Multicore Fiber Research Articles

Demonstration of a Three Node Wavelength Division Multiplexed Hybrid Quantum-Classical Network through Multicore Fiber

Demonstration of a Three Node Wavelength Division Multiplexed Hybrid Quantum-Classical Network through Multicore Fiber

Sub-Micron Two-Dimensional Displacement Sensor Based on a Multi-Core Fiber

A sub-micron two-dimensional displacement sensor based on a segment of multi-core fiber is presented in this paper. Light at the wavelengths of 1520 nm, 1530 nm, and 1540 nm was introduced separately into three cores of a seven-core fiber (SCF). They were independently transmitted in their respective cores, and after being emitted from the other end of the SCF, they were irradiated onto the end-face of a single-mode fiber (SMF). The SMF received light at three different wavelengths, the power of which was related to the relative position between the SCF and the SMF. When the SMF moved within a two-dimensional plane, the direction of displacement could be determined based on the changes in power at different wavelengths. As a benefit of the high sensitivity of the spectrometer, the sensor could detect displacements at the sub-micron level. When the SMF was translated in 200 nm steps over a range from 5.2 μm to 6.2 μm, the sensitivities at the wavelengths of 1520 nm, 1530 nm, and 1540 nm were 0.34 dB/μm, 0.40 dB/μm, and 0.36 dB/μm, respectively. The two-dimensional displacement sensor proposed in this paper offers the advantages of high detection precision, simple structure, and ease of implementation.

Shape measurement by using multicore optical fiber sensor with asymmetric dual cores

Abstract Shape measurement by using multicore optical fiber sensor has attracted more attention in many fields due to the good consistency of the fiber cores. Three symmetrically arranged cores in multicore fiber are usually used for reconstructing shape by calculating the bending vectors, which will not be achieved when one of the cores is damaged or occupied in actual application. A shape measurement method using multicore optical fiber sensor with asymmetric dual cores is proposed in this paper. Based on analyzing the principle of shape reconstruction and the geometric relationship of asymmetric dual cores in multicore fiber sensor, the bending vector is decomposed. The mathematical expressions for bending curvature and orientation of asymmetric dual cores are derived. The two dimensional (2D) and three dimensional (3D) shape reconstruction results both in finite element modelling simulation and shape measurement experiment based on optical frequency domain reflectometry have shown that the proposed method using multicore fiber sensor with asymmetric dual cores is able to achieve shape measurement, and its performance is comparable and even equivalent to the traditional method by using three symmetrically arranged cores. In the experiment, the maximum relative errors of 2D and 3D reconstructed shapes are 2.653% and 5.139%, respectively. The proposed method, which only needs asymmetric dual cores in the multicore optical fiber sensor for shape reconstruction, will be conducive to solve the limitation of multicore optical fiber sensors in shape measurement applications.

Femtosecond Laser Direct-writing Tilted Fiber Bragg Gratings in Multi-core Fiber

Femtosecond Laser Direct-writing Tilted Fiber Bragg Gratings in Multi-core Fiber

Ultra-high-capacity band and space division multiplexing backbone EONs: multi-core versus multi-fiber

Both multi-band and space division multiplexing (SDM) independently represent cost-effective approaches for next-generation optical backbone networks, particularly as data exchange between core data centers reaches the petabit-per-second scale. This paper focuses on different strategies for implementing band and SDM elastic optical network (BSDM EON) technology and analyzes the total network capacity of three sizes of backbone metro-core networks: ultra-long-, long-, and medium-distance networks related to the United States, Japan, and Spain, respectively. Two BSDM strategies are considered, namely, multi-core fibers (MCFs) and BSDM based on standard single-mode fiber (SSMF) bundles of multi-fiber pairs (BuMFPs). For MCF-based BSDM, we evaluated the performance of four manufactured trench-assisted weakly coupled (TAWC) MCFs with 4, 7, 13, and 19 cores. Simulation results reveal that, in the regime of ultra-low (UL) loss and inter-core crosstalk (ICXT), MCF-based throughput can be up to 14% higher than SSMF BuMFP-based BSDM when the core pitch exceeds 43 µm and the loss coefficient is lower than that of standard single-mode fibers. However, increasing the number of cores with (non-)standard cladding diameters, UL loss, and ICXT coefficient is not beneficial. As core counts increase up to 13 for non-standard cladding diameters (<230µm), the core pitch and loss coefficient also increase, leading to degraded performance of MCF-based BSDM compared to SSMF BuMFP-based BSDM. The results indicate that, in scenarios with 19 MFPs, SSFM BuMFP-based BSDM outperforms 19-core MCF-based scenarios, increasing the throughput by 55% to 73%, from medium-backbone networks to ultra-long ones.

Short range optical communication with GaN‐on‐Si microLED and microPD matrices

Abstract(In)GaN microLEDs have reached a high degree of maturity due to their development in the lighting industry. Their robustness and high efficiency make them ideal candidates for high‐brightness, high‐resolution micro‐displays. Beyond display applications, microLEDs are being explored for non‐display uses, including wireless Visible Light Communication (VLC) and parallel communication via multicore fiber. This study investigates short‐range chip‐to‐chip optical communication using InGaN/GaN microLEDs and micro Photodiodes (microPDs). Leveraging processes developed for micro‐displays, we address the challenges of integrating GaN microLEDs and microPDs on ASICs. We outline the main figures of merit, including expected energy efficiency, optical coupling to multicore fibers or waveguides, and the spectral efficiency of InGaN/GaN microPDs correlated with TCAD simulation and experimental transmission results. Our study highlights the potential of GaN microLEDs and microPDs for massively parallel, energy‐efficient data transmission, paving the way for innovative short‐range and energy‐efficient optical communication solutions.

1.06 Tbit/s space division multiplexing self-homodyne coherent transmission with high spectral efficiency probabilistic shaping multidimensional modulation

We propose a probabilistic shaping multidimensional (MD) modulation format for self-homodyne coherent transmission systems. The redundancy of the MD signal is separated and transmitted together with the optical pilot tone (PT). The 4D/8D/12D modulation is constructed at the transmitter based on the amplitude translation (AT)-set partitioning (SP) principle and the probabilistic amplitude shaping (PAS) structure. Moreover, the hard-decision (HD) and soft-decision (SD) decoders for MD signals are introduced. We implement 20 GBaud 4D/8D/12D probabilistic shaping (PS) 16384-level quadrature amplitude modulation (QAM) transmission over 22.5 km uncoupled multicore fiber to analyze the performance. The experimental results show that it is possible for the MD signal to provide spectral efficiency (SE) gain up to 3.31 bit/s/Hz/4D-sym. The maximum SE transmitted is up to 57.29 bit/s/Hz, i.e., 17.5 bit/s/Hz/4D-sym, with a bit rate of 1.06 Tbit/s.

Polarity management of multicore fiber-based optical devices in unidirectional and bidirectional spatial channel networks

Uncoupled multicore fibers (MCFs) are expected to be the first to be commercially deployed due to their high compatibility with existing single-mode fiber technologies. Since MCFs have a 3D shape, they generally exhibit connection polarity. Thus, optical devices based on MCFs also generally have polarity, which will complicate the core resource assignment and end-to-end core connections in future MCF-based spatial channel networks (SCNs). In this paper, we first discuss the polarity of MCF-based optical devices (MODs) such as MCF patch cords, spatial multiplexers (SMUXs), core selective switches (CSSs), and core selectors (CSs). We then propose a definition for global core numbers in a two-MCF unidirectional (2MCF-UD) SCN and a single-MCF bidirectional (1MCF-BD) SCN. We also propose a method for managing the polarity of MODs and correctly connecting cores end-to-end. To verify the effectiveness of the proposed global core numbering and polarity management method for MODs, testbeds emulating a 2MCF-UD SCN and a 1MCF-BD SCN are constructed using prototype CSS, CS, and SMUX devices. By using light with different optical frequencies as input and observing the output spectrum, we confirm that the spatial channel specified by the global core number is established correctly end-to-end in the SCN if the polarity of the MODs is set correctly.

Photonic Temporal Operators for Microwave Signals Enabled by Multicore Fibers

Photonic Temporal Operators for Microwave Signals Enabled by Multicore Fibers

Layout design of densest weakly coupled multi-core fibers to minimize the network blocking rate

The suppression of inter-core crosstalk (IC-XT) that affects each lightpath is crucial for resource allocation in space-division multiplexing elastic optical networks (SDM-EONs) with multi-core fibers (MCFs). Resource allocation approaches that limit the simultaneous use of adjacent cores in the same frequency band to the MCFs composing each lightpath have been widely adopted to suppress IC-XT. However, in principle, such methods are inefficient because they cannot fully utilize all cores. This study examines the core density from the perspective of the core layout in weakly coupled MCFs and the IC-XT suppression requirement. The densest MCF layout maximizes the network capacity while restricting the amount of IC-XT within the tolerance threshold for each lightpath. Specifically, we propose an XT-free condition, maintaining the IC-XT to each lightpath within the acceptable tolerance level. In addition, we evaluated numerous MCFs that satisfy or do not satisfy the XT-free condition with various network topologies and cladding diameters. This evaluation also validates the IC-XT reduction performance of the proposed framework compared with that of the conventional resource-allocation approach. Here, we incorporate our indirect IC-XT calculation method that affects lightpaths from other cores via its nearest cores, which was overlooked in the resource allocation problem. Based on these comprehensive examinations, we propose a method to determine the densest core layout for a given network topology and route and modulation format selection algorithm.

Multi-core hollow core fibre

Multi-core hollow core fibre

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.