19-core Multi-core Fiber Research Articles

Advanced optical transceiver and switching solutions for next-generation optical networks

Innovative transceiver and switching approaches should be explored with special focus on flexibility, energy efficiency, sustainability, and interoperability to be adopted on next-generation 6G optical networks driven by the diverse landscape of emerging applications and services and increasing traffic demand. In this regard, multiband (MB) and spatial division multiplexing (SDM) technologies arise as promising technologies for providing suitable network capacity scaling while fulfilling the stringent requirements of the incoming 6G era. In this paper, innovative MB over SDM (MBoSDM) switching node and sliceable bandwidth/bit rate variable transceiver (S-BVT) architectures with enhanced capabilities and features are proposed and experimentally validated. Different network scenarios have been identified and assessed, enabling up to 180.9 Gb/s S+C+L transmission in back-to-back (B2B) configuration. A MBoSDM scenario including both transceiver and switching solutions is demonstrated, including a 19-core multi-core fiber (MCF) of 25.4 km. Thanks to the transceiver modular and scalable approach, higher capacities can be envisioned by enabling multiple slices working in the different bands beyond the C-band. A power efficiency analysis of the proposed transceiver is also presented, including a pathway towards the integration with a software defined networking (SDN) control plane assisted by energy-aware artificial intelligence (AI)/machine learning (ML) trained models.

Performance assessment of upstream and downstream losses in a passive optical network utilizing a 19-core multicore fiber

Performance assessment of upstream and downstream losses in a passive optical network utilizing a 19-core multicore fiber

Experimental Space-Division Multiplexed Polarization-Entanglement Distribution through 12 Paths of a Multicore Fiber

The development and wide application of quantum technologies highly depend on the capacity of the communication channels distributing entanglement. Space-division multiplexing (SDM) enhanced channel capacities in classical telecommunication and bears the potential to transfer the idea to quantum communication using current infrastructure. Here, we demonstrate an SDM of polarization-entangled photons over a 411m long 19-core multicore fiber distributing polarization-entangled photon pairs through up to 12 channels simultaneously. The quality of the multiplexed transfer is evidenced by high polarization visibility and CHSH Bell inequality violation for each pair of opposite cores. Our distribution scheme shows high stability over 24 hours without any active polarization stabilization and can be effortlessly adapted to a higher number of channels. This technique increases the quantum-channel capacity and allows the reliable implementation of quantum networks of multiple users based on a single entangled-photon pair source.

Compensation of inter-core skew in multi-core fibers with group velocity dispersion.

This work proposes an approach for the compensation of inter-core skew in homogeneous single-mode multi-core fiber links. We adjust the wavelengths of the transmitted spatial channels in such a way that the skew induced by group velocity counters inter-core skew. This approach is demonstrated experimentally using a 111 Gb/s spatial super channel (4 spatial channels at 27.8 Gb/s) on a 10.1 km 19-core multi-core fiber. It is shown that inter-core skew may be compensated without the need for devices such as variable optical delay lines or electronic buffers.

Programmable disaggregated multi-dimensional S-BVT as an enabler for high capacity optical metro networks

To meet the requirements of 5G high capacity optical metro networks, a programmable disaggregated multi-dimensional sliceable bandwidth/bitrate variable transceiver (S-BVT) is proposed. Specifically, transceiver multi-dimensionality is presented exploiting spatial, polarization, and spectral information as a solution to support network capacity and bandwidth scaling 5G requirements. Space division multiplexing is implemented by considering a 19-core multicore fiber enabling capacity scaling with the number of cores, whereas polarization division multiplexing is assessed enabling 50% spectral saving by considering two orthogonal polarization components. Finally, by the implementation of multi-band transmission systems, the optical bandwidth can be increased by a factor of 10, compared to a conventional C-band system. In these last two cases, the existing spectrum and network infrastructure can be reused, bringing new capabilities. In particular, in this work, multi-band transmission is assessed by exploiting the C-band and L-band. Additionally, disaggregation is also addressed at the transceiver level to enhance network flexibility, avoiding vendor lock-in while achieving efficiency and cost reduction. Disaggregation enables assembling open components, devices, and sub-systems into optical infrastructures and networks. On the other hand, the adoption of the software defined networking paradigm enables system/network programmability and reconfigurability, promoting an efficient use of the multi-dimensional network resources. Therefore, in this work, we analyze and experimentally demonstrate different S-BVT advanced functionalities suitable to support the stringent network requirements of 5G. These capabilities include rate/distance adaptability, programmability/configurability, disaggregation, and multi-dimensionality. Different network scenarios have been considered to assess the S-BVT functionalities, enabling Tb/s optical transmission.

Crosstalk-Induced System Outage in Intensity-Modulated Direct-Detection Multi-Core Fiber Transmission

Crosstalk-power in homogenous single-mode multi-core fibers can vary by more than 20 dB over time and frequency. The extend of these fluctuations depends on the interacting cores’ propagation parameters and the transmitted modulation format. Furthermore, the polarizations of signal and crosstalk can change randomly during transmission. In this paper, we describe the effect of random crosstalk-power variations and the relative signal-crosstalk polarization fluctuations when transmitting single-polarization, intensity-modulated signals such as on-off-keying. We show experimentally that the polarization of a signal fluctuates slower than the polarization of crosstalk, indicating uncorrelated processes. We further investigate the system impact of both, crosstalk-power fluctuations and the relative signal-crosstalk polarization variations on a 10 Gb/s on-off-keying transmission system employing a 10.1 km 19-core multi-core fiber. We show that the two-dimensional space of random fluctuations that is spanned by crosstalk power and relative signal-crosstalk polarization can vary the system's bit error rate by more than five orders of magnitude.

Inter-core crosstalk in weakly coupled MCFs with arbitrary core layout and the effect of bending and twisting on the coupling coefficient.

We investigate the bending and twisting-induced longitudinal variation of the inter-core coupling coefficient (ICCC) and its effect on inter-core crosstalk (ICXT) in weakly coupled multi-core fibers (MCFs) with an arbitrary core layout. An analytical discrete changes model (DCM) for ICXT field propagation under those conditions is proposed for the first time, providing very fast and rather accurate mean ICXT power estimates. The analytical mean ICXT power estimates are validated through numerical simulation. It is predicted that the mean ICXT power between adjacent cores of the outer ring of the 19-core MCF can be more than 10 dB higher than the one between adjacent cores of the inner ring. It is also predicted that the difference between the mean ICXT power of cores in the inner and outer rings can be much smaller by decreasing the core pitch and increasing the bending radius. This behavior is attributed to the ICXT dependence on the bending and twisting-induced longitudinal variation of the ICCCs. In particular, larger bending and twisting-induced fluctuations of the ICCCs along the longitudinal coordinate are observed in the cores of the outer ring, but the fluctuations become smaller for smaller core pitches and larger bending radii. Furthermore, it is shown that, if the ICCCs' longitudinal variation is neglected, the mean ICXT power estimates between two adjacent cores are very similar despite the location of those cores. This means that neglecting the longitudinal variation of the ICCCs can lead to misleading estimates of the mean ICXT power, with an error exceeding 15 dB.

Demonstration of an SDM Network Testbed for Joint Spatial Circuit and Packet Switching †

We demonstrate a spatial division multiplexing (SDM) network testbed composed of three nodes connected via 19-core multi-core fibers. Each node is capable of joint spatial circuit switching and joint packet switching to support 10 Tb/s spatial circuit super channels and 1 Tb/s line rate spatial packet super channels. The performance of the proposed hybrid network is evaluated, showing successful co-existence of both systems in the same network to provide high capacity and high granularity services. Finally, we demonstrate an optical channel selection associated with the quality of service requirements on the SDM network testbed.

Advanced and flexible multi-carrier receiver architecture for high-count multi-core fiber based space division multiplexed applications.

Space division multiplexing (SDM), incorporating multi-core fibers (MCFs), has been demonstrated for effectively maximizing the data capacity in an impending capacity crunch. To achieve high spectral-density through multi-carrier encoding while simultaneously maintaining transmission reach, benefits from inter-core crosstalk (XT) and non-linear compensation must be utilized. In this report, we propose a proof-of-concept unified receiver architecture that jointly compensates optical Kerr effects, intra- and inter-core XT in MCFs. The architecture is analysed in multi-channel 512 Gbit/s dual-carrier DP-16QAM system over 800 km 19-core MCF to validate the digital compensation of inter-core XT. Through this architecture: (a) we efficiently compensates the inter-core XT improving Q-factor by 4.82 dB and (b) achieve a momentous gain in transmission reach, increasing the maximum achievable distance from 480 km to 1208 km, via analytical analysis. Simulation results confirm that inter-core XT distortions are more relentless for cores fabricated around the central axis of cladding. Predominantly, XT induced Q-penalty can be suppressed to be less than 1 dB up-to −11.56 dB of inter-core XT over 800 km MCF, offering flexibility to fabricate dense core structures with same cladding diameter. Moreover, this report outlines the relationship between core pitch and forward-error correction (FEC).

Analytical Formulation of Supermodes in Multicore Fibers With Hexagonally Distributed Cores

The supermodes in 19-core multicore fibers (MCFs) with identical hexagonally distributed cores are analyzed in detail by using the coupled mode theory and matrix operation. The analytical formulations for both the propagation constants and modal distribution vectors of the supermodes are derived. Simulation results show that the analytical results agree well with the numerical results. In addition, the features of the effective indices and modal distributions of the supermodes are discussed by using the analytical expressions combined with the applications. The analytical expressions provide a fast and accurate method to reveal the properties and characteristics of the supermodes for MCFs and are helpful for the design and applications of MCFs.

Free-Space Coupling Optics for Multicore Fibers

In this letter, we report on coupling optics for connecting single-core single-mode fibers with multicore single-mode fibers. After a brief discussion of the options for such coupling systems, we describe our approach of using bulk optics to fabricate low-loss and low-crosstalk devices for both 7- and 19-core multicore fibers with the free-space design approach. This enables the use of the same coupling device with a variety of multicore fibers whose structural parameters differ from one sample to another. We present the results of experimental evaluations of these devices, discuss various causes of insertion loss, and analyze the coupling loss in detail.