Investigation of the Doppler Frequency Shift Effect on Inter-Channel Switching Time of Free-space Optically Switched Communication Networks with Distributed Feedback Laser Array Technique

Abstract

To assess the impact of Doppler frequency shift and channel crosstalk on the performance of a four-channel free-space optically switched communication network, particularly in scenarios involving low Earth orbit satellites, we derived a bit error rate model under the influence of satellite-ground Doppler frequency shift and channel crosstalk in atmospheric turbulence. This model focuses on studying a four-channel distributed feedback (DFB) laser array through numerical simulation. We initially analyzed the effect of crosstalk on the system's switching time in the absence of Doppler frequency shift. Our research revealed that as the channel spacing increased, the impact of crosstalk on the system's optical switching time decreased. We utilized a primary power compensation solution, adjusting the output optical power for different channel spacings, to mitigate the influence of crosstalk on the system's switching time. After eliminating the effects of crosstalk, we further examined the impact of Doppler frequency shift on the system's switching time for different channel spacings. We proposed a secondary power compensation solution to mitigate the effects of both crosstalk and Doppler frequency shift on the system's switching time. Finally, through simulation experiments, we set the output optical power of the laser to 10.42mw when switching from channel 1 to channel 2, 9.05mw when switching from channel 1 to channel 3, and 8.68mw when switching from channel 1 to channel 4, ensuring a uniform switching time of 10ns. Our research results provide a solid theoretical foundation for enhancing the performance of free-space optically switched communication networks and for mitigating the impact of Doppler frequency shift on system switching time.