We propose a new free-space optical (FSO) communication system for moving platform tracking, which can achieve high precision aiming and tracking. Our prototype system consists of three parts. As a coarse sighting structure, the electro-optical pod module is used for target searching and coarse sighting in the initial stage. As a precise aiming structure, the precise targeting loads module located inside the electro-optical pod module uses miniaturized tubular folding optical path technology for high-precision alignment and tracking. The bottom module of the system is used for communication. In the tracking process, the control unit uses spot offset collected by CCD to perform decoupling calculation and then compensates the offset by swinging tracking and aiming structure. We did track experiments on a mobile platform. The experiment successfully tracked a moving target at 100 m distance, and the tracking error was less than 1 mrad. The proposed system can provide stable communication links between the mobile platforms.

Ultraviolet (UV) communication is considered an effective complement to traditional wireless communication. However, the scattering models of existing non-line-of-sight (NLOS) UV, which are complex, are difficult to combine with the test. In this paper, the single scattering isosceles model with a small elevation angle is proposed first. Then, the relationships between the path loss of single scattering isosceles and elevation angle, emission beam angle, receiving field angle, and transmission distance are studied. Finally, we consider outdoor NLOS UV solar-blind communications test at ranges of up to 100 m and 400 m, with different transmit and receive elevation angles. The results show that the isosceles model is in good agreement with the experiments. In addition, the UV isosceles model exhibits good properties compared with the existing scattering model. The proposed UV isosceles model can be employed as a reference for practical applications in outdoor tests.

This paper presents a miniaturized equipment used in tracking and pointing, and provides a method for free space optical communication among small platform. This scheme uses simple scan mirror and receiver with single photo detector to achieve tracking function. Signal beacon is controlled to rotate around target receiver. Transmitter constantly adjusts emitting direction to track receiver according to received signal intensity, which is send back by reverse laser link. The prototype system is successfully established and its transmitting part consisted by directly modulated laser diode, mechanical collimation lens, and scan mirror is also proved. The receiving end is mainly composed of large area photo detector and short-focal lens. Field-programmable gate array chips set in both ends are used to implement tracking algorithm. This system can track target at speed of 40 mm/s within 2 m distance in an angle range of ±30°. For further application, the system has great potential for miniaturization because of elimination of motors, beacons and cameras in its scheme.

In ultraviolet (UV) communication, On–Off Keying (OOK) is the primary modulation technique. Compared to OOK, frequency modulation offers stronger resistance to path attenuation. Currently, research on frequency modulation demodulation schemes for UV communication is limited, mainly employing waveform detection and laser pulse response methods, which require high detection sensitivity to light. This study presents a novel frequency modulation communication scheme using discrete Poisson channel distribution and optical pulse signal processing algorithms, enhancing the signal processing sensitivity of the existing frequency modulation scheme to the level of photons. The proposed system model is rigorously evaluated through theoretical derivations and simulations. Additionally, a hardware system integrating optical pulse counting, frequency detection, and clock data recovery algorithms is developed. Experimental results show the system achieving a 5 kbps transmission rate under frequency modulation. In non-line-of-sight (NLOS) scenarios, communication reaches up to 65 m, with the receiver elevation angle ranging from 10° to 25° and the bit error rate (BER) stabilized at 10⁻⁴, while in line-of-sight (LOS) situations, the BER remains at 10⁻⁵ up to 400 m and 10⁻⁴ up to 700 m, achieving the farthest distance and fastest communication rate achievable in the current FSK modulation scheme of ultraviolet communication systems. The integrated components enhance its applicability in communication systems. This study offers a valuable addition to UV communication technology.

This paper proposes a rotation-locking alignment scheme and system based on a Gaussian beam addressing the relative displacement between the receiver and the spot center during the fine tracking phase of spaceborne laser communication APT technology caused by platform vibration, temperature variations and other factors. By rotational scanning fitting, the offset angle and offset distance of the receiver relative to the spot center can be derived and achieve high-precision adaptive tracking. The simulated result demonstrates that the fitting distance error of this scheme is less than 1%, and the fitting angle error is less than π/32. At the same time, the system prototype is developed to conduct ground-based validation experiments, including the static test and outdoor link establishment test. The system prototype features simpler structure, lower computational complexity, and easier integration, satisfying the miniaturization and lightweight design requirements for spaceborne laser communication terminals. The test results verify the system can successfully establish stable laser communication links rapidly.