission. The XT of the heterogeneous 19-core single-mode fiber is suitable for multi-core fiber long distance transmission standards. The bending loss of the outermost fiber core is –7.7×10<sup>–5</sup> dB/m when the bending radius is 10 cm, which reflects the low loss characteristics of the structure. The nonlinear coefficients of three kinds of core are 1.28 W<sup>–1</sup>·km<sup>–1</sup>, 1.31 W<sup>–1</sup>·km<sup>–1</sup>, and 1.30 W<sup>–1</sup>·km<sup>–1</sup> respectively, reducing the nonlinear effect of optical fiber effectively; the dispersions of three kinds of cores are less than 24 ps/(nm·km). In addition, the steady single-mode transmission is achieved in <i>C</i>+<i>L</i> band. Compared with traditional single-mode fiber and single-trench homogeneous fiber, the proposed fiber in this work has low crosstalk, good bending resistance and large mode field area, which is suitable for long distance and large capacity transmission in space division multiplexing system.

Design and analysis of uncoupled heterogeneous trench-assisted multi-core fiber (MCF)

Abstract In this paper, author has presented design strategies for two core uncoupled heterogeneous multi-core fiber (MCF) to achieve minimum crosstalk. Authors have studied the variation of crosstalk between the cores in respect to the MCF parameters like bending radius, wavelength, core position and fiber length, so that single mode propagation can be made through designed uncoupled heterogeneous cores. The other important performance parameters of MCF i.e. group delay and dispersion have also been discussed in the paper.

Design and cross talk optimization in single-mode high-core count multicore fiber under limited cladding diameter

To achieve the minimum cladding diameter (CD) at fixed cladding thickness (35 μm) in the trench-assisted (TA) homogeneous multicore fibers (MCFs), five different core structures have been proposed under the single-mode propagation condition. The high-core counts, up to 37 cores with dense hexagonal closed packing arrangement of homogeneous cores have been considered for the analysis. The expression for cross talk (XT) under bending and twisting conditions has been derived using conventional method. The influence of core pitch, fiber length, fiber bending, twisting, and trench depth has also been exhibited on the XT performance for fundamental (LP01) mode propagation. The optimal CD based on specific values of cladding thickness and core pitch has been estimated in all the respective core structures for the target XT value of < − 50 dB / 100 km. The dispersion properties have also been investigated for all the proposed core structure, which is obtained nearly as −6 ps / nm-km at operating wavelength of 1550 nm. Further, in anticipation of high transmission capacity, the 61-core TA MCF has been analyzed for the XT performance under the limited CD of 300 μm.

Design of 125-μm cladding diameter multicore fibers with high core multiplexing factor for wideband optical transmission

Abstract We propose improved design of heterogeneous trench-assisted multicore fibers (MCFs) for wideband space division multiplexing (SDM) optical transmission. By adopting different parameters for heterogeneous cores, the trade-off among the effective area (Aeff), cut-off wavelength (λcc), and crosstalk (XT) was balanced. Different optimization approaches for long-haul and short-reach transmission applications have been adopted. A 125-μm cladding diameter 6-core fiber with Aeff = 90 μm2, λcc = 1300 nm and XT

Design and Analysis of Beam Steering Multicore Fiber Optical Switches

The design and performance characteristics of a beam steering optical switch for multicore fibers (MCFs) are reported. Port count, core count, transmission crosstalk, or a combination thereof can be optimized for the required application. Decreasing port separation or increasing the maximum steering angle both increase port count, whilst a higher core count or larger mode field diameter increase port capacity or port count, respectively, at the expense of greater intercore crosstalk. Potential losses from system misalignments and fiber fabrication variations in the core pitch are also estimated. A 50 port switch is possible for a 25 $\mu$ m core pitch 7 core hexagonal trench assisted MCF (TA-MCF) with a total mean statistical crosstalk on the central core of $-$ 25 dB after 1 km, assuming an operational wavelength of 1550 nm and maximum collimator actuator angle of 10 $^{\circ }$ . In contrast, a high capacity 25 $\mu$ m core pitch 61 core hexagonal TA-MCF can still offer up to a 5 port switch for the same level of crosstalk. For longer link distances, $-$ 25 dB crosstalk after 100 km (metro network) is achievable for a 50 port switch using a 35 $\mu$ m core pitch 7 core TA-MCF. Similar levels of crosstalk can be accomplished at 1000 km (core network) for a 41 port switch using a 25 $\mu$ m core pitch 7 core TA-MCF.

Highly sensitive measurement of surrounding refractive index using tapered trench–assisted multicore fiber

Abstract In this study, a surrounding refractive index (SRI) sensor based on tapered trench-assisted multicore fiber (TAMCF) is proposed and experimentally demonstrated. A segment of TAMCF was spliced between two single mode fibers (SMF28). Electric arc discharge technique was employed to fabricate a tapered sensor with a SMF28–tapered TAMCF–SMF28 structure. Numerical beam propagation was used to investigate the benefit of tapering on TAMCF. Tapering allows coupling of light in the center and outer cores, thereby enhancing the sensitivity of the sensor. Two sensors were fabricated with waist lengths of 10 and 15 mm and a waist diameter of 25 µm. The sensitivity of sensors at different SRI ranges was investigated using a set of honey/water solutions with precisely controlled concentrations. The measured SRI sensitivity was up to 35089.28 nm/RIU (refractive index unit) in SRI range from 1.4430 to 1.4442, which is higher than previously reported studies using other kinds of MCF sensors. SRI sensitivity was enhanced with the increase in waist length of the tapered TAMCF. The fabricated sensors have demonstrated good linearity in terms of spectral wavelength shift versus SRI variations.

Trench-Assisted Multicore Fiber with Single Supermode Transmission and Nearly Zero Flattened Dispersion

A trench-assisted multicore fiber (TA-MCF) with single-supermode transmission and nearly zero flattened dispersion is proposed herein. By adding a simplified microstructure cladding with only one ring of low-index inclusions on the basis of the multicore fiber, the microstructure cladding and mode-coupling mechanism were jointly employed into the TA-MCF to modulate light transmission. This guarantees that the TA-MCFs had sufficient capability for wideband dispersion management when only pure, germanium-doped, and fluorine-doped silica glass with low index differences were chosen to form the TA-MCF. Analyses also revealed that the TA-MCFs have the merits of shorter cut-off wavelength and flatter-top optical intensity distribution compared with traditional multicore fibers. After the investigation of the structural parameters’ influences on the dispersion of the fundamental supermode, two TA-MCFs with single-supermode transmission and nearly zero flattened dispersion were designed. For the seven-core TA-MCF, the dispersion varying from −0.46 to 1.35 ps/(nm·km) in the wavelength range of 1.50 to 2.04 μm, with bending loss as low as 0.085 dB/km and 35-mm bending radius at 1550 nm was achieved with index difference less than 0.015. The TA-MCFs proposed herein have the advantages of being a quasi-single material, with an all solid scheme and simplified structure.

Space-Division Multiplexing in Data Center Networks: On Multi-Core Fiber Solutions and Crosstalk-Suppressed Resource Allocation

The rapid growth of traffic inside data centers caused by the increasing adoption of cloud services necessitates a scalable and cost-efficient networking infrastructure. Space-division multiplexing (SDM) is considered as a promising solution to overcome the optical network capacity crunch and support cost-effective network capacity scaling. Multi-core fiber (MCF) is regarded as the most feasible and efficient way to realize SDM networks, and its deployment inside data centers seems very likely as the issue of inter-core crosstalk (XT) is not severe over short link spans (<1 km) compared to that in long-haul transmission. However, XT can still have a considerable effect in MCF over short distances,which can limit the transmission reach and in turn the data center’s size. XT can be further reduced by bi-directional transmission of optical signals in adjacent MCF cores. This paper evaluates the benefits of MCF-based SDM solutions in terms of maximizing the capacity and spatial efficiency of data center networks. To this end, we present an analytical model for XT in bi-directional normal step-index and trench-assisted MCFs and propose corresponding XT-aware core prioritization schemes. We further develop XT-aware spectrum resource allocation strategies aimed at relieving the complexity of online XT computation. These strategies divide the available spectrum into disjoint bands and incrementally add them to the pool of accessible resources based on the network conditions. Several combinations of core mapping and spectrum resource allocation algorithms are investigated for eight types of homogeneous MCFs comprising 7–61 cores, three different multiplexing schemes, and three data center network topologies with two traffic scenarios. Extensive simulation results showthat combining bi-directional transmission in dense core fibers with tailored resource allocation schemes significantly increases the network capacity. Moreover, a multiplexing scheme that combines SDM and WDM can achieve up to 33 times higher link spatial efficiency and up to 300 times greater capacity compared to a WDM solution.

Design and optimization of 32-core rod/trench assisted square-lattice structured single-mode multi-core fiber.

We propose and design a kind of heterogeneous rod-assisted and trench-assisted multi-core fiber (Hetero-RA-TA-MCF) with 32 cores arranged in square-lattice structure (SLS), and then we introduce the design method for Hetero-RA-TA-MCF. Simulation results show that the Hetero-RA-TA-32-Core-Fiber achieves average effective area (Aeff) of about 74 μm2, low crosstalk (XT) of about -31 dB/100km, threshold value of bending radius (Rpk) of 7.0 cm, relative core multiplicity factor (RCMF) of 8.74, and cable cutoff wavelength (λcc) of less than 1.53 μm.

Design of Homogeneous Trench-Assisted Multi-Core Fibers Based on Analytical Model

We present a design method of homogeneous trench-assisted multicore fibers (TA-MCFs) based on an analytical model utilizing an analytical expression for the mode coupling coefficient between two adjacent cores. The analytical model can also be used for crosstalk (XT) properties analysis, such as XT reduction amount versus trench width, trench depth, and other fiber structural parameters as compared with normal step-index MCFs. Furthermore, the model can be used to search for core positions for further XT reduction in nonclose-packed structures. For instance, we show that a dual-ring structure is the quasi-optimum core layout starting from an one-ring structured 12-core fiber. Based on the analytical model, a square-lattice structured 24-core fiber and a 32-core fiber are designed both for propagation-direction interleaving (PDI) and non-PDI transmission schemes. The proposed model provides a powerful tool for designing high-count homogeneous TA-MCFs.

Rectangular Array Multicore Fiber Realizing Low Crosstalk Suitable for Next-Generation Short-Reach Optical Interconnects With Low Misalignment Loss

Toward the next-generation exa-scale short-reach optical interconnects (OIs) supporting large-capacity data transmission, a compact computer-compatible 8-core heterogeneous trench-assisted multicore fiber (TA-MCF) is proposed, in which cores are arranged in a rectangular array. To analyze the crosstalk (XT) between adjacent cores of TA-MCF OI, a rigorous full-vectorial H- field finite element method (FEM) and coupled power theory are applied. The impact of various trench design parameters on the mode-coupling coefficient C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mn</sub> and the coupling length L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> is discussed in detail. An accurate explicit condition for the achievement of low XT in an 8-core heterogeneous TA-MCF OI is obtained through numerical simulations. A rigorous modal solution approach based on the computationally efficient FEM and the least squares boundary residual method is employed to analyze the coupling loss caused by the misalignment to a butt-coupled TA-MCF OI.

An Efficient Core Selection Method for Heterogeneous Trench-Assisted Multi-Core Fiber

We introduce an efficient core selection method for heterogeneous trench-assisted multi-core fiber. In order to make the design more flexible, the relative position and the width of one trench are usually assumed to have a proportional relation to core radius. However, it is hard to choose non-identical cores simultaneously, since cores are selected under the requirement of cable cutoff wavelength of higher order mode that is influenced by the surrounding trenches, whose relative position and width are also decided by core radii. Therefore, in this method, we first decide the cores at the outer layer and second obtain a core selection region for cores at the inner layer with the outer cores fixed. Both outer and inner cores are designed to achieve the target effective area and crosstalk.

Multicore optical fibres for next generation telecommunication transmission systems and components

We report on a new type of multicore fibres dedicated to a new generation of telecommunication networks. We designed and fabricated seven core fibres for (i) passive signal transmission, (ii) signal amplification and (iii) 1×7 signal division. In each case, the same cores and air-holes arrangement is used. However different operation is achieved by employing different cores doping and varying structural parameters of fibre, such as air-holes and cores diameters. We present experimental results of measurements performed for developed multicore fibres and multicore fibre components. Full Text: PDF References D.J. Richardson, J.M. Fini, L.E. Nelson, "Space-division multiplexing in optical fibres", Nat. Photonics 7, 354 (2013). CrossRef R.G.H. van Uden et al., "Ultra-high-density spatial division multiplexing with a few-mode multicore fibre", Nat. Photonics 8, 865 (2014). CrossRef H. Takara et al., "1.01-Pb/s (12 SDM/222 WDM/456 Gb/s) Crosstalk-managed Transmission with 91.4-b/s/Hz Aggregate Spectral Efficiency", ECOC Tech. Dig. 3, paper Th.3.C.1. (2012). CrossRef H. Takara et al., "1000-km 7-core fiber transmission of 10 x 96-Gb/s PDM-16QAM using Raman amplification with 6.5 W per fiber", Opt. Expr. 20, 10100 (2012). CrossRef M. Koshiba, K. Saitoh, Y. Kokubun, "Heterogeneous multi-core fibers: proposal and design principle", IEICE Electron. Expr. 6, 98 (2009). CrossRef Y. Kokubun, T. Watanabe, "Dense heterogeneous uncoupled multi-core fiber using 9 types of cores with double cladding structure", 17th Microoptics Conference, Sendai, (2011). DirectLink J. Tu et al., "Optimized Design Method for Bend-Insensitive Heterogeneous Trench-Assisted Multi-Core Fiber With Ultra-Low Crosstalk and High Core Density", J. Light. Technol. 31, 2590 (2013). CrossRef B. Yao et al., "Reduction of Crosstalk by Hole-Walled Multi-Core Fibers", Optical Fiber Communication Conference and Exposition (OFC/NFOEC) OFC, Los Angeles (2012). CrossRef K. Imamura et al., "Multi-core holey fibers for ultra large capacity wide-band transmission", 34th European Conference on Optical Communication (2008). CrossRef K. Saitoh, Y. Tsuchida, M. Koshiba, "Bending-insensitive single-mode hole-assisted fibers with reduced splice loss", Opt. Lett. 30, 1779 (2005). CrossRef A. Ziolowicz et al., "Hole-assisted multicore optical fiber for next generation telecom transmission systems", Appl. Phys. Lett. 105, 081106 (2014). CrossRef

Simple analytical expression for crosstalk estimation in homogeneous trench-assisted multi-core fibers.

An analytical expression for the mode coupling coefficient in homogeneous trench-assisted multi-core fibers is derived, which has a simple relationship with the one in normal step-index structures. The amount of inter-core crosstalk reduction (in dB) with trench-assisted structures compared to the one with normal step-index structures can then be written by a simple expression. Comparison with numerical simulations confirms that the obtained analytical expression has very good accuracy for crosstalk estimation. The crosstalk properties in trench-assisted multi-core fibers, such as crosstalk dependence on core pitch and wavelength-dependent crosstalk, can be obtained by this simple analytical expression.

Optimized Design Method for Bend-Insensitive Heterogeneous Trench-Assisted Multi-Core Fiber With Ultra-Low Crosstalk and High Core Density

We describe and explain the design methods for the cores, trench layers and core number in multi-core fibers (MCFs) in detail. According to such method, we propose relative optimized design schemes for heterogeneous trench-assisted multi-core fiber (Hetero-TA-MCF), inside which cores are arranged in one-ring structure. This Hetero-TA-MCF is a kind of bend-insensitive MCF with high density of cores and ultra-low crosstalk.

Mode-coupling analysis and trench design for large-mode-area low-cross-talk multicore fiber

The complete analytical solutions of the mode-coupling dynamics for seven-core multicore fibers (MCFs) with identical cores is proposed. All the coupling coefficients C(mn) of adjacent cores and nonadjacent cores as a function of the structural parameters are investigated. It is shown that the coupling coefficients can decrease by adjusting the structural parameters. In addition, the trench-assisted structure could be used for suppressing cross talk in MCF, and the effective area A(eff) can be enlarged without degrading the crosstalk properties. Simulations suggest that low cross talk and/or large A(eff) could be achieved by adjusting the trench parameters. Large mode area could be obtained by utilizing small trench (small trench width c, small refractive index difference Δ(trench)) in the trench-assisted MCF (TA-MCF), whereas low cross talk could be achieved by utilizing larger trench (large trench width c, large Δ(trench)) in the TA-MCF.