This paper investigates network performance with pure fiber switching, exploring tighter channel spacings unconstrained by wavelength-routing granularity. It evaluates adjacent crosstalk and nonlinear transmission penalties using 800ZR+ coherent pluggable interfaces with two core topologies. © 2026 The Author(s)

We demonstrate OESCL-band same-wavelength bi-directional transmission over 60 km HCF with 42.5 THz bandwidth, achieving GMIs comparable with the highest unidirectional SMF data-rates in both directions, with an aggregate of 423.7 + 426.5 Tb/s.

We demonstrate continuous distributed acoustic sensing over a 4400km long undersea cable. Bi-directional operation improves the strain signal-to-noise rate by >20dB, enabling 88000 50-m-spaced measurement points at a nominal telecom launch power.

We propose using large language models (LLMs) to optimize fiber design simulations and enhance automation. Our results demonstrate that LLMs can efficiently design multimode fibers with reduced mode coupling between mode groups.

We demonstrate real-time 10-mode transmission over 48-km graded-index multi-mode fiber. The MIMO receiver is implemented using twenty heterodyne receivers, three FPGAs and a GPU processing server, supporting flexible reconfiguration of the receiver DSP.(c) 2024 The Author(s)

We detect the recent M8.8 mega-earthquake in Eastern Russia, on a 4400km long active telecom cable in the Pacific Ocean. The resolution achieved 100m represents the highest spatial resolution, the largest number of ocean-bottom sensors, and the first fiber-optic deep-ocean observation of a tsunami wave.

The rapid evolution of AI, cloud, and connectivity demands higher capacity, lower latency, and more flexible networks. Optical networking provides the foundation for this future, connecting compute platforms and users. This paper explores the challenges and opportunities of building future scalable optical network.

Spatiotemporal toroidal orbital angular momentum (OAM) beams are a developing class of spatiotemporal beams which have key applications within quantum physics, metrology, imaging and optical manipulation. However, the full realization of these applications require complete configurability within tunable temporal duration, 3D geometric structure and OAM charge of these beams along with amplitude, phase and polarization control. In this paper, we demonstrate complete configurability of programmable, polarization-resolved OAM toroidal beams after propagation through a multimode optical fiber (MMF) supporting 90 spatial/polarization modes. We show high fidelity control: temporally with beams spanning 2.3 ps - 6.8 ps, geometrically with toroidal aspect ratios spanning 1.5-2.7 and with up to $|l|=13$ OAM topological charge. In total this system supports 25,000 spatiotemporal and polarization degrees of freedom which enables the independent control of all physical and geometric properties of these 3D toroidal beams. By utilizing an MMF, this system also enables toroidal beam delivery to previously inaccessible regions, paving the way for applications including optical manipulations, sensing and imaging through complex photonics media such as scattering biological tissues.

We demonstrate first simultaneous bidirectional operation of coherent point-to-point overlay over PON ODN delivering 400G at 29-dB and 200G/100G at > 35-dB optical budget using off-the-shelf pluggable single-laser single-carrier coherent transceivers. We propose to use duplex feeder to overcome limitations due to distributed Rayleigh backscatter. (c) 2025 The Author(s)

Optical toroidal beams, with donut-shaped intensity profiles and orbital angular momentum (OAM), are promising for applications such as optical manipulation, metrology, and advanced light-matter interactions. However, practical implementations are limited by challenges in controlling their full 3D geometry and the orientation of their OAM. In this paper, we experimentally demonstrate high-dimensional, polarization-resolved, programmable 3D spatiotemporal toroidal beams with arbitrary 3D geometry. The beams are delivered after propagation through an optical multimode fiber (MMF) that supports 90 spatial/polarization modes. However, if desired, this system can also deliver these beams directly into free space as well. Our approach leverages 25,000 programmable spatiotemporal and polarization degrees of freedom to achieve precise manipulation of the amplitude, phase, polarization and temporal properties of toroidal beams. These beams feature highly customizable 3D geometries, allowing independent control of their aspect ratio and orientation. We further demonstrate the generation of beams with arbitrary OAM orientation, with beam rotations about any 3D spatiotemporal axis. These beams are delivered through an MMF which enables their transport deep into scattering materials and into otherwise hard-to-access regions which could include biological tissues. Hence, this device could enable the application of completely customizable optical manipulations, including rotations, deep within these materials.

We combine 6 doped-fiber amplifiers (O-(x2), E-, S-, C-, L-bands) with discrete Raman U-band amplifiers and distributed Raman-amplification to transmit in each of the low-loss transmission bands of a standard optical fiber. For transmission distances up to 100 km, we explore ultra-wideband transmission of up to 1505 x 25 GHz spaced channels covering the O-, E-, S-, C-, L- and U-bands from 1281.2 nm to 1649.9 nm. After describing the amplifier and spectrum flattening technology, we first characterize the transceiver in back-to-back configuration. Then, for 50 km transmission, we report a record aggregate transmission bandwidth of 37.6 THz with a record standard single-mode fiber transmission data-rate of 402.2 Tb/s, estimated from GMI, and 378.9 Tb/s after FEC decoding. 100 km transmission allows a 36.6 THz bandwidth with 339 Tb/s GMI estimated data-rate and 322.8 Tb/s decoded data-rate. These results show the potential of ultra-wideband transmission covering the low-loss window of silica fibers as well as the challenges of building such systems on longer fiber spans.

This study compares distinct approaches for gradual fiber activation to streamline operating expenditure as traffic grows in WDM transparent networks featuring a large bundle of fibers per link. We show how their effectiveness depends on the architecture of optical nodes. (c) 2025 The Author(s)

We investigate mode permutation in a 15-mode fiber system to mitigate modal dispersion, effectively reducing the growth of the intensity impulse response duration with transmission distance, thereby decreasing MIMO-DSP complexity.

We propose and experimentally demonstrate a cavity-assisted pump recycling scheme that significantly enhances pump utilization efficiency in cladding-pumped EDFAs. This innovative approach achieves record-setting power conversion efficiencies in both cladding-pumped 4-core and 7-core EDFAs.

We demonstrate the generation of optical toroidal beams through a multimode fiber using a polarization-resolved optical wavelength selective switch in tandem with a multiplane light conversion device, opening new perspectives for high-capacity optical communications.

High-resolution fiber sensing is demonstrated over a 6300km trans-oceanic subsea cable, overcoming prior reach limitations. This enables unprecedented deep-ocean monitoring with similar to 50m spatial resolution, revealing seismic activity, ocean dynamics, and cable coupling/burial conditions.

We evaluate the performance of LLMs in multi-agent systems for complex cross-domain network orchestration, interoperability and task automation. We demonstrate the effectiveness of this approach across IP, optical, and robotic domains.

We explore the efficacy of mode permutation to mitigate the impact of modal dispersion in a 15-mode fiber link for long-haul space-division multiplexed transmission. By introducing strong coupling between all the fiber modes, mode permutation reduces the growth rate of the link's intensity impulse response (IIR) with transmission distance, yielding a reduction in the receiver MIMO-DSP complexity. Using a recirculating fiber-loop configuration, we experimentally compare four permutation schemes and find that they are similarly effective in reducing the increase of the IIR duration from proportional to the square-root of propagation distance. At the reach of 530 km - the largest achievable with the time-domain MIMO window of 71.4 ns available in the experiment in the absence of mode permutation - the IIR duration is seen to reduce from almost 40 ns to less than 15 ns, while the maximum reach achieved with the use of mode permutation increases to 1178 km. We also devise a simple model to simulate propagation in realistic MMF links with independent fiber spans, whose parameters can be conveniently extracted from the data. In achieving good agreement between the simulated and experimental results, the model suggests that the effectiveness of mode permutation in a realistic 15-mode fiber link, composed of independent fiber spans, is only slightly greater than in the experimental recirculating-loop configuration.

We perform submarine cable environmental sensing using an FPGA+GPU-based real-time polarization-resolved coherent OFDR prototype. Measurements of earthquake waves propagating across the Atlantic Ocean are recorded simultaneously at >70 evenly distributed points along the cable.

We experimentally investigate an extended reach E, S, C + L-band transmission system covering 27 THz with mid-span doped fiber and distributed Raman amplification, measuring 264.7 Tb/s from GMI and 250.8 Tb/s after decoding after 200 km transmission.