Search Results (4)

The growing demand for high-fidelity, multi-parameter, distributed sensing in critical domains such as structural health monitoring, oil and gas exploration, and secure perimeter surveillance is pushing traditional optical fiber sensors (OFS) to their performance limits. Although conventional multiplexing techniques such as time-division and wavelength-division multiplexing (TDM, WDM) have been commercially successful, they are rapidly approaching fundamental bottlenecks in sensor density, spatial resolution, and data capacity. This review argues that the synergistic convergence of space-division multiplexing (SDM) and artificial intelligence (AI) represents a paradigm shift, enabling a new generation of intelligent, high-dimensional sensing networks. We comprehensively survey the state of the art in SDM-based OFS, detailing the operating principles and applications of multi-core fibers (MCFs) for ultra-dense sensor arrays and 3D shape sensing, as well as few-mode fibers (FMFs) for mode-division multiplexing and enhanced multi-parameter discrimination. However, the unprecedented spatial parallelism provided by SDM introduces significant challenges, including inter-channel crosstalk, complex signal demultiplexing, and massive data volumes. This paper systematically explores how AI, particularly machine learning (ML) and deep learning (DL), is being leveraged not merely as a tool but as an indispensable core technology to mitigate these impairments. We critically analyze AI’s role in digital crosstalk suppression, intelligent mode demultiplexing, signal denoising, and solving complex inverse problems for parameter estimation. Furthermore, we highlight how this AI–SDM synergy enables capabilities beyond the reach of either technology alone, such as super-resolution sensing and predictive analytics. The discussion is extended to include the critical supporting pillars of this ecosystem, such as advanced interrogation techniques and the associated data management challenges. Finally, we provide a forward-looking perspective on the trajectory of the field, outlining a path toward cognitive sensing networks that are self-calibrating, adaptive, and capable of autonomous decision-making. This review is intended to serve as a foundational reference for researchers and engineers at the intersection of photonics and intelligent systems, illuminating the pathway toward tomorrow’s intelligent sensing infrastructure. Full article

A multiplexing method for orbital angular momentum (OAM) beams was proposed. The aperture size as a new information carrier was provided, and it could be modulated by the external variable aperture. The field of the beams propagating through turbulence was derived and discretized with Gauss–Legendre quadrature formulas. Based on this, the demultiplexing method was improved, and the beam OAM states, amplitude, Gaussian spot radius and aperture radius were decoded. Moreover, the influence of turbulence on the multiplexing parameters was also analyzed, and the decoding precision of the aperture radius was higher than that of other parameters. The aperture radius was recommended as an extra carrier for multiplexing communication. This study provides a simple method to modulate the information carried by OAM beams, and it has promising applications in large capacity laser communication. Full article

Many modern and future systems, based on the wireless communication at the THz frequencies, could benefit from multichannel transmission. One of the possible approaches is to (de)multiplex several separate signals to and from a single transmission channel using dedicated diffractive optical elements. Proper selection of receivers for such systems is crucial and strongly depends not only on the frequencies used but also on the geometry of the setup. In this article, we present a complex analysis of the applicability of various detectors for the characterization of highly convergent and off-axis beams. Three three-focal-spot diffractive lenses have been designed, optimized and manufactured to verify the influence of parameters such as focal length, focal position shift, deflection angle or radiation frequency on the proper detection and separation of focal spots using different receivers. The reliable characterization of multi-focal-point structures can be performed only with high-acceptance-angle detectors, such as, for example, field-effect transistors equipped with a patch antenna. On the other hand, for the detection of a single demultiplexed signal, a much more directive receiver can be applied, as long as it is placed at a proper angle. Full article

A four green transverse magnetic (TM)/red transverse electric (TE) light wavelength demultiplexer device, based on multi slot-waveguide (SW) structures is demonstrated. The device aims to demultiplex wavelengths in the green/red light range with wavelengths of 530, 540, 550, and 560 nm; 630, 640, 650, and 660 nm. This means that the device functions as a 1 × 4 demultiplexer for each polarization mode (TE/TM). The controlling of the light switching between two closer segment SWs under the TM/TE polarization mode was studied by designing a suitable SW structure and setting the right segment length to fit the coupling lengths of the operating wavelengths. The device is composed of six-segment SW units and six S-bends (SB) SW. The key SW and SB parameters were optimized and determined by a full vectorial beam propagation method (FV-BPM). Results show power losses better than 0.138 dB, crosstalk better than −21.14 dB, and an optical spectrum smaller than 9.39 nm, with an overall compact size of 104.5 µm. The device can be integrated in wavelength division multiplexing (WDM) for increasing data bit rate in a visible light communication (VLC) system. Full article