With the large-scale deployment of low earth orbit (LEO) satellite constellations, the demand for inter-satellite laser communication has grown significantly. Compared to traditional microwave communication, laser communication offers higher data transfer rates, greater capacity, and higher security. However, most existing laser communication systems are designed for point-to-point configurations, which are insufficient for the communication requirements of large-scale satellite networks. In particular, traditional point-to-point systems cannot efficiently interconnect multiple satellites in LEO constellations. In this paper, we propose a novel laser communication system to address challenges related to field-of-view (FOV) and long-distance communication in LEO satellite networks. By introducing a new laser communication system that supports multipoint communication, this approach facilitates the transition from point-to-point configurations to point-to-multipoint or multipoint-to-multipoint networking. The proposed system overcomes the limitations of narrow FOV and distance constraints inherent in traditional optical systems through advanced optical designs and system integration techniques.

To address the challenges of inter-satellite communication in LEO constellations, we first analyze satellite constellations and orbital configurations, detailing the relative positions and communication distances between satellites both within the same orbit and across different orbits. This orbital analysis is crucial for determining communication link characteristics and ensuring the optical system meets the required communication distances. Subsequently, a panoramic optical system is proposed, employing a dual-mirror configuration to achieve a wide FOV, which is essential for satellite network communication. The dual-mirror design significantly reduces optical aberrations compared to traditional block lens systems. Ray-tracing techniques and vector reflection laws are applied to analyze the interaction between light rays and the system’s optical components, linking outgoing rays to the desired FOV. Furthermore, a freeform mirror is designed and optimized using a point-by-point calculation method to derive its characteristic parameters, and an XY freeform surface is subsequently generated using fitting software. Finally, the freeform mirror is integrated with the rear mirror group, relay system, and collimation-coupling system to form a complete panoramic laser communication system. To verify the feasibility of the system, indoor equivalent validation experiments are conducted, simulating space losses through reduced transmission power, active attenuation, and decreased receive sensitivity to assess the system’s performance under real-world conditions.

In this paper, we propose a novel optical system tailored to the inter-satellite communication requirements of LEO satellite constellations. First, a panoramic optical system with a dual-mirror configuration is proposed, offering a significantly larger FOV than traditional Cassegrain optical systems (Fig. 14). This dual-mirror design effectively mitigates chromatic aberrations, thus enhancing communication link performance. Second, the integration of freeform mirror technology into the panoramic optical system further enhances light distribution and beam shaping, particularly at the FOV edges, effectively reducing optical aberrations and improving overall system performance. By optimizing the freeform mirror, the modulation transfer function (MTF) at the edges of the FOV is further improved, significantly enhancing image quality and reducing optical distortion by approximately 10%. Moreover, beam divergence is reduced by 60% compared to traditional aspheric systems, thus improving signal quality (Fig. 15). These innovations have been experimentally validated through indoor active attenuation experiments (Table 7), demonstrating the system’s long-distance communication performance. The combination of panoramic optical design and freeform mirror technology provides an innovative solution for future wide-field inter-satellite communication.

The proposed laser communication system successfully addresses the challenges of inter-satellite communication in LEO satellite constellations, meeting FOV requirements of 30°?70° and -30°?-70° with a maximum communication distance of 1200 km. Compared to traditional point-to-point communication systems, this design offers a wider FOV, enabling more flexible and efficient communication between satellites. The freeform mirror design further enhances image quality at FOV edges and reduces optical aberrations, which is critical for long-distance inter-satellite communication. Experimental results demonstrate that the system is capable of achieving a low bit error rate (BER) under simulated space-loss conditions, validating its feasibility for practical applications. Overall, the laser communication system proposed in this paper advances the development of point-to-multipoint and multipoint-to-multipoint systems, offering new possibilities for reliable and high-performance satellite communication networks and laying the foundation for future innovations in optical communication systems.