Optical fibers are being widely utilized as radiation sensors and dosimeters. Benefiting from the rapidly growing optical fiber manufacturing and material engineering, advanced optical fibers have evolved significantly by using functional structures and materials, promoting their detection accuracy and usage scenarios as radiation sensors. This paper summarizes the current development of optical fiber-based radiation sensors. The sensing principles of both extrinsic and intrinsic optical fiber radiation sensors, including radiation-induced attenuation (RIA), radiation-induced luminescence (RIL), and fiber grating wavelength shifting (RI-GWS), were analyzed. The relevant advanced fiber materials and structures, including silica glass, doped silica glasses, polymers, fluorescent and scintillator materials, were also categorized and summarized based on their characteristics. The fabrication methods of intrinsic all-fiber radiation sensors were introduced, as well. Moreover, the applicable scenarios from medical dosimetry to industrial environmental monitoring were discussed. In the end, both challenges and perspectives of fiber-based radiation sensors and fiber-shaped radiation dosimeters were presented.

Magnetic field sensing plays an important role in many fields of scientific research and engineering applications. Benefiting from the advantages of optical fibers, the optical fiber-based magnetic field sensors demonstrate characteristics of light weight, small size, remote controllability, reliable security, and wide dynamic ranges. This paper provides an overview of the basic principles, development, and applications of optical fiber magnetic field sensors. The sensing mechanisms of fiber grating, interferometric and evanescent field fiber are discussed in detail. Magnetic fluid materials, magneto-strictive materials, and magneto-optical materials used in optical fiber sensing systems are also introduced. The applications of optical fiber magnetic field sensors as current sensors, geomagnetic monitoring, and quasi-distributed magnetic sensors are presented. In addition, challenges and future development directions are analyzed. Graphical Abstract

Thermally drawn multimaterial fibers have experienced rapid development in the past two decades owing to the high scalability, uniformity, and material and structure compatibility of the thermal drawing technique. This article reviews various multimaterial fibers based on different functional structures and their applications in disparate fields. We start from the functional structures achieved in optical fibers developed in the early stage of thermally drawn fibers. Subsequently, we introduce both typical functional structures and unique structures created in multimaterial fibers for varying applications. Next, we present the early attempts in breaking the axial symmetric structures of thermally drawn fibers for extended functionalities. Additionally, we summarize the current progress on creating surface structures on thermally drawn fibers. Finally, we provide an outlook for this trending topic towards wearable devices and smart textiles.

The multimode waveguide is essential for future mode-division-multiplexing optical interconnection systems to further improve data capacity. However, the complex waveguide design process based on numerical methods is time consuming and requires a lot of computational effort. By using machine learning trained models, one can find the rules from the observed data (sample) and use the learned rules (model) to predict the unknown or unobservable data quickly. In this paper, to accelerate the multimode waveguide design, several regression models consisting of fully connected and long short-term memory layers are employed to predict the effective refractive indices from the fundamental mode to fourth-order TE mode with various waveguide geometries. For air cladding waveguides, the percentages of eligible data whose prediction errors are less than 10 − 3 of different modes are 89.95%, 88.10%, 82.29%, 75.83%, and 71.19%. For S i O 2 cladding ones, they are 95.40%, 92.81%, 90.90%, 81.99%, and 86.39%. Based on these models, two kinds of mode multiplexers are designed, and coupling efficiency of higher than 85% is achieved.

The Kerr microresonators have aroused widespread interests for their ultrahigh integration, compatible fabrication and ultralow energy consumption. Similar to the traditional mode-locked fiber lasers, the microresontors can sustain the generation of dissipative solitons called cavity solitons relying on the double balance of gain and loss as well as nonlinearity and dispersion. The state of multiple solitons is common in the microresonator with anomalous dispersion. In particular, an ideal state named as soliton crystals is obtained when the multiple solitons have a equidistant arrangement. And recent experiments have successfullly observed soliton crystals in the Kerr microresonators. To intuitively reveal the formation and evolution dynamics of the multiple solitons and get insight into the underlying physical mechanisms of soliton crystals, we applied the nonlinear Fourier transform to project these states into nonlinear discrete spectrum. The discrete spectra of single soliton with different modulated background waves have been displayed, which can help distinguish different optical components. Then, the nonlinear spectrum evolution of normal multiple solitons state shows the typical nonlinear states of the intracavity field. And the equidistant solitons have the effects of power enhancement, whose spectral intensity is several times that of a single soliton state. Comparing with the discrete spectrum of the equidistant solitons, the solitons inside the soliton crystals interact with each other by the modulated background. Our results suggest that the nonlinear Fourier transform is a powerful technique to characterize soliton dynamics in the Kerr microresonator, which provides a new perspective to understand the interactions of cavity solitons.

The efficient and independent operation of power-over-fiber (PoF) and distributed acoustic sensing (DAS) has been demonstrated using standard single-mode fiber (SSMF). An optical power transmission efficiency (OPTE) of 6.67% and a transmission loss of ~1 dB/km were achieved over an 11.8 km fiber link, supporting both power delivery and distributed optical fiber sensing (DOFS). To minimize cross-talk, the system separates the power and sensing channels by an 88 THz bandwidth. In the experiment, the power and sensing light wavelengths are 1064 nm (continuous) and 1550 nm (pulsed), respectively. As the transmitted optical power increased from 0 W to 2.13 W, the DAS system successfully localized vibration sources with a resolution of 6.29 m and reconstructed phase information, confirming its ability to operate under high optical power. The reported scheme verifies the possibility of constructing the sensing-energy hybrid network based on a conventional optical fiber with the advantages of flexible layout and compatibility.