In free-space or in optical fibers, orbital angular momentum (OAM) multiplexing for information transmission has been greatly developed. The light sources used were well coherent communication bands, and the fibers used were customized. Here, we use an 810 nm femtosecond laser to generate optical vortices carrying OAM and then feed them into two kinds of commercial step-index few-mode fibers to explore the transmission characteristics of OAM modes. We also propose a method without multiple-input multiple-output digital signal processing to identify the input OAMs. It is of great guiding significance for high-dimensional quantum information experiments via the OAMs as a degree of freedom, using the light generated by the spontaneous parametric down-conversion as the source and the commercial fibers for information transmission.
In free-space or in optical fibers, orbital angular momentum (OAM) multiplexing for information transmission has been greatly developed. The light sources used were well coherent communication bands, and the fibers used were customized. Here, we use an 810 nm femtosecond laser to generate optical vortices carrying OAM and then feed them into two kinds of commercial step-index few-mode fibers to explore the transmission characteristics of OAM modes. We also propose a method without multiple-input multiple-output digital signal processing to identify the input OAMs. It is of great guiding significance for high-dimensional quantum information experiments via the OAMs as a degree of freedom, using the light generated by the spontaneous parametric down-conversion as the source and the commercial fibers for information transmission.
Orbital angular momentum (OAM) of photons provides a promising approach to enhance the capacity, robustness, and functionality of quantum communication systems in optical fibers. With many twist states available, OAM enables high-dimensional encoding, significantly increasing data rates and noise tolerance. This review explores sources, channels, and system architectures for OAM-based quantum communication in fibers. It compares free-space and integrated emitters, discussing in-fiber pair generation and mode conversion pathways that produce fiber-ready single photons and entangled states. For the channels, it details design principles and trade-offs for step-index and ring-core fibers that minimize intermodal coupling and reviews milestones in kilometer-scale single-photon transmission and high-dimensional entanglement transport. On the system side, the review examines coupling, multiplexing, and detection techniques—including mode (de)multiplexers, lanterns, and programmable sorters—and discusses transmission-matrix-based control methods to mitigate dispersion and bending effects. The review concludes with practical guidance and open challenges, such as improving mode selectivity and stability under real-world conditions; developing compact, efficient detectors for many modes; and integrating co-designed error correction schemes. These directions aim to bridge laboratory demonstrations with the deployment of scalable, high-dimensional fiber networks that harness OAM to significantly boost capacity, resilience, and functionality.
Light carrying orbital angular momentum (OAM) has exciting applications, including the studies of fundamental quantum physics, optical manipulation and trapping of particles, astrophysics, high-precision optical measurements and optical communication, etc. In quantum information field, a photon encoded with information in its OAM degrees of freedom enables networks to carry significantly more information and increase their capacity greatly due to the inherent infinite degrees of freedom for OAM. Therefore it is no surprise that many groups and researchers are active in building up a high-dimensional quantum network and many important progresses have been achieved during the past years. To realize a long-distance quantum communication, a quantum repeater has to be used to overcome the problem of communication fidelity decreasing exponentially with the channel length, where, quantum memories for photons, used for storing quantum information, which have been realized successfully during the past decade in many systems such as a cold/hot atomic system, a solid matter, a diamond, and others, are key components consisting of a quantum repeater. Photons acted as information candidates can connect different quantum repeaters. Long distance quantum communication requires the wavelengths of photons are situated in the low-loss communication windows, but most quantum memories currently being developed for use in a quantum repeater work at different wavelengths, only few memories can work in low-loss communication windows. Furthermore, the signal stored is an attenuated coherent light and has the Gaussian mode. Though the storage of photonic entanglement at telecom wavelength is realized in an erbium-doped optical fibre recently, the spatial mode used is Gaussian mode. Quantum memories for photons with OAM have recently been realized, but all work at different wavelengths. So a quantum interface to bridge the wavelength gap is necessary.
In the realm of quantum information processing, harnessing high-dimensional photonic systems provides a pathway to overcome limitations of traditional two-level systems. Orbital angular momentum (OAM) of light has emerged as a powerful tool for creating and manipulating high-dimensional entanglement, promising increased information capacity and enhanced security in quantum communication protocols. However, conventional methods like spontaneous parametric downconversion encounter challenges due to non-uniform production rates of Laguerre–Gaussian modes. This study explores the potential of spontaneous four-wave mixing in ring-core fibers (RCFs) as a viable platform for generating OAM photon pairs with tailored spectral and spatial properties. We show that by controlling the topological charge of pump photons, correlated, uncorrelated, and anti-correlated photon pairs can be engineered across arbitrary spectral ranges, essential for diverse quantum applications. Experimental noise characterization of the RCF-based source demonstrates a high coincidence-to-accidental ratio exceeding 4000, and a low heralded second-order correlation function ( g H (2) <0.005), which confirms its operation well into the single-photon regime. This work demonstrates the potential of RCFs as a versatile platform for generating structured photon pairs, paving the way for future high-dimensional quantum communication and information processing applications.
The beam with orbital angular momentum is a present domestic and foreign research key direction. Its application and development will bring the profound influence in the optical communications field. At the same time, light's orbital angular momentum promises potential applications in both classical and quantum optical communication. The research progress of the beam with orbital angular momentum and encoding information as light's OAM for free-space optical communication were reviewed in this article, the existing design method, mechanism and description methods of encoding information as light's OAM were discussed. In quantum communication, qudits can be encoded in photons using their OAM for creating high-dimensional entanglement based on entangled photon pairs from SPDC. In this paper, light's OAM is used as information carrier for classical and quantum communication, which is promising to ensures the security of atmospheric laser communication, improves the density and precision of information transmission. It is apparent that an efficient way to measure the orbital angular momentum of individual photons and light beams with good efficiency would be of potentially great importance for optical communications and quantum information. In view of the above, the measurements of orbital angular momentum of individual photons and light beams are analyzed and discussed in detail.
Light carrying orbital angular momentum constitutes an important resource for both classical and quantum information technologies. Its inherently unbounded nature can be exploited to generate high-dimensional quantum states or for channel multiplexing in classical and quantum communication in order to significantly boost the data capacity and the secret key rate, respectively. While the big potentials of light owning orbital angular momentum have been widely ascertained, its technological deployment is still limited by the difficulties deriving from the fabrication of integrated and scalable photonic devices able to generate and manipulate it. Here, we present a photonic integrated chip able to excite orbital angular momentum modes in an 800 m long ring-core fiber, allowing us to perform parallel quantum key distribution using two and three different modes simultaneously. The experiment sets the first steps towards quantum orbital angular momentum division multiplexing enabled by a compact and light-weight silicon chip, and further pushes the development of integrated scalable devices supporting orbital angular momentum modes.
The capacity of optical communication channels can be increased by space division multiplexing in structured optical fibers. Radial core optical fibers allows for the propagation of twisted light–eigenmodes of orbital angular momentum, which have attracted considerable attention for high-dimensional quantum information. Here we study the generation of entangled photons that are tailor-made for coupling into ring core optical fibers. We show that the coupling of photon pairs produced by parametric down-conversion can be increased by close to a factor of three by pumping the non-linear crystal with a perfect vortex mode with orbital angular momentum ℓ, rather than a gaussian mode. Moreover, the two-photon orbital angular momentum spectrum has a nearly constant shape. This provides an interesting scenario for quantum state engineering, as pumping the crystal with a superposition of perfect vortex modes can be used in conjunction with the mode filtering properties of the ring core fiber to produce simple and interesting quantum states.