Abstract
Data rates in optical fiber networks have increased exponentially over the past decades and core-networks are expected to operate in the peta-bit-per-second regime by 2030. As current ...single-mode fiber-based transmission systems are reaching their capacity limits, space-division multiplexing has been investigated as a means to increase the per-fiber capacity. Of all space-division multiplexing fibers proposed to date, multi-mode fibers have the highest spatial channel density, as signals traveling in orthogonal fiber modes share the same fiber-core. By combining a high mode-count multi-mode fiber with wideband wavelength-division multiplexing, we report a peta-bit-per-second class transmission demonstration in multi-mode fibers. This was enabled by combining three key technologies: a wideband optical comb-based transmitter to generate highly spectral efficient 64-quadrature-amplitude modulated signals between 1528 nm and 1610 nm wavelength, a broadband mode-multiplexer, based on multi-plane light conversion, and a 15-mode multi-mode fiber with optimized transmission characteristics for wideband operation.
Swift and dynamic reconfigurability of network topology, even at the optical layer, is essential for satisfying the various requirements of future networks in diverse areas (e.g., data centers, ...5G/Beyond-5G/Local-5G/6G, factory-related networks, and telecom networks) and for addressing issues arising during a disaster. Because of recent efforts to disaggregate optical transport networks, various compact disaggregate blades (e.g., wavelength selective switches and optical amplifier blades) have become commercially available. In principle, such disaggregation technology enables network operators to optimize their networks precisely at the blade level according to their distinctive needs, although the management complexity can increase with the number and diversity of the managed equipment. This paper presents transformation algorithms for mapping between a reconfigurable optical add/drop multiplexer (ROADM)-based model and a disaggregate-blade-based model to realize a flexible and agile optical physical layer based on disaggregation technology without increasing control plane complexity. In this study, a disaggregate-blade-based model named functional block-based disaggregation (FBD) is used, in which the switching functionalities of individual optical components are defined by the integer linear programming (ILP) method using machine-readable GNU MathProg modeling language. By computing the ILP formula, the switching functionalities of whole nodes/networks can be analyzed; that is, the FBD model can form the ROADM-level nodal model by aggregating the individual blade models. With the developed transformation algorithms, automated network operations, including optical path establishment/removal and node structure updates, are experimentally demonstrated on a field testbed. After physically plugging in the new components, the node structure update including the logical topology information is automatically recognized within 5 min. Multi-domain cooperative optical path recovery triggered by the update is also performed.
We demonstrate the first continuous variable quantum key distribution (CV-QKD) system with fully digital phase and polarization tracking, enabling the first wavelength division multiplexing ...experiment for CV-QKD. We transmit 194 × 0.5 GHz channels with 25 GHz channel spacing, demonstrating an aggregate estimated asymptotic secret key rate of 172.6 Mbit/s over 25 km.
Few-mode fibers and coupled-core multi-core fibers are attractive transmission media for space-division multiplexed transmission systems as they enable a high spatial channel multiplicity whilst ...sustaining the current standard cladding diameter. This paper compares space-division multiplexed recirculating loop transmission using either a 3-mode few-mode fiber or a 3-core coupled-core multi-core fiber. After analyzing the spectral attenuation properties of both fibers, we investigate the wavelength and transmission distance dependence of the transmission channel characteristics. We find that the channel memory length is shorter and mode-dependent loss is lower in the coupled-core multi-core fiber, which can be attributed to the fundamental mode-structure differences between the two fiber types. This leads to a higher data rate at similar transmission distance for the coupled-core multi-core fiber.
Space division multiplexing (SDM) is mainly seen as a means to increase data throughput and handle exponential traffic growth in future optical networks. But its role is certainly more diverse. ...Research on SDM encourages device integration, brings newfunctionality to network elements, and helps optical networks to evolve. As a result, the number of individual components in future networks will decrease, which in turn will improve overall network reliability and reduce power consumption as well as operational expenditure. After reviewing the state-of-the-art in SDMfiber research and development with a particular focus on weakly coupled single-mode multi-core fibers, we take a look beyond the capabilities of SDM as a means of boosting transmission capacity and discuss ideas and concepts on howto exploit the spatial dimension for improved efficiency and resource sharing in optical networks.
We demonstrated simultaneous usage of 228 spatial channels (effectively) within a strand of fiber. We fabricated a 13-km 39-core 3-mode fiber and constructed a bi-directional space division ...multiplexing (SDM) transmission setup by using cascaded spatial multiplexers on both fiber ends. Aggregated intercore crosstalk and return loss of the system were below -35 and above 31 dB, respectively, over the C and L bands. The feasibility of using bi-directional SDM transmission was investigated using 10 GBaud, 37.38-Gb/s dual-polarization QPSK signals at 1550 nm and coherent detection with a 6 × 6 multi-input-multi-output equalizer. Excellent transmission properties were obtained for most spatial channels.
This paper discusses spatially diverse optical vector network analysis for space division multiplexing (SDM) component and system characterization, which is becoming essential as SDM is widely ...considered to increase the capacity of optical communication systems. Characterization of a 108-channel photonic lantern spatial multiplexer, coupled to a 36-core 3-mode fiber, is experimentally demonstrated, extracting the full impulse response and complex transfer function matrices as well as insertion loss (IL) and mode-dependent loss (MDL) data. Moreover, the mode-mixing behavior of fiber splices in the few-mode multi-core fiber and their impact on system IL and MDL are analyzed, finding splices to cause significant mode-mixing and to be non-negligible in system capacity analysis.
We present an experimental investigation of the Q -factor penalty due to intra and intermodal nonlinear signal distortions on 24.5 GBaud 16-quadratic-amplitude modulation based spatial super channel ...in a 36 km few-mode fiber. The results show that intermodal nonlinear signal degradations, caused by interfering spectral components separated by more than 17 nm, lead to similar Q -factor penalties as intramodal nonlinear signal degradations, originating in spectral components of less than 1 nm separation. We further compare the experimentally observed intra and intermodal nonlinear signal degradations with an analytical nonlinear Gaussian noise model and find a strong agreement between the two, validating the model as a computationally inexpensive tool for the design of few-mode fiber-based transmission systems.
We investigate a high-capacity, space-division-multiplexed (SDM) transmission system using self-homodyne detection (SHD) in multi-core fiber (MCF). We first investigate SHD phase noise cancellation ...with both kHz and MHz range linewidths for both quadrature-phase shift-keyed (QPSK) and 16 quadrature-amplitude modulation (16QAM) signals, finding that phase noise cancellation in SHD enabled transmission with MHz linewidth lasers that resulted in error floors when using intradyne detection. We then demonstrate a high throughput SHD transmission system using low-cost, MHz linewidth distributed feedback lasers. We transmit a CW pilot-tone on a single core of a 10.1 km MCF span with the remaining 18 cores used to transmit 125 wavelength-division multiplexed (WDM) QPSK and polarization-division-multiplexed (PDM)-QPSK signals with 50 GHz channel spacing at 25 GBd. For PDM transmission and assuming a 7% forward-error correction overhead this is equivalent 210 Tb/s transmission with a SE of 33.4 b/s/Hz. High-capacity transmission is achieved despite high inter-core crosstalk, broad transmitter linewidth and narrow channel spacing, showing that combining SHD with MCF enables high throughput, low-cost transmission in next-generation optical networks.
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