Performance analysis of 128-QAM-OFDM-based inter-satellite optical wireless communication link at 140 Gbps under pointing errors, additional losses, and link parameter variations

This paper presents a simulation-based performance analysis of a 140 Gbps inter-satellite optical wireless communication (IsOWC) link employing 128-QAM-OFDM modulation at an operating wavelength of 850 nm over a single optical channel. The proposed system incorporates channel estimation and carrier phase estimation (CPE) at the receiver to mitigate phase noise and enhance signal demodulation accuracy. System performance is characterized in terms of bit error rate (BER) and received optical power (ROP) across a range of critical link parameters. Specifically, the effects of pointing errors (1–2 μrad), additional link losses (5–10 dB), and transmit laser power (24–30 dB m) are evaluated at inter-satellite distances of 15,000, 20,000, and 25,000 km. Furthermore, the influence of receiver aperture diameter (10, 12, and 15 cm) and optical system efficiency (0.7–0.9) on link performance is investigated over propagation ranges spanning 12,000–30,000 km. Simulation results demonstrate that higher transmit power and larger receiver apertures yield substantial improvements in BER performance, while increased pointing errors and additional link losses impose significant penalties on link reliability. These findings provide quantitative design guidelines and practical operating boundaries for the development of high-capacity IsOWC systems in next-generation satellite communication networks.