Multicore Fiber Research Articles

Photonic Temporal Operators for Microwave Signals Enabled by Multicore Fibers

Photonic Temporal Operators for Microwave Signals Enabled by Multicore Fibers

Entanglement manipulation through multicore fibres

Multicore fibres are recently gaining considerable attention in the context of quantum communication, where their capability to transmit multiple quantum states along different cores of the same channel makes them a promising candidate for the implementation of scalable quantum networks. Here, we show that multicore fibres can be effectively used not only for the scope of communication but also for the manipulation of entangled states. Exploiting the formalism of completely positive trace-preserving maps, we describe the action of a multicore fibre as a quantum channel and investigate the propagation of a transmitted state under the effect of decoherence and inter-core crosstalk. Then, we propose a novel protocol for the manipulation of the entanglement where, starting from a maximally entangled state of two qudits, we use a multicore fibre to create new families of mixed entangled states. Notably, the presence of crosstalk is fundamental for the generation of such states.

High Spectral-Efficiency, Ultra-low MIMO SDM Transmission over a Field-Deployed Multi-Core OAM Fiber

High Spectral-Efficiency, Ultra-low MIMO SDM Transmission over a Field-Deployed Multi-Core OAM Fiber

Compact Torsion Sensor With High Sensitivity Using Angle-Offset Long Period Grating Inscribed in Multicore Fiber

Compact Torsion Sensor With High Sensitivity Using Angle-Offset Long Period Grating Inscribed in Multicore Fiber

Physical coherent cancellation of optical addressing crosstalk in a trapped-ion experiment

Abstract We present an experimental investigation of coherent crosstalk cancellation methods for light delivered to a linear ion chain cryogenic quantum register. The ions are individually addressed using focused laser beams oriented perpendicular to the crystal axis, which are created by imaging each output of a multi-core photonic-crystal fibre waveguide array onto a single ion. The measured nearest-neighbor native crosstalk intensity of this device for ions spaced by 5 µm is found to be ∼ 10 − 2 . We show that we can suppress this intensity crosstalk from waveguide channel coupling and optical diffraction effects by a factor > 10 3 using cancellation light supplied to neighboring channels which destructively interferes with the crosstalk. We measure a rotation error per gate on the order of ϵ x ∼ 10 − 5 on spectator qubits, demonstrating a suppression of crosstalk error by a factor of > 10 2 . We compare the performance to composite pulse methods for crosstalk cancellation, and describe the appropriate calibration methods and procedures to mitigate phase drifts between these different optical paths, including accounting for problems arising due to pulsing of optical modulators.

Benchmarking framework for resource allocation algorithms in multicore fiber elastic optical networks

The lack of standards in the performance evaluation of new resource allocation algorithms in multicore fiber elastic optical networks (MCF-EONs) compromises the fairness when comparing them with the state of the art. This paper reviews the different transmission parameters, network parameters, performance metrics, and baselines used by the recent proposals to build a framework for future benchmarking of such algorithms according to the nature of the network operation, whether static or dynamic. This framework aims to provide standards regarding evaluation criteria, scenarios, and performance metrics, as well as recommendations concerning technology advances to promote methodology and reproducibility in further related studies.

Multicore-fiber submarine systems [Invited

This paper reviews and analyzes multicore-fiber technologies in the context of submarine networks. As global/transcontinental capacity continues to grow at a large and steady pace, the subsea industry is challenged to deliver technologies that provide large-capacity networks in a faster, greener, and cost-effective fashion. Multicore fiber has been considered as a serious candidate for next-generation systems with the ability to maintain standard cable size at large core counts. This paper analyzes the technoeconomics of next-generation submarine systems including variables such as equipment size versus marine cost and other critical elements (not analyzed before, to our knowledge) for submarine system implementation. In this context, this paper also analyzes the state-of-the-art of multicore subsystems and components and discusses their roadmaps, requirements, and evolution toward the realization of a multicore ecosystem for next-generation SDM systems.

3D shape sensor based on discrete-point Rayleigh reflectors inscribed by femtosecond pulses in multicore fibers

Fiber optic sensors which use reflectometry methods to process Rayleigh backscattering signal, are susceptible to any optical losses due to the inherently low level of Rayleigh backscattering in standard telecom optical fibers. In this work, we fabricate and study the shape sensor based on a multicore optical fiber with randomly spaced discrete-point reflectors inscribed in its cores by femtosecond laser pulses. By testing the sensor on different 3D shape samples, we demonstrate the robustness of the shape reconstruction accuracy to introduced optical losses of the signal up to 20 dB with the relative reconstruction error being less than 4 %. In contrast, such level of optical losses dramatically increases the reconstruction error when the unmodified fiber cores are used. A higher signal-to-noise ratio together with low birefringence of the inscribed point reflectors enable accurate shape sensing including the forms with low curvature.

High-resolution mid-infrared image transport by a chalcogenide multi-core fiber

Abstract We have successfully demonstrated high-resolution mid-infrared image transport by a multi-core fiber made of chalcogenide glasses.
The fiber cores are arranged on a triangular lattice, and adjacent cores have different core diameters to reduce cross-talk between them.
We tested the resolution of the fiber using different fineness patterns and found that it can resolve better than 25 lp/mm at a wavelength of 9.3 μm.
This demonstrates the potential of the fiber for high-resolution thermal imaging inside the human body.

Multicore fiber design housing a fluorine-doped low-latency core and cutoff shifted cores

Design of heterogeneous 4-core fiber housing a low-latency core and conventional cutoff shifted cores in a standard 125-μm cladding diameter is investigated to enable signal processing delay reduction using common mode impairment. For the low-latency core, 1-μs propagation delay reduction and an optical signal-to-noise ratio (OSNR) comparable to or greater than that of cutoff shifted cores are required. In this paper, we consider an F-doped core and depressed cladding structure with a large effective area as the low-latency core. It can be expected to achieve sufficient group delay reduction of the low-latency core, the OSNR unification among heterogeneous cores, and low inter-core crosstalk in a standard 125-μm cladding diameter. Consequently, we revealed the optimized low-latency core achieving the group delay reduction of 1 μs and the OSNR as same level as the cutoff shifted cores as we expected. The designed heterogeneous 4-core fiber with the standard 125-μm cladding diameter suppressed the inter-core crosstalk to be low enough to support a 1,000-km long transmission. We expect the figure-of-merit (FoM) of the 4-core fiber to be as high as previously reported 4-core fibers, and the FoM improvement are found when the low latency core and cutoff shifted core are placed alternately thanks to the core heterogeneity.

Single-End-Access BOCDA Enabled by Multi-Core Fiber for Dynamic Strain Measurements

Single-End-Access BOCDA Enabled by Multi-Core Fiber for Dynamic Strain Measurements

A RMSCA algorithm for space division multiplexing elastic optical networks with core switching

Space division multiplexing elastic optical networks (SDM-EONs) have attracted much attention due to the advantages of high capacity, flexibility, and spectrum utilization. Space division multiplexing technology enhances the capacity of a single fiber link by using multi-core fiber (MCF). With the support of MCFs, SDM-EONs will become an important form of future optical transmission networks.In order to reduce the blocking rate of the network, this paper proposes a routing, modulation format, spectrum and core allocation (RMSCA) algorithm based on the maximum number of available cores with core switching. The algorithm selects the spectrum block with the most available cores in the entire path for spectrum allocation by using core switching. We perform simulations on two networks, NSF-Net and UBN24, and compare them with the spectrum allocation algorithm with core switching (FF-ISC-RMSCA), which uses first-time adaptation, and the spectrum allocation algorithm with maximum number of cores available (N-ISC-RMSCA), which does not perform core switching. Simulation results show that the proposed algorithm significantly reduces the bandwidth blocking rate and has high spectrum utilization.

A Numerical Assessment of the Effect of Concatenating Arbitrary Uncoupled Multicore Fiber Segments on Intercore Crosstalk in Long-Haul Communication Links

Random core dependent loss (CDL) has been shown to increase the direct average intercore crosstalk (ICXT) power in long-haul uncoupled multicore fiber (MCF) links. Longer links are composed of multiple MCF segments, and random CDL may arise on these links from manufacturing imperfections. During link implementation, other random effects may arise and enhance the ICXT power. In this work, the effect of concatenating MCF segments with random characteristics on the direct average ICXT power in long-haul links is assessed numerically by studying the influence of the randomness of segment length, coupling coefficient, and random CDL on the mean, standard deviation, relative spread, and excess kurtosis of the ICXT power. The numerical results show that the segment length randomness marginally affects the ICXT power. For 2000 km long links and a 6 dB maximum random variation of the coupling coefficients, the mean almost doubles and the standard deviation almost triples, relative to considering only random CDL. However, the effect of the coupling coefficients randomness on the relative spread and excess kurtosis is reduced, not affecting significantly the nearly Gaussian distribution of the direct average ICXT power and the excess of direct average ICXT power (less than a 0.26 dB increase relative to considering only random CDL).

Realization of triple dispersion turning points in tapered seven-core fiber interferometer for sensitivity enhancement

Seven-core fibers have been widely applied in optical network, astronomy, and sensing applications. In this work, we report and demonstrate the existence of triple dispersion turning points of the super-mode interferences in a seven-core fiber spliced between two single-mode fibers by modifying the diameter of the multi-core fiber. The sensitivities of the interferometer on external variables, i.e., temperature, axial strain, and refractive index (RI), are measured, showing significant enhancement around the dispersion turning points. Compared to the regular multi-core fiber device without dimension modification, the sensitivities of temperature and axial strain are improved by about 60 times and 73 times around the dispersion turning points, respectively. While the regular device has no response to the external refractive index, the magnitude of RI sensitivity can reach as high as 33 459.0 nm/RIU in air, when the fiber diameter is modified to approach the dispersion turning point, enabling the discrimination of the refractive indices of N2 and CO2. The modification method of locating the modes at the dispersion turning points significantly enhances device sensitivity, providing an avenue for integrating ultra-sensitive sensors into commercial fiber networks.

Inter-Mode Crosstalk Estimation between Cores for LPmn Modes in Weakly Coupled Few-Mode Multicore Fiber with Perturbations.

A novel inter-mode crosstalk (IMXT) model of LPmn mode for weakly coupled few-mode multicore fiber is proposed based on the coupled mode theory (CMT) with bending and twisting perturbations. A universal expression of the mode coupling coefficient (MCC) between LPmn modes is derived. By employing this MCC, the universal semi-analytical model (USAM) of inter-core crosstalk (ICXT) can be applied to calculate the IMXT. Simulation results show that our model is generally consistent with previous theories when stochastic perturbations are absent. Moreover, our model can work effectively when stochastic perturbations are present, where former theories are not able to work properly. It has been theoretically found that the MCC has an intimate relationship with core pitch. Our model, based on the CMT, can provide physical characteristics in detail, which has not been reported clearly by former theories. In addition, our model is applicable to phase-matching and non-phase-matching regions of both real homogeneous and heterogeneous few-mode multicore fibers (FM-MCFs) with a wider range of applications.

Reducing capillary depth fluctuations in high-speed laser welding of stainless steel using multi-core laser technology

Laser welding was carried out in AISI304 (X5CrNi18-10) stainless steel using a multi-core fiber laser. High-speed X-ray imaging was used to monitor the process. When employing core-power only (400W) at high welding speeds (12m/min), the capillary depth was found to be inconsistent. The capillary penetration into the material varied from approximately 0.8 mm to approximately 0.2 mm, with fluctuation periods of between single milliseconds and tens of milliseconds. Employing a 0.5:0.5 ring-core power distribution (390W:390W) to achieve the same penetration (0.8mm) was found to reduce fluctuations in the depth of the welding process and the capillary penetration. Possible reasons for this reduction in depth fluctuations are discussed together with a detailed description of the resulting changes in weld cross-section.

Observation of tapered multicore fibers based on Nb2CTx for humidity sensing: Experiment and DFT simulation investigations

Recent advancements in the area of human healthcare monitoring and medical diagnosis have sparked a revived interest in humidity sensors. Nb2CTx, characterized by its multilayered structure, large specific surface area, and plentiful hydrophilic groups, actively absorbs a sufficient quantity of water molecules. In this work, the sensing capability and mechanism of water molecules are investigated under different proportions of functional group distribution on the surface of Nb2CTx MXene employing plane-wave based density functional theory calculations, and the provided models can offer guiding principles for the experimental preparation of the highly sensitive humidity sensor based on Nb2CTx. To verify the effectiveness of the model, Nb2CTx material is coated on a Tapered Three-Core Fiber (TTCF), and the high evanescent field characteristics of the sensor are utilized to further improve its performance. As the relative humidity (RH) increased from 35 % to 75 %, the transmitted spectra exhibited a redshift with a sensitivity of 22pm/% RH. Within the relative humidity range of 75 % to 95 %, the Nb2CTx coating heightened water molecule absorption, resulting in a more pronounced redshift in the transmitted spectra. This phase manifests a maximum humidity sensitivity of 299pm/% RH. Noteworthy advantages of this sensor include its uncomplicated structure, cost-effectiveness, and robust stability, rendering it highly suitable a wide variety of potential applications in fields such as biology, chemical and health processing.

Design and characteristic analysis of micro multi-core fiber vibration sensor

We proposed and fabricated a miniaturized multi-core fiber grating vibration sensor. The size of the miniaturized vibration sensor is 10mm × 10mm × 10 mm with a mass of only 0.25g. Finite element analysis and experimental tests were carried out to validate the performance of the vibration sensor. The experiment results indicate that the sensor has a sensitivity of 68.72 pm/g in the X direction and 64.52 pm/g in the Y direction within the operating frequency range of 20–240Hz. The cross-interference between the two directions of vibration measurement falls within 4 %. The sensor is suitable for measuring mechanical vibrations in the mid-low frequency range, especially in cases where size, quality, and distributed measurement are of particular concern.

Impact analysis of core layout and crosstalk on the coexistence of quantum key distribution and classical communications in heterogeneous multicore fiber

Heterogeneous multicore fibers (Hetero-MCFs) offer relatively lower inter-core crosstalk (XT) and improved bend resistance, making them feasible for the coexistence of quantum key distribution (QKD) and classical communications. However, detailed analyses of their impact on QKD performance remain limited. This study comprehensively investigates the significant effects of core layouts and XT on QKD performance in Hetero-MCFs under varying QKD service demands in theory. When allocating classical and quantum cores based on the maximum XT levels, hexagonal Hetero-MCFs perform the worst under low QKD service demand (LD), but comparably and superior to circular layouts under high QKD service demand (HD). The challenge of determining optimal parameters for the central core in hexagonal Hetero-MCFs critically influences overall QKD performance in both HD and LD scenarios. To address this, we propose a novel trench-assisted Hetero-MCF structure featuring an interleaved hexagonal core layout. This structure achieves at least 29-fold improvement in transmission distance for LD and 32-fold for HD scenarios compared to the benchmark, by utilizing two types of heterogeneous cores and providing greater flexibility. Our results also show that deploying homogeneous cores as quantum channels in Hetero-MCFs enhances QKD performance. Even with strict fabrication tolerances, the proposed structure maintains stable QKD performance with a maximum fluctuation of only 12%. These innovations provide valuable insights for analyzing the performance of Hetero-MCFs under varying QKD demands and further developing their co-fiber transmission applications.

Laser Doppler velocimetry based on multi-core fiber

Fiber laser doppler velocimetry has the advantages of high measurement accuracy, wide measurement range and non-contact measurement. Usually, fiber optic bundles are used in traditional measurement systems. Multi-core fiber (MCF) is a new structure of optical fiber with multiple cores in the same cladding and a uniform core layout. Compared to traditional fiber bundles, multi-core fibers have advantages in integration and volume. Therefore, by taking advantage of the special spatial arrangement of cores and compact structure of MCF, we investigate the laser doppler velocimetry system. The main work includes:1. Simulation and analysis of double-beam interference fringes based on MCF; 2. Construct a laser doppler velocimetry system based on MCF, and verify the feasibility of the experimental system. Our method provides an effective solution for fiber laser doppler velocimetry.