With the increasing demand on the data rate of high definition (HD) remote detection using unmanned aerial vehicles (UAVs), scientists have moved on from the technique of traditional microwave communication to the technique of optical communication. Through transmitting data to a geosynchronous orbit relay satellite at a high data rate, a UAV can release the storage capacity of its hard drive so as to immediately conduct a new round of HD photo shooting. In this case, we construct a theoretical model of a UAV-to-satellite optical communication system. To optimize the system performance, this paper analyzes the Doppler effect, the pointing error effect, and the atmospheric turbulence effect on the communication performance based on a theoretical study and numerical simulations. In terms of the Doppler effect, the extra background noise caused by slightly increasing the optical filter bandwidth at the receiver has a far weaker effect on the communication performance compared with the effects of atmospheric turbulence and pointing error. In terms of the effects of atmospheric turbulence and pointing error, we further analyze the key parameters of both uplink and downlink systems to better understand these effects. The numerical results can provide data references for practical system designs.

To verify the feasibility of Brillouin optical time domain reflector (BOTDR) applied in space station, three kinds of commercial fibers, YOFC fiber (about 1km), Corning fiber (about 1km) and Fujikura fibers (about 1.5km), have been radiated by Co60 in radiation experiment. Based on the Brillouin Gain Spectrum (BGS) along sensing fiber, we analyze power curve of Brillouin backscattered light, Brillouin Frequency Shift (BFS) along sensing fiber and spatial resolution carefully. The results indicate that radiation has little effect on BFS when signal-to-noise ratio (SNR) is large enough. However, since radiation will lead to radiation-induced attenuation, the amplitude of BGS will decrease accordingly. And if the SNR becomes small enough, the accurate BFS cannot be obtained. For the stressed fiber section of BOTDR, the result shows that radiation has little effect on the strain coefficient at the total radiation dose of 200Gy, but radiation will deteriorate the spatial resolution of BOTDR with the increase of radiation dose. These results are good references for the introduction of BOTDR to space station.

Hybrid free space optical (FSO)/radio frequency (RF) systems have been proved to be reliable links for high-data-rate wireless backhauls. In this paper, we present a unified performance analysis of the hybrid FSO/RF transmission system which transmits the identical data in both links and implements two popular diversity combining schemes, namely, selection combining (SC) and maximal ratio combining (MRC), in the receiver. Specially, for the FSO link, the Gamma-Gamma turbulence with pointing errors under heterodyne detection (HD) and intensity modulation/direction detection (IM/DD) is considered in our analysis while the general - shadowed fading which unifies popular RF fading models is employed for the analysis of the RF link. As a result, unified closed-form expressions of outage probabilities and average bit error rates for different modulation schemes are derived. Analytical and Monte Carlo simulation results are provided to characterize the performance of the hybrid FSO/RF link which is compared to the single FSO link and the single RF link. The agreement between the analytical and simulation results confirms the unification of various FSO channels and RF fading scenarios into a single closed-form expression.

Minimum shift keying (MSK) has been widely used in fiber optical communication and free-space optical communication. In order to introduce MSK into satellite laser communication, the bit-error rate (BER) performance of the MSK scheme is investigated in uplink communications under the influence of atmospheric turbulence consisting of weak fluctuation and beam wander. Numerical results indicate that the BER performance of MSK is much better than the performance of on–off keying (OOK). With the laser power being 4 W, the improvement is 5 dB in coherent demodulation and 15 dB in delay coherent demodulation. Furthermore, compared with OOK, optimal values of the divergence angle, receiver diameter, and transmitter beam radius are easier and more practical to achieve in the MSK scheme. The work can benefit ground-to-satellite laser uplink communication system design.

In a ground-to-satellite communication system with a preset EDFA, the EDFA’s performance will be affected by space environment. With 250 Gy radiation, the EDFA’s gain decreases by 2 dB from 19.97 dB at $20°\text{C}$. The BER increases by 2.5 orders of magnitude from 10⁻¹⁰, and increases more with more radiation. The situation aggravates when the temperature rises by $73°\text{C}$. The laser’s divergence-angle and transmitter radius have optimal values to make the lowest BER and increasing receiver diameter makes lower BERs, so setting these parameters with appropriate values will compensate the degradation caused by EDFA.

Chaotic modulation is a scheme used to enhance the information security through the configuration parameter synchronization. When chaotic modulation is adopted in the space-to-ground laser communication system, the traditional bit error rate (BER) calculation model for fiber-based chaos communication system is no longer available to depict the long-term communication performance. To solve this problem, we established a new ensemble average BER calculation model under the effects of intensity scintillation and pointing error. Based on this model, we conduct a simulation to research such a system, and our numerical results indicate that space-to-ground chaos laser communication system has a great anti-interference against these two effects when the detector mismatch approaches zero. Our results display the advantages of chaotic modulation and also reflect the characteristics of space-to-ground chaos laser communication system.