In this paper, a novel hollow-core ring photonic crystal fiber (HR-PCF) is proposed based on As ₂ S ₃ . It supports the transmission of up to 38 orbital angular momentum (OAM) modes. It is composed of a concentric ring cladding of air holes gradually increasing in diameter. In addition, the center also has a large circular air hole. A numerical simulation is accomplished using the finite-element method. Different geometrical parameters of the proposed HR-PCF include the number of air hole rings in the cladding and the background material. These parameters are varied to determine the optimal structure. The properties of the synthesized OAM vector modes are simulated and analyzed systematically and theoretically. Through the simulation of different parameters, we show that the optical fiber structure based on a three-ring cladding and As ₂ S ₃ material can support 38 OAM modes. This configuration also has better eigenmode characteristics, such as the effective refractive index difference between vector modes with the same topological charge number. This difference can exceed 10-4, preventing these modes from coupling to linear polarization modes. In addition, the vector mode dispersion curve becomes smoother with increasing wavelength, and the confinement loss remains low, ranging from 10 ^-10 -10 ^-9 dB/m. Moreover, we also discuss effective mode area and nonlinear coefficients and their applications. We also investigated that various effects on the dispersions by details of the proposed HR-PCF, such as air hole spacing between adjacent rings and the diameter of the center circular air hole. This system offers some promising applications for short-distance, high-volume communications due to the increased number of OAM transfer modes.

This article proposes an efficient thermoelectric temperature control system based on an improved proportional integral differential (PID) algorithm in which energy feedback technology is used to enhance thermoelectric cooling. In the proposed power management system, two groups of batteries are efficiently and alternatingly charged and discharged such that the information of the circuit can be monitored in real time. The PID algorithm is improved by using the idea of a state machine to control the thermoelectric coolers (TEC) through an H-bridge circuit with pulsewidth modulation. Finally, the energy feedback circuit combined with improved synchronous switching technology is designed to recycle the energy to drive the sensor. By inputting current of 3.1 A, a wide range of temperature control from 1.437 to 60.187 °C was implemented. While targeting a temperature of 10 °C at an ambient temperature of 22 °C, the proposed temperature control system had a control time of 30.5 s, compared with 287 s when using the conventional method, with an accuracy of 0.1 °C, and an error of only ±0.35 °C. The results confirm that electric energy at a peak voltage of 1.2 V and current of 24 μA can be recovered. The proposed energy feedback system can thus improve the efficiency of energy utilization of TEC from a peripheral circuit.

We firstly propose a PCF structure with semicircular air holes. We focus on investigating the properties of the PCF based on silica. It can support 66 OAM modes from the wavelength of 1.1 μ m to 1.7 μ m with most modes’ confinement losses keeping as low as 10 ⁻⁹ dB/m. The eigenmodes effective refractive index separation (Δn _eff ) between the HE _m+1,1 mode and EH _m−1,1 mode are above 10 ⁻³ . All the nonlinear coefficients are less than 4 w ⁻¹ /km and the minimum value is as low as 1.4 w ⁻¹ /km. The minimum value of chromatic dispersion is as low as 31.8 ps/(nm·km) at 1.55 μ m. Meanwhile, we also investigate the proposed configuration with multiple background materials. Among all of the selected background materials, the numbers of supporting OAM modes range from 64 to 76. Most values of Δn _eff between HE _m+1,1 and EH _m−1,1 (m = 2–17) modes can be kept above 10 ⁻³ . The results indicate that the designed configuration possesses great communication performance and material availability.

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Thermoelectric coolers (TECs) are widely used in state-of-the-art thermal management systems. Recently, there is a big trend to power TECs using thermoelectric generators (TEGs). Mainstream research efforts focus on attaining a higher figure of merit (ZT) of thermoelectric material, which now faces a great challenge. Alternatively, this article proposes a different approach to improve the performance of TEC, that is, integration of a TEG with a TEC. The TEG converts the collected heat energy into electric current, which reduces the power consumption and enhances the cooling capacity of the TEC. Using different methods of connecting the TEC and TEG, two thermoelectric collaborative cooling systems are proposed. Accurate SPICE models of the two cooling systems are established. The experimental results demonstrate that the discrepancy between the currents flowing through the TEC in the experiments and in the SPICE models is less than 4.8% on average. Based on the verified SPICE models, the proposed TEC-TEG collaborative cooling systems are assessed in terms of power consumption, cooling capacity, coefficient of performance, and cooling efficiency. Compared with a typical Peltier cooling system, the two collaborative cooling systems achieve significant performance improvements.