Abstract
The demand for sixth-generation (6G) and future communication systems is pushing current wireless technologies, including the promising optical wireless communication (OWC), to their physical limits. For fundamental engineering breakthroughs, vectorial light rooted in optical physics provides a potential solution to OWC. The understanding of the physical essence of vectorial light and its use as a robust information carrier in disordered media touches upon the basic physical problem of seeking orders in disorders, thereby closely linking the future of OWC with advances in optical physics. Specifically, vectorial light fields, with different spatial modes loaded onto orthogonal polarizations, intrinsically multiplexes multiple degrees of freedom (DoFs) and enables a level of DoF control unattainable by traditional scalar modulation schemes, such as intensity modulation (IM) or homogeneous polarization modulation (PM). Furthermore, its inherent DoF coupling effect inspires novel vectorial modulation (VM) schemes, offering the possibility of a super-diversity gain. This opens up a development prospect for OWC and makes it different from conventional wireless technologies. To clarify this prospect, this article provides a systematic perspective rooted in optical physics, explaining how advances in this field are driving the evolution of scalar OWC into a vectorial era. Accordingly, we highlight the major challenges, opportunities, and preliminary solutions within this research trend. We further explore the new visions that vectorial OWC (VOWC) brings to the wireless community. For example, the multi-functional integration of optical communication, sensing, and imaging, driven by optical physics, is expected to upgrade the integrated sensing and communications functionality in 6G. Moreover, the systematic introduction of tools from cohomology theory and topological physics provides OWC with a physical perspective. We emphasize that by bridging optical physics and communication engineering, VOWC promises to greatly expand the technological vision and theoretical scope for 6G and beyond.
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Introduction
The sixth-generation (6G) and future wireless communication systems have put forward unprecedented performance requirements for potential enabling technologies, including various metrics ranging from theoretical spectral efficiency to practical data rates1,2. These technologies aim to achieve scenario expansion compared to current systems, addressing traditional challenges in areas such as mobile cellular communication3,4,5 while providing effective support for future demands like immersive communication, massive communication, and hyper-reliable and low-latency communication6. To this end, the wireless communication community is exploring the practical implementation of extremely large-scale multiple-input multiple-output (XL-MIMO)7,8,9,10,11,12,13,14 and reconfigurable intelligent surfaces (RIS)15,16,17,18,19,20,21. Concurrently, interdisciplinary innovations such as integrated artificial intelligence (AI) and communication22,23,24, semantic communication25,26,27, and integrated sensing and communications (ISAC)28,29,30 are being actively embraced. A more important goal within these trends is to expand the theoretical scope and technical routes of wireless communication itself, ensuring its core contribution to the future intelligent transformation.
Optical wireless communication (OWC), as one of the key enabling technologies for 6G31,32,33, also faces the challenge of achieving a major leap in performance. With a long history of evolution across various spectral bands, modality34,35,36,37,38,39,40,41 and application scenarios42,43,44,45,46,47,48, its current performance limits are far from theoretical expectations49, suggesting that incremental optimizations are insufficient for fundamental breakthroughs. The root cause of this issue lies in a observation that, although most OWC research centers on the concept of multiple degrees of freedom (DoFs) multiplexing36, practical implementations generally only achieve a “1 + 1 < 2” sublinear gain, rather than the ideal “1 + 1 = 2” linear gain. This predicament is analogous to the “capacity crunch” in optical fiber communications, a challenge described by the metaphor of “filling the light pipe”50. In this context, the existing “pipes”—representing conventional DoFs such as intensity and uniform polarization—are approaching their fundamental limits. Increasing the data flow through these established channels leads to diminishing returns, primarily due to physical limitations like crosstalk, resulting in a sublinear gain that we denote as “1 + 1 < 2”. This raises a fundamental question: rather than attempting to further stuff the existing pipe, can we identify and exploit entirely new dimensions within the light field itself? Vectorial light offers a compelling answer. By structuring light in all its DoFs, particularly through the coupling of spatial modes and polarization, a new and robust dimension for communication is unlocked. This new dimension, based on a physical invariant, is inherently resilient to the very perturbations that cause crosstalk in conventional systems. It offers the potential for a “super-diversity” gain in reliability, which we denote as “1 + 1 > 2”, representing a performance enhancement that surpasses the linear sum of its constituent parts.
Vectorial light fields, by loading inhomogeneous spatial modes onto different polarizations, naturally integrate the dual DoFs of inhomogeneous intensity and polarization. Given that traditional scalar modulation methods based on intensity modulation (IM) or homogeneous polarization modulation (PM) face limitations in exploiting the rich characteristics of light, the intrinsically multiplexed multi-DoF vectorial light is expected to far exceed conventional schemes. Through the transformation from one-dimensional (1D) homogeneous-field information to two-dimensional (2D) inhomogeneous-field information, and from single-DoF to multi-DoF natural coupling, vectorial OWC (VOWC) becomes the physical basis for the significant opportunities that OWC can bring to 6G communication.
Standing at the juncture where 6G is on the horizon, this Perspective advocates for a expansion of OWC’s current theoretical scope and technical routes by leveraging cutting-edge optical physics. We will first expound on the superiority of vectorial light fields as information carriers from a physics viewpoint and review the development of a core research theme: seeking and exploiting physical or statistical invariants as information carriers in disordered media. Based on this, we then highlight the broad prospects of VOWC, alongside a detailed analysis of the major challenges and potential solutions in the transition from scalar to vectorial paradigms. The logical framework guiding this perspective article is illustrated in Fig. 1. It should be emphasized that VOWC builds a crucial bridge between optical physics and communication engineering. It not only expands the connotation of 6G core functions such as ISAC by enabling the deep integration of optical communication, sensing, and imaging, but also introduces novel theoretical toolkits like cohomology and topological physics to the wireless community. Therefore, it is promising to expand the theoretical boundaries and technological landscape of the future wireless communications. Although vectorial light involves diverse physical phenomena, this Perspective will concentrate on classical entanglement as a primary mechanism to improve the robustness of OWC systems.
The diagram depicts the evolutionary path of VOWC, starting from the sublinear gain dilemma in multiplexed OWC. This challenge is addressed by leveraging physical invariants in disordered media to achieve a super-diversity gain. This leap necessitates an engineering revolution in physical modeling, channel representation, and optimization, ultimately enabling the vision for VOWC in 6G and beyond.
Background: topology and entanglement in vectorial free-space optics
This section aims to elaborate on the research progress of vectorial free-space optics (VFSO), the physical basis of VOWC, emphasizing the evolution from scalar to vectorial approaches in optical physics. Then the core objective of seeking invariants in disordered media within this paradigm is introduced and explained how it naturally positions VFSO within the research scope of robust VOWC. It is worth emphasizing that a hidden theme within this research, the active and passive manipulation of optical fields, channels, and their interactions, informs the research path of using vectorial light to counteract disordered media for information transmission. This further reveals the intrinsic logic of solving channel disorders from a perspective of physics, which holds significant inspiration for future OWC.
Specifically, this section reviews two key aspects of vectorial light relevant to OWC. We first provide a brief overview of the emerging field of topological optics, which evolved from early studies of optical orbital angular momentum (OAM). OAM describes the helical phase front of a light beam, which is characterized by a phase singularity at its core51. This spatially structured phase, arising from the angular momentum in orbital directions of photons, provides a distinct DoF for encoding information. Research trends in OAM offers a rich toolbox for the manipulation of novel optical structures in disordered media, although its application in wireless communication remains relatively unexplored. Subsequently, we delve into the concept of classical entanglement. Also originating from research in OAM, this long-standing topic forms the primary focus of this work and provides the physical basis for the proposed super-diversity gain.
Inherent multiplexing of multiple DoFs
The advent of the optical vortex52 and OAM51 mark the transition of singular optics53,54,55 from theory to the real world. Since then, a research boom spanning over three decades has commenced, focusing on spatially inhomogeneous modes56,57,58. However, the spatial mode is merely one of many DoFs of light, and light field manipulation based on a single DoF limits its application. Consequently, vectorial light59 that is generally referred to as light fields tailored by combining spatial structure with other DoFs has emerged and become more and more important. Typical vectorial lights include three types of combination, such as polarization and spatial modes, temporal and spatial modes, as well as optical path and spatial modes60. Although the latter two types can also inspire applications in OWC, a vast of research has emerged from the first type61,62. Therefore, we take the first type of vectorial light as our primary example in this article. It should be noted, however, that the latter two cases, particularly spatiotemporal OAM wave packets63,64 and optical knots65,66,67,68, may inspire VOWC application scenarios different from those envisioned here and deserve in-depth study.
In principle, higher-order couplings involving three or more DoFs can be created, such as fields with simultaneous spatio-temporal-polarization structuring. However, analogous to the exponential growth of resources required for classical systems to simulate multi-body quantum entanglement69,70, the experimental complexity of generating and detecting such higher-order coupled states increases dramatically. Consequently, this topic remains an advanced frontier of research, and this Perspective will therefore focus on the more established and experimentally accessible case of two-DoF coupling.
When different spatial light modes are loaded onto two mutually orthogonal polarization directions71, or in other words, when the polarization pattern is inhomogeneously distributed across the spatial mode72, a polarization-based vectorial light emerges. As an intrinsic extension to the single spatial mode DoF, e.g., OAM-based cases, such an operation enables a dimensional breakthrough in light field manipulation. Numerous studies have achieved certain progresses in OWC by utilizing the intrinsic dual-DoF multiplexing capability (polarization and OAM) of vectorial light fields. This marks the evolution of OWC from traditional homogeneous modulation, including IM and PM, to inhomogeneous modulation schemes, which we summarize here as vectorial modulation (VM). Along this path, as elaborated in Section “The “1 + 1 < 2” dilemma of multiplexing scalar DoFs”, a key approach is to manage the mode crosstalk of inhomogeneous spatial modes carrying information bits as they propagate through disordered media. However, such an approach does not break through the paradigm of regarding vectorial light as a natural multiplexing carrier. Consequently, a series of studies in VFSO have proposed returning to a physical question: Do invariants exist in disordered media73? Following this path, the research focuses of VFSO has begun to shift from singular structures to special particle textures74. The emergence of optical skyrmions, or more broadly, optical quasi-particle fields75, has therefore become one of the latest frontiers in VFSO.
Next, we take the optical skyrmions76 as an example to illustrate the potential of inhomogeneous modulation schemes based on vectorial light in next-generation OWC. The skyrmions, as a unified description of mesons and baryons in particle physics77, refers to as a quasi-particle with a generalized topology, whose topological property remains invariant in complex environments. Tsesses et al.78 and Du et al.79 first achieved a light field simulation of skyrmions using surface plasmons, laying the foundation for the application of skyrmionic light fields in subsequent studies. Later, Gao et al.80 and Shen et al.81,82 successfully constructed paraxial skyrmions using vectorial light fields via specific topological mapping tools, realizing special quasi-particle light structures in free space83. These paraxial optical skyrmions were later simplified and constructed using Laguerre–Gaussian and Bessel modes84,85, linked with trajectory engineering in vectorial light manipulation86, and extended to non-paraxial cases87. The stability of the topological structure of optical skyrmions in disordered media88 and the invariance of the Skyrme number attracts attention89, and have been extended to a mathematical generalization based on cohomology to address the limitations on topological number conservation under specific boundary conditions90. In a recent work91, Mata-Cervera et al. has challenged the traditional notion that generating optical topologies requires active manipulation of vectorial light fields80, revealing that the axial field components near the phase singularity of a scalar light can be naturally utilized to form an optical skyrmions structure. Optical skyrmions hold a great potential of applications, such as photonic computing92, while their use in OWC has long been predicted75. In addition to the stability of the topology itself, this structure also contributes to the stability of other physical properties of light. For instance, the non-local quantum skyrmions constructed by Ornelas et al.93 demonstrates that the topological structure within the quantum correlation of two entangled photons can enhance the resilience of quantum entanglement to noise.
The aforementioned works systematically introduce topological physics into the framework of VFSO, bringing the concepts of topological protection and stability to the field. However, these studies fall under the category of active light field manipulation. Within the realm of free-space optics, other technical routes exist, such as the active manipulation of physical or statistical quantities and passive light field manipulation based on channel priors. These seemingly parallel technical routes are all strongly related in their inherent logic to the core idea of seeking invariants in disordered media, and together they form the physical basis for future research and applications of VFSO.
Finding orders in disorders
A primary interest of optical engineering based on VFSO is how to utilize physical quantities and field structures to achieve tolerance, resistance, and even immunity to turbulence or scattering effects in free space. Currently, extensive researches exist in classical optical physics, strong scattering imaging, and turbulent channel communication, all seeking stable light field structures or physical quantities in disordered media through active or passive schemes.
Within the scope of active manipulation at the transmitter, the optical skyrmions discussed in Section “Inherent multiplexing of multiple DoFs” is a stable light field structure that is actively customized, and its topological number, as a physical quantity, is also invariant. Coincidentally, in addition to customized light field structures, some statistical or physical quantities have been found to remain constant during propagation through disturbances, directly providing usable information carriers for VOWC. These invariants, besides the topological number of optical skyrmions, also include coherence entropy94, intensity correlation95, concurrence96 and etc. These naturally stable statistical or physical quantities become the main enablers and technical advantages of VOWC over OWC. As an example, we discuss concurrence-based VOWC in Section “The “1 + 1 > 2” super-diversity in entangled VOWC”.
On the other hand, passive light field manipulation based on channel state information (CSI) or medium state information (MSI) is also feasible. Moreover, in specific circumstances, the passive modes of these channels exhibit stronger tolerance to disordered media than the aforementioned active modes, and can even achieve the immunity to channel disturbances. This research path originated from early discussions on the DoF of an image in information optics97, and was later revisited and expanded in the context of generalized wave propagation problems98,99. The core idea is that the operation of any linear medium on an input wave can be characterized by a transmission matrix, whose eigenmodes, i.e., the wave modes that can pass through with minimal energy loss, are known as high-transmitting spatial tunnels100. Inspired by this, researchers have achieved imaging through strongly scattering media, both in static101 and dynamic102 cases. Following the resemble approaches, Shatokhin et al.103 and Bachmann et al.104 have found that high-transmitting eigenmodes still exist in strong turbulence in context of OWC in turbulent channels. The use of these eigenmodes has enabled communication demonstrations with near-zero mode crosstalk by Peters et al.105 and Klug et al.106. Recent work has focused on primary challenges such as millisecond-scale online solving and feedback updating for dynamic turbulent media107,108, as well as the dimensionality-reduced representation and fast computation of large-scale transmission matrices109.
We emphasize that although this passive search for stable modes has not been explicitly associated with VOWC, that means the fields treated are typically scalar, its importance still deserves repeated emphasis for two reasons. First, this passive approach complements the previously mentioned active, VFSO-based method, jointly providing two answers to the question of seeking invariants in disordered media. Second, this passive method can be directly combined with VFSO to construct stable vectorial beam structures in disordered media, as a combined regime of active and passive light field manipulation methods.
The concept of non-separability in classical optical fields, often termed classical entanglement, was formally described as a classical analogy of entanglement69. Spreeuw69 established a theoretical framework showing that DoF within a single classical light beam, such as polarization and spatial modes, can exhibit structural inseparability analogous to quantum entanglement. Building upon this theoretical analogy, subsequent works provided experimental validation for these concepts, including violation of the Bell inequality, thereby shifting the discussion from a purely theoretical analogy to a physically measurable70. It is important to clarify the distinction between spin-orbit coupling and OAM-spin angular momentum (SAM) entanglement. Spin-orbit coupling refers to the physical interaction mechanism wherein the SAM and OAM of light can influence one another. In contrast, OAM-SAM entanglement describes the resulting state of non-separability, where the spatial and polarization DoFs of the field cannot be described independently. This Perspective aims to explores the implications of this verified non-separability110, particularly for achieving advanced OWC, with the inspiration from recent experimental successes in vectorial OWC111. We hope that the above review of the physical basis, research paths, and context of VFSO provides a physical background for the content related to VOWC in Section “VOWC: a leap from unideal multiplexing to super-diversity gain”.
VOWC: a leap from unideal multiplexing to super-diversity gain
This section starts from the popular IM and PM regimes in OWC, along with a series of examples of scalar DoF multiplexing, to explain the systematic weakness that makes it difficult to achieve the expected “1 + 1 = 2” linear gain. Subsequently, it deserves discussions that how VOWC can transcend the traditional pursuit of linear gain and directly move towards a “1 + 1 > 2” super-diversity gain, where reliability is the core metric. Guided by the physical idea of seeking invariants in disordered media as stated in Section “Background: topology and entanglement in vectorial free-space optics” and using classical entanglement as an example, we elaborate on how vectorial light fields can open up a fundamental new path for achieving ultra-robust OWC in disordered media.
The “1 + 1 < 2” dilemma of multiplexing scalar DoFs
Current research predominantly employs a single or a few DoFs of the light field for OWC system design, thereby failing to exploit the rich dimensional resources available. Existing multiple DoFs integrated OWC works have only achieved a loosely coupled effect, resulting in a “1 + 1 < 2” sublinear performance improvement. It is important to note that these works have not reached the commonly anticipated linear multiplexing gain of “1 + 1 = 2”, which corresponds to the multiplexing order gain as defined in MIMO communication theory.
In the exploration of adopting theories of singular optics in OWC, Wang et al.112 first experimentally demonstrated OAM-based OWC in free space, achieving a data rate up to 2.56 Tbps in a meter-scale channel via OAM mode-division multiplexing. This sparked a research boom in OAM communication that has lasted over a decade. Subsequent work further extended this achievement to a 143 km turbulent atmospheric link113 and a strong scattering link114 by means of adaptive optics and machine learning.
However, none of the aforementioned works achieved the expected multi-DoF multiplexing gain. Taking112 as an example, an aggregate rate of 2.56 Tbps was achieved by offline aggregation of 32 channels, comprising two polarizations, eight OAM modes, and two spatially concentric rings, with a single-channel rate of 80 Gbps. Yet, the reported optical signal-to-noise ratio (OSNR) penalty, i.e., the additional link budget required to compensate for performance degradation across different channels, indicates that the result still falls into the category of sublinear multiplexing gain. For the inner and outer rings, the OSNR penalty was generally between 2 dB and 4.5 dB. This result highlights that the crosstalk among spatial, polarization, and mode multiplexing is the primary cause of this sublinear gain. Disparate channel responses for sub-channels, non-ideal demultiplexing processes, or errors from optical components all contribute to observable crosstalk, which has become a long-standing challenge in the field. Consequently, reducing or eliminating crosstalk has been a primary goal of many studies, all aimed at resolving the “1 + 1 < 2” sublinear multiplexing gain problem.
The underlying reason is that in OWC dominated by polarization-intensity or OAM-intensity modulation, most studies rely on homogeneous polarization modulation115,116 or OAM mode shift-keying117,118, both of which rely on physical information carriers that are highly susceptible to channel disturbances, such as turbulence, scattering, and absorption. While augmenting these modulation schemes with other physical properties of the same DoF—such as time-varying control of the light field to evade periodic channel perturbations—is a viable approach for more robust OWC, these incremental schemes do not fully exploit the essential properties of the information carriers. At best, they can only approach the “1 + 1 = 2” linear multiplexing gain prediction. Therefore, to achieve a breakthrough beyond the crosstalk-induced “1 + 1 < 2” problem, it is necessary to return to the physical essences of the information carriers.
However, a vectorial light field itself is nothing more than just a direct superposition of polarization and mode DoFs. Even with inhomogeneous polarization or modes, it is not immune to the crosstalk common in conventional homogeneous polarization multiplexing. Another issue with vectorial light is the overlap between its spatial mode DoFs and spatial DoFs, and there has been a long-standing debate on the mode diversity and stability of vectorial light. Here, we do not intend to delve into this specialized topic but merely point out that the essence of vectorial light, from its most basic formulation, is a form of inhomogeneous spatial multiplexing that still suffers from crosstalk in disordered media, and thus cannot escape the “1 + 1 < 2” sublinear multiplexing gain.
Fortunately, a series of examples from the optical fiber community points the way forward, showing how physical concepts can lead to major performance improvements in communication practice. First, based on the idea of mode-division multiplexing, Bozinovic et al.119 used OAM modes to achieve a data rate of 1.6 Tbps over a 1.1 km fiber, but still fell short of the “1 + 1 = 2” linear multiplexing gain. Subsequently, Gregg et al.120 discovered the conservation of higher-order OAM modes in special hollow-core fibers, which reduces crosstalk and enables near-degenerate coupling for OAM mode transmission, paving the way for further increasing channel capacity. Building on this principle, Ma et al.121 designed a topologically confined fiber different from traditional fibers based on total internal reflection. By exploiting the topological centrifugal barrier that OAM creates itself, the natural immunity to mode mixing of this fiber was demonstrated via parallel transmission of 50 modes over 480 m with crosstalk as low as −45 dB per kilometer. It must be emphasized that these works still operate within the “1 + 1 = 2” DoF multiplexing framework, and their core contributions lie in using the OAM conservation law in novel fibers to eliminate mode crosstalk. In fact, another breakthrough, a “1 + 1 > 2” multiplexing gain, exists and is discussed in Section “The “1 + 1 > 2” super-diversity in entangled VOWC”.
The “1 + 1 > 2” super-diversity in entangled VOWC
Vectorial light, described in the simplest terms, is the superposition of a non-uniformly polarized spatial light field. Specifically, a vectorial field \(\left|\Psi \right\rangle\) is generated at the transmitter by coherently superimposing two orthogonal spatial modes, \(\left|{\psi }_{1}\right\rangle\) and \(\left|{\psi }_{2}\right\rangle\), onto orthogonal polarization states, \(\left|H\right\rangle\) and \(\left|V\right\rangle\):
where the real coefficient α ∈ [0, 1] is a weighting parameter that partitions the total power between the two orthogonal polarization components. The bra-ket notation is used for consistency with related literature in this field122,123. Although a spatially inhomogeneous pattern emerges compared to traditional IM and PM schemes, from a communication perspective, this does not break through the framework of space, polarization, and mode multiplexing. However, the spatially inhomogeneous distribution of the field acts as a silver lining, indicating deeper physical mechanisms and novel communication schemes.
To visualize the basis of this paradigm shift, the physical mechanisms of scalar, multiplexed, and vectorial OWC are depicted in Fig. 2. IM, PM, and VM are shown as representative examples of these three paradigms, respectively. As illustrated in Fig. 2a, scalar OWC employs only a single DoF, typically the intensity, for information encoding, and is susceptible to DoF fading. Multiplexed OWC is fundamentally limited by crosstalk among the multiple DoFs as seen in Fig. 2b. For modulation schemes such as polarization shift keying (PolSK), channel-induced crosstalk between the orthogonal polarization DoFs degrades signal fidelity. This effect results in a collapse of the symbol constellation, as shown for the Poincaré sphere representation in Fig. 3b. In contrast, VOWC encodes information onto an invariant property of a coupled DoF structure. A prominent example of such an invariant is the degree of non-separability between the spatial mode and polarization DoFs, a quantity often referred to as classical entanglement or, more specifically, concurrence C96,123. A significant body of research has been dedicated to the study and application of classical entanglement in optical fields. A key conclusion from these studies is that concurrence is conserved during propagation through any unitary channel, i.e., a channel that only imparts pure phase disturbances such as atmospheric turbulence. Under such conditions, the concurrence of the received field, \(\widehat{C}\), remains identical to the transmitted value C
which was demonstrated in ref. 111. This conservation law is the cornerstone of VOWC’s robustness, as the information carrier is inherently immune to the fading and crosstalk effects that degrade conventional systems, as conceptually illustrated in Fig. 2c. The generation and measurement of concurrence form the basis of the communication link. At the transmitter, a specific concurrence value is encoded by controlling the relative weight a of different polarizatins, of the two orthogonal components of the vectorial field as in Eq. (1), according to the relation
At the receiver, the concurrence of the propagated field is determined by measuring the global Stokes parameters (S0, S1, S2, S3). These are obtained by integrating the powers in four polarization projections: horizontal (PH), vertical (PV), diagonal (PD), and right-circular (PR). The concurrence is then calculated as:
This basis-independent measurement protocol ensures that the invariant can be robustly decoded. Several visual elements in Fig. 2 are intentionally designed to clarify these concepts. Specifically, in Fig. 2c, a topologically stable knot symbol is used to represent the invariant property of the vectorial light field. This stands in contrast to the intertangled dashed lines in Fig. 2b, which illustrate the crosstalk that limits multiplexed systems. Furthermore, the connection points between the DoFs, abstracted as lines, are highlighted with red circular markers to emphasize the concept of entanglement. Consequently, while the received coupled structure in Fig. 2c may experience global transformations such as rotation, its internal topological connectivity is preserved, visually demonstrating the robustness of the invariant.
a In scalar OWC, information encoded on a single DoF is susceptible to channel fading. b In multiplexed OWC, information on multiple DoFs is susceptible to crosstalk. c In vectorial OWC, information is encoded on a physical invariant (e.g., entanglement or topology) of coupled DoFs, which is robust against channel disturbances, thereby preserving information integrity.
a IM is susceptible to optical power fading and scintillation. b PM suffers from channel-induced depolarization. c VM leverages the robustness of concurrence as a physical invariant despite channel distortions, thereby achieving near-zero symbol errors.
Figure 3 provides a quantitative validation of this conceptual framework with the basic pulse amplitude modulation (PAM) schemes. It presents numerical results124 comparing the end-to-end performance of the three modulation schemes, including IM PAM, 4-ary PolSK, and VM PAM, under simulated turbulent and scattering conditions. The results show that while the symbol fidelity of IM and PM degrades severely due to power fading and depolarization, respectively, the performance of VM (specifically, concurrence modulation) remains highly robust, achieving near-zero symbol errors.
Guided by this physical intuition and empirical evidence, we now delve into the theoretical underpinnings of this robustness. In the research conducted under the general framework of singular optics over three decades, some works have shifted away from classic goals like seeking high numbers of available modes or customizing special optical paths, focusing instead on how to achieve classical entanglement using inhomogeneous spatial modes. The primary motivation for this research is to construct quantum entanglement states in classical light fields to address practical issues in quantum systems, such as decoherence and the difficulty of entanglement preparation, and to simulate and exploit quantum phenomena in a relatively more accessible optical regime. Due to the coupling effect between the mode and polarization DoFs of vectorial light, that is, these two dimensions are not mutually independent, as mesoscopic light modes and polarization correspond to microscopic OAM and SAM, respectively. In this case, these two intrinsic DoFs of vectorial light exhibit inseparability, which directly resembles and corresponds to the properties of quantum entangled states.
A series of works has established the theoretical basis and technical schemes for predicting, analyzing, and measuring this degree of angular momentum entanglement in vectorial light. An important conclusion is that this physical quantity, known as vectorness or concurrence, is conserved in unitary systems, meaning it remains constant in channels with pure phase perturbations. Inspired by this, Singh et al.111 used concurrence as an information carrier to achieve error-free OWC in turbulence, bringing new insights to the wireless community.
The trick here is that, in the original “1 + 1 = 2” polarization and mode multiplexing systems, the addition of concurrence acts as a game changer, giving rise to a new “1 + 1 > 2” super-diversity gain. We carefully explain here why this is super-diversity and not super-multiplexing. It must be emphasized that the primary property of this entangled DoF is its robustness against channel impairments as seen in Eq. (1), rather than serving as an independent information-carrying channel to provide additional diversity order. The theoretical basis for this reliability in unitary channels has been rigorously demonstrated in ref. 111. Although it depends on the multiplexing polarization and OAM DoFs, its ease of control and measurement, combined with its robustness in unitary systems, makes it a cornerstone for the evolution of scalar OWC to VOWC. Therefore, our focus shifts from the capacity gain brought by multiplexing to the reliability gain inspired by concurrence itself. This is not a super-linear increase in data rate but refers to an enhancement in the system robustness against channel impairments, based on a non-traditional physical quantity that surpasses the predictions of all conventional diversity models. As an analogy, we can envision twisting information-carrying channels into a tightly wound stranded rope, whose overall strength or reliability is greater than the sum of the strengths of the independent strands, as depicted Fig. 2.
This DoF entanglement brings a significant paradigm shift to information-carrying schemes in disordered media. However, when the channel experiences non-pure-phase energy perturbations, that is the disturbance is not unitary anymore, such as strong scattering and receiver noise, its robustness diminishes. This calls for further work to find classical light field entanglement in contexts broader than unitary systems and to develop novel field-level and signal-level specialized tools to bring the “1 + 1 > 2” super-diversity promise of VOWC to the real world. Concurrence represents the optical simulation of two-body classical entanglement, yet more research125,126,127 is focusing on using classical light to simulate multi-body entanglement, indicating a new physical mechanism in multi-DoF communication, namely the “1 + 1 + 1 > 3” vision.
While the term is not yet widely established, we find it necessary to introduce VM as a concept to unify a growing body of research that moves beyond traditional IM and PM. We define VM as any modulation scheme that encodes information onto the intrinsic properties of a vectorial light field, particularly its structural robustness, for transmission through disordered media. The work by Singh et al.111, which utilizes the invariant of concurrence as an information carrier, stands out as a preliminary but vital example. Other instances of VM would include shaping the vectorial wavefront128 or coherence structure129 for enhanced information acquisition. In essence, VM refers to a class of techniques that exploit the rich physical nature of VFSO to advance OWC, sensing, and imaging.
To systematically summarize the distinctions, Table 1 provides a comparative analysis of three OWC paradigms (scalar, multiplexed, and vectorial) across several key features. As highlighted therein, VOWC represents a fundamental paradigm shift from conventional, capacity-oriented multiplexing to a new, reliability-oriented approach based on communication with physical invariants. This conceptual difference underpins the challenges and opportunities discussed in the subsequent sections.
Case study: robust PAM-64 OWC in turbulent and scattering media via vectorial modulation
High-speed optical interconnections widely utilize PAM schemes to increase data rates130. However, scaling PAM to higher orders faces certain challenges due to the limitations of traditional intensity modulation and direct detection (IM/DD) systems and channel impairments131. Specifically, IM/DD receivers distinguish discrete intensity levels, hindering reliable differentiation of small intensity variations between closely spaced adjacent levels, particularly for high-order PAM (N ≫ 4). To address this limitation, VM systems, based on the properties of vectorial light, offer a compelling alternative111. VM leverages the concept of concurrence, which quantifies the non-separability between a light field’s polarization state and spatial mode96,123. While previous studies have primarily focused on demonstrating error-free links by exploiting the inherent robustness of concurrence to channel distortions132, the same robustness can be also utilized to increase the achievable order of PAM and other modulation formats.
Inspired by these prior works, this section explores the application of VM systems to increase the available modulation order of PAM, specifically PAM-64. We conduct simulations utilizing a wave optics toolbox to model turbulent and scattering FSO channels, incorporating a mixed Poisson and Gaussian noise model to represent realistic polarized receivers. The simulation includes applying field-level digital signal processing (DSP) techniques as post-detection processing to the received fields, aiming to mitigate channel distortions and noise and to minimize the deviation of the received concurrence from the transmitted values, thereby enhancing bit error rate (BER) performance. Our numerical results demonstrate near error-free PAM-64 performance for high signal-to-noise ratio (SNR).
Unlike conventional point-like intensity measurements in photon detectors, concurrence is a scalar and global quantity derived from the spatially resolved profiles of different polarized fields. This measurement approach inherently integrates information across the beam’s spatial distribution, offering enhanced resilience to localized distortions and fluctuations compared to direct intensity detection111. This provides a more robust means of distinguishing signal states, especially in distorted channels. These properties suggest that VM holds important potential to increase the achievable order of PAM schemes by enabling robust discrimination of symbols with reduced spacing, thereby paving the way for higher data rates using existing infrastructure.
Numerical methods
Figure 4 illustrates a potential implementation of a VOWC system, which serves as the framework for the numerical simulations presented in this work. The system architecture comprises three primary segments: a transmitter, a disordered optical channel, and a receiver. Distinct from conventional OWC, the transmitter incorporates a vectorial modulator. In our specific simulation, this modulator first converts input data (e.g., pixel values from an image) into a bit-stream. This stream is then mapped to PAM symbols, where each symbol level corresponds to a specific value of concurrence. Finally, the modulator generates a sequence of vectorial beams, each tailored to represent a PAM symbol, for transmission through the channel.
The vectorial modulator and detector are utilized to encode and decode information bits onto light field invariants, such as concurrence or topology, via Stokes field analysis. At the receiver, adaptive optics or field-level DSP are employed as field-domain optimizers to mitigate channel distortions.
The channel introduces various impairments that degrade the signal, including link attenuation from absorption and misalignment, as well as distortions from particle scattering and turbulent refraction. At the receiver, a polarized imaging sensor (e.g., complementary metal oxide semiconductor, CMOS or charge coupled device, CCD) captures four intensity images of the distorted beam, (IH, IV, IR, ID), corresponding to different polarization projections. The captured data is further corrupted by receiver-side effects such as inherent device noise. The received intensity images are then processed by a vectorial detector, which may include a field-level optimization stage to mitigate channel distortions and noise before calculating the concurrence value for symbol demodulation.
While a comprehensive analysis of all performance-degrading factors is beyond the scope of this Perspective, the impact of turbulent, scattering effects, and receiver noise is quantitatively investigated in Fig. 5. The results shown therein highlight the necessity of employing field-level optimization techniques, particularly in low SNR regimes.
a Visual evidence of optical field restoration from distorted and noisy measurements. b Corresponding BER performance, showing near error-free PAM-64 transmission by approaching the vacuum limit.
To mitigate channel distortions and noise, post-detection processing steps are applied to the captured intensity images. These processing steps simulate field-level DSP functionality and denoising. We investigate three specific processing techniques applied to the noisy intensities: conventional iterative phase retrieval (PR, specifically the Fienup algorithm), total variation-based PR (TV-PR)133 for its robustness to Poisson noise, and the fractional moment toolbox in the Radon domain (FMR)134 for its noise resistance. The iterative PR is a method analogous to a wavefront sensor-based field-level DSP correction calculation operating on intensity data, while TV-PR and FMR function primarily as sensorless field-level DSP or advanced denoising modules. From the processed intensity images obtained after applying PR, TV-PR, or FMR, the concurrence value for each transmitted symbol is calculated according to the method described in ref. 111. Finally, PAM symbol demapping is performed based on the calculated concurrence values to recover the transmitted bit-stream and determine the BER.
Demonstration of PAM-64
Parameters utilized for numerical evaluation are set as follows. The transmitted beam utilized \({a}_{1}\left|{\,{\rm{LG}}}_{p=0}^{l=1}\right\rangle \left|\,{\rm{H}}\right\rangle +{a}_{2}\left|{\,{\rm{LG}}}_{p=0}^{l=-1}\right\rangle \left|\,{\rm{V}}\right\rangle\) mode at a wavelength λ = 5.32 × 10−7m with an initial beam waist w0 = 3 × 10−4m, where a1 and a2 are defined with specific values of concurrence C111. Concurrence was quantized with a step ΔC = 1/N, enabling PAM-N formats where N = 64. Simulations were performed over 50m FSO channels by phase screens generated based on established power spectral densities135,136, characterizing by moderate turbulence (Rytov number \({\sigma }_{\,{\rm{R}}}^{2}=1.8546\times 1{0}^{-1}\)) and specific scattering parameters (particle size 500λ, refractive indices of background medium and particles are 1.33 and 1.59), respectively.
The empirical BER performance is compared across different channel scenarios in Fig. 5. The figure plots BER versus SNR for ideal (vacuum) links, links impaired by turbulence and scattering, and links that additionally include receiver noise effects. The impact of receiver noise and denoising is illustrated by comparing solid (noisy) and dash-dotted (noise-free ideal detection) curves. These results highlight the significant BER performance boost provided by field-level DSP in mitigating channel impairments. Notably, for PAM-64 transmission over 50m links c.f. Fig. 5b, field-level DSP compensation facilitated near error-free performance when SNR≥32.5dB. This was achieved despite channel distortion and receiver noise, representing a key finding of this section.
We proposed an field-level DSP-assisted VM systems, enabling robust PAM-64 transmission in challenging FSO channels with turbulence and scattering. We emphasize the importance of concurrence as a vital property to unlock the vast potential of vectorial light, going beyond treating these beams merely as simple extensions of scalar beams with spatial modes. Our findings aim to inspire further research in these areas towards harnessing the full potential of vectorial light for future optical communication systems.
From scalar to vectorial OWC: challenges, opportunities, and visions
This section focuses on the extensive research challenges and certain opportunities in the evolution of OWC towards the era of vectorial light. We discuss how this paradigm shift introduces new toolkits and application prospects to the wireless communication community, ensuring a great expansion of its theoretical and technical scope. First, we re-examine light transport and channel modeling from a physics perspective, exploring how to precisely describe the propagation of vectorial light fields in disordered media. This requires moving beyond traditional scalar models to establish new theoretical and simulation frameworks capable of capturing the true evolution of each DoF of the light fields. Second, we emphasize that VOWC necessitates a system characterization upgrade from the channel matrix to the channel tensor, a concept closely related to the channel operator and transmission matrices in optical physics. Subsequently, based on the channel tensor model, we argue that performance optimization in VOWC must shift from the traditional electrical domain to the physical domain. This new paradigm promotes the integration of communication and imaging optimization. Furthermore, precise physical modeling naturally enables environmental optical sensing, laying the foundation for the multi-functional paradigm of ISAC. Finally, we envision how cutting-edge advances in VFSO can integrate tools such as cohomology and topological physics into the potential toolbox of wireless communication, thereby expanding the theoretical boundaries of wireless community.
Challenges of physical light transport modeling
How to accurately and rapidly solve for the propagation of each physical quantity and DoF of vectorial light fields in a practical optical wireless channel, both theoretically and numerically, and ensure consistency with real-world light transport behavior? This is a core challenge for statistical, wave, and ray optics, and a common problem in engineering fields such as OWC, computational imaging, and computer graphics. Currently, this challenge manifests in three main aspects: (1) the characterization of random media in theoretical solutions, (2) the trade-off between complexity and accuracy in simulating the light fields propagation in random media, and (3) the accurate solving of the physical quantities carried by the light fields.
Taking the most common turbulent and scattering media in optical wireless channels as an example, existing modeling methods fall into two main mechanisms. Ray tracing, originating from the radiative transfer equation, is mostly used for simulating scattering and absorption channels. Split-step beam propagation, originating from wave optics, is mostly used for simulating turbulent channels. In recent years, the applications of ray tracing has been extended from line-of-sight paths to non-line-of-sight ultraviolet channels137, indoor RIS-assisted wide-beam illumination138,139, and cross-media interfaces140. In addition to scene expansion, related modeling work continues, including vector versions of the radiative transfer equation141, hardware acceleration142, and multi-domain channel modeling for MIMO systems143,144,145,146,147. However, when factors like turbulence are involved, these works often simplify them into a channel fading coefficient148,149,150, lacking detailed consideration of intensity fluctuations or dynamic transition.
In contrast, for modeling the effects of turbulence, researchers starting from the spatial power spectrum model of optical turbulence135,151,152,153,154,155 can now conduct more detailed analyzes from a statistical optics perspective, and have gradually established unified channel models for Gaussian and OAM beams in turbulence156,157,158,159. However, most of the aforementioned works have been carried out by choosing either ray tracing or wave optics modeling, resulting in an incomplete integration of turbulence and scattering effects. Although some research has attempted to combine both frameworks160 or propose a unified wave optics method136, existing modeling techniques still have plenty of room for improvement in terms of theoretical accuracy, precision, and applicability.
Specifically, existing frameworks share common limitations: the commonly used ray optics framework lacks the characterization of the partial coherence of the light field, meanwhile, the wave optics framework is limited by simplified angular spectrum propagation settings and idealized phase screen models. More crucially, both frameworks mostly operate in the two-dimensional field domain for paraxial light, lacking a complete characterization of non-paraxial light fields. These constraints make it difficult for current simulation methods to be cross-verified with measured channel results, a challenge that is widespread across various complex scenarios, from narrow laser cases to wide illumination cases.
The above analysis points to a major challenge in the basic level research of VOWC, that is, how to solve, simulate, and verify the propagation of vectorial light field characteristics and physical quantities in complex media at the theoretical, numerical, and experimental levels? We believe the solution path should be based on the integration and improvement of physical models. On one hand, achieving an integrated characterization of multiple optical effects in complex natural environments within the wave optics framework, on the other hand, performing a coherent modification of the ray tracing framework. By cross-verifying these two models with statistical optics theory, the correlation between the fading characteristics of light and the fading of information-carrying physical quantities can be established, thereby reconstructing the commonly used fading channel coefficients in wireless communication with rich physical connotations.
Challenges in channel characterization and optimization
The evolution from scalar to vectorial paradigms poses major challenges to system modeling, channel characterization, and performance optimization. The root of these challenges lies in the dimensional shift of the information carrier: from a one-dimensional signal to a two-dimensional optical field. Figure 6 provides a conceptual framework for this paradigm shift and outlines the corresponding engineering solutions. As illustrated in Fig. 6a, b, the transition to VOWC necessitates an upgrade of the system model from an abstract, signal-level description (e.g., CSI) to a physical, field-level propagation model (e.g., MSI). Consequently, the conventional channel matrix, H, evolves into a propagation operator, \({\mathcal{P}}[\cdot ]\), whose discrete representation is a channel tensor. This shift in modeling further requires that the receiver architecture evolves from signal-level processing (e.g., DSP) to field-level optimization (e.g., wavefront processing). Figure 6c demonstrates the practical feasibility of this MSI-based approach. It shows a closed-loop validation where the physical structure of the channel operator \({\mathcal{P}}[\cdot ]\) is first acquired via optical tomography and then utilized in a forward propagation simulation. The high fidelity between the true input field E(x) and the retrieved field \(E(\widehat{x})\) (with structure similarity index measure, SSIM above 0.99) confirms the validity and self-consistency of the physical model. This framework, grounded in a field-level physical description, forms the basis for the subsequent discussion on VOWC’s specific challenges and opportunities.
a Evolution of system modeling from CSI-based abstract signal-level description to MSI-based physical light field transport. b Transition from the conventional channel matrix to a channel tensor, which serves as the discrete representation of the propagation operator. c Preliminary validation of the channel tensor through high-fidelity wavefront reconstruction (including intensity and phase) based on the retrieved MSI operator.
In the context of VOWC, the collaborative mechanism of multiple DoFs and physical quantities no longer aligns with traditional communication system modeling and optimization methods, creating an urgent need for new technical constructs. The root lies in the fundamental shift in how information is carried: in VOWC, the non-uniformly distributed intensity and polarization information across the entire two-dimensional light field jointly constitute the global information carrier. This paradigm shift necessitates a reconsideration of the signal, SNR, and system model in VOWC, triggering entirely new field-level optimization problems.
Existing research provides important references for this direction. In terms of system performance, numerous works have evaluated the performance of Gaussian or OAM beams under various channel impairments156,158,161,162,163,164,165,166. Concurrently, a series of works aimed at improving system performance through light field optimization167,168,169,170 have completed field-level optimization for systems like OAM communication using methods from optical imaging such as phase retrieval and machine learning, offering new perspectives on field-level optimization beyond DSP.
Although these explorations exist, most have not explicitly proposed the channel tensorization problem in the cases of 2D light field communication. Klug et al.106 replaced the traditional channel matrix with a channel operator. In such a scenario, as demonstrated by Miller99, the channel is effectively promoted to a four-dimensional tensor between two 2D planes. This insight suggests that future VOWC system design should begin with a high-dimensional channel representation to reshape the signal and system models. However, Klug et al.106 treated light field propagation as a 2D diffusion process, while the resulting channel eigenmodes are robust, this view, which simplified the nonparaxial physical reality, limits the model’s applicability. Starting from this point, for the three dimensional (3D) propagation of various non-paraxial light fields, a universal, accurate, and physically faithful reconstruction of the high-dimensional light field channel, signal, and system model can be developed, beginning with the discretization of the extended Huygens–Fresnel principle.
This systematic reconstruction includes the fading of information-carrying physical quantities, the physical process from light field to abstract signal, and the cascaded characteristics of point/field receivers. Specifically, the signal reconstruction begins by recognizing the change in communication symbol dimensionality: under traditional time-domain modulation, a single timeslot symbol evolves from a 1D signal to a 2D field signal, thus the channel evolves from a matrix to a tensor. After signal reconstruction, the SNR evaluation must also be re-evaluated. Given the lack of a clear SNR definition in camera-based OWC, a globally defined SNR model should be proposed: the undisturbed and propagated light fields at the receiver serve as the standard signal, and the total power of the amplitude difference between the actual received field and the standard signal at each pixel is considered as the noise power. Furthermore, a vectorial light field receiver, e.g., a polarized CMOS, can be modeled as a cascaded channel with Gaussian and Poisson noises. Based on this reconstruction of the signal and SNR, a novel VOWC system model is established, which replaces traditional communication modules with a series of vectorial light field-related modules, including symbol mapping, spatial multiplexing, tensor channel, and light field detection.
Finally, under the VOWC architecture, performance optimization must shift from the traditional electrical-domain signal-level paradigm to a 2D optical-domain field-level optimization paradigm, which is strongly related to wavefront engineering in optical imaging and sensing works. Logically, optimization can be made in three phases: (1) before light field reception, (2) after reception but before signal abstraction, and (3) after signal abstraction (traditional DSP optimization). However, existing research paths have clear limitations. In the optical imaging community, field-level adaptive optics (AO) is a well-established method for information interpretation from passively acquired images. These AO techniques, which can be categorized as both sensor-based and sensorless approaches, serve as a foundational example of field-level DSP. However, in the context of OWC, where the goal is to recover information from actively modulated optical fields, tailored field-level DSP techniques are still under development. On the other hand, traditional DSP algorithms that rely on point receivers are largely ineffective in inhomogeneous VM case and 2D field-level reception scheme.
To this end, we advocate for an upgrade of the optimization paradigm on two levels. First, by elevating the traditional point-based DSP algorithms to the spatial dimension to create a field-level DSP. Second, to undertake a communication-oriented transformation of existing imaging AO technology. This paradigm shifts include three challenges: (1) objective transformation, i.e., using communication performance like BER as the optimization target; (2) constraint transformation that uses the VOWC channel and receiver limitations as constraints; and (3) algorithm reconstruction, i.e., rebuilding AO methods to handle new information carriers like singular and topological light fields. Ultimately, the ideal optimization paradigm for VOWC should be a cross-domain joint optimization aimed at optimal reception and maximum information extraction, which requires the hybrid use of the developed communication-transformed AO in optical-domain and electrical-domain DSP at the receiver.
Toolkits and vision updates
The study of vectorial light fields has introduced many new theories and tools to FSO, which directly form a potential toolbox for VOWC and are expected to bring brand-new insights into its applications. Utilizing the intrinsic multi-DoFs of vectorial light to sense the propagation channel and medium171,172,173,174,175 will rapidly advance the development of ISAC in VOWC. This functional extension of vectorial light broadens VOWC from communications-only to multiple other focused tasks, such as wireless sensing and imaging. The core idea is that, on one hand, information is transmitted under known channel conditions via a quasi-static channel assumption, on the other hand, MSI is acquired by transmitting known pilot signals based on vectorial light, achieving environmental sensing compared to conventional CSI-based channel estimation. This is where vectorial light brings a paradigm shift to ISAC. For instance, as reviewed in ref. 173, the spatial structure of the vectorial light is highly sensitive to an object’s geometric profile and motion, providing a direct means for depth and shape estimation. Concurrently, the polarization state of the returned light is directly modulated by the target’s surface characteristics. As demonstrated in the context of polarimetric imaging176, a detailed, spatially-resolved analysis of the full Stokes parameters allows for the precise characterization of material properties, such as birefringence, which are related to an object’s reflectivity and surface texture. Crucially, ref. 176 also provides an engineering manual for how these distinct DoFs, both spatial mode (for depth) and polarization (for texture), can be captured simultaneously in a single snapshot. A complementary approach exists that forgoes spatial resolution in favor of temporal resolution, it leverages the concurrence of vectorial light to perform high-speed kinematic sensing177.
In the wireless community, sensing typically refers to target-oriented tasks like distance ranging178,179,180, while in the optical community, environmental sensing is more prevalent. Vectorial light is expected to enable a functional upgrade for wireless ISAC: achieving environmental sensing on top of target sensing, realizing channel transparency on the basis of channel sounding. We emphasize that vectorial environmental sensing not only brings a major upgrade to ISAC, a core function of 6G, but also promotes the fusion of multiple tasks in optical engineering, including communication, sensing, and imaging, bringing a fresh interdisciplinary perspective to 6G and beyond.
However, more importantly, theoretical advances in VFSO can bring a richer physical landscape to VOWC, along with a broader theoretical and application scope. Cohomology theory has been used for the arbitrary boundary condition extension of FSO skyrmions fields90 to ensure the conservation of the topological number in real physical systems. Here, cohomology theory is applied to generalize the boundary conditions of the light field, allowing for the observation of topological quantities by analyzing the spatial topology of different regions, thereby extending classical skyrmions to a richer and more robust topological description. This provides an important perspective for the practical application of skyrmionic light fields. When the beam’s boundary conditions are disrupted by turbulence and scattering, this cohomology-based optical quasi-particle still has the potential for topological conservation. In free-space channels, Wu et al.181 pioneered the construction of a composite topology with both quasi-particle texture and point defects, achieving controllable conversion between different topological states and introducing a groundbreaking 3D composite topology to FSO. The greater significance of this work lies in bringing topological optics from a field requiring special engineering means (like nano-optical devices) into the classical domain of FSO, placing topological physics directly before FSO engineering. This brings rich physical structures and universal physical connotations to the future of the wireless community, including VOWC. As an example, Zhang et al.182 has implemented VOWC using defect states, a practice underwritten by rich physical insights.
Conclusions
In OWC, traditional methods based on IM or homogeneous PM face limitations in fully exploiting the rich characteristics of light. VOWC, with its intrinsic multi-DoF characteristics, is expected to break through traditional limitations and bring about major performance improvements. Based on the core idea of seeking invariants in disordered media, the multi-DoF coupling phenomenon in vectorial light fields introduces super-diversity gain into the existing OWC regime, directly enabling stable information transmission in disordered media. During the evolution from scalar OWC to VOWC, although certain challenges have emerged in aspects such as light field transmission modeling, channel characterization, and system optimization, it has also brought novel theoretical tools, physical connotations, and engineering perspectives to OWC. While providing a potentially upgrade to core 6G visions like ISAC by inherently fusing tasks such as communication, sensing, and imaging, VOWC greatly expands the theoretical and application frontiers of the wireless communications field. It leverages optical physics to drive physical-layer advancement in OWC during the shift from the current digital era to a future of intelligence.
Data availability
The data supporting the findings of this article are available from the corresponding author upon reasonable request.
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Acknowledgements
The authors would like to thank Prof. Ran Liao for useful discussions, particularly regarding inhomogeneous polarization, optical turbulence and scattering phenomena, and the multi-scale description of light-matter interactions. The authors acknowledge Dr. David Marco Castillo for the open-source VectorBeamsMATLAB toolbox, available on GitHub124 under the GNU General Public License, which was utilized for the generation of vectorial light fields in our simulations. The authors also acknowledge the open-source Seawater Thermophysical Properties Library (https://www.web.mit.edu/seawater)183, the Thermodynamic Equation of Seawater 2010 (TEOS-10) toolbox (https://www.teos-10.org)184, and the Wave Analysis for Fatigue and Oceanography (WAFO) toolbox (https://www.maths.lth.se/matstat/wafo)185,186, which were instrumental in the modeling of underwater turbulence. This work was supported by the National Key Research and Development Program of China under Grant 2024YFB4303402.
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W.D., Y.D., and J.S. conceived the work and suggested the outline of the paper. W.D. and Y. D. wrote the main manuscript text. W.D. and T.W. prepared all figures. X.G., Z.L., and J.S. revised the manuscript.
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Dai, W., Dong, Y., Wei, T. et al. Vectorial optical wireless communications: bridging optical physics and engineering for 6G and beyond. npj Wirel. Technol. 2, 11 (2026). https://doi.org/10.1038/s44459-025-00018-7
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DOI: https://doi.org/10.1038/s44459-025-00018-7
