基于無波前探測的大氣光通信自適應(yīng)補償方法研究
發(fā)布時間：2019-04-09 20:08
【摘要】：自由空間光通信(FSO)由于通信容量大、速率高、保密性強等優(yōu)勢成為通信領(lǐng)域的研究熱點和前沿。FSO是以激光為載體在大氣信道中進(jìn)行信息的傳遞,因而會受到大氣湍流的影響。為了減小大氣湍流引起的通信性能的降低,開展大氣湍流下FSO系統(tǒng)的自適應(yīng)光學(xué)補償方法研究,對FSO系統(tǒng)性能改善與提高具有理論意義和實用價值。本文在自適應(yīng)光學(xué)原理、湍流中激光傳輸特性研究基礎(chǔ)上開展了基于無波前探測的自適應(yīng)光學(xué)原理對FSO系統(tǒng)通信性能的改善研究。探討了無波前探測的自適應(yīng)光學(xué)工作原理及系統(tǒng)模型,重點討論了差分進(jìn)化(DE)、隨機并行梯度下降(SPGD)和模擬退火(SA)算法應(yīng)用原理,通過對不同均方根相位的校正,驗證了三種算法對畸變波前校正均具有良好的效果。分析了大氣信道對激光傳輸特性的影響,利用Zernike多項式展開法和功率譜反演法產(chǎn)生了Kolmogorov譜下不同強度的大氣湍流相位屏,并對經(jīng)過湍流傳輸后的光束遠(yuǎn)場光強分布進(jìn)行了仿真計算。由于無波前探測的自適應(yīng)光學(xué)無需波前探測且不受光強閃爍效應(yīng)的限制,將該原理應(yīng)用于FSO系統(tǒng)對湍流引起的光束波前畸變進(jìn)行補償,數(shù)值模擬了基于DE、SPGD和SA算法的無波前探測自適應(yīng)光學(xué)原理在FSO系統(tǒng)中的應(yīng)用過程。分別討論了DE、SPGD和SA算法中各參數(shù)對算法收斂速度及收斂極值的影響,根據(jù)校正后光束斯特列爾比的變化規(guī)律給出了參數(shù)合適的取值范圍。將三種算法參數(shù)調(diào)至合適數(shù)值后,在得出不同湍流強度下無波前探測自適應(yīng)光學(xué)應(yīng)用前后接收端光功率基礎(chǔ)上,對比分析了系統(tǒng)誤碼率及光強閃爍指數(shù)的變化。結(jié)果表明:基于三種優(yōu)化算法的無波前探測自適應(yīng)光學(xué)原理都可增加FSO系統(tǒng)接收端光功率,進(jìn)而提高系統(tǒng)耦合效率及信噪比,在與理想光強比值為0.008的噪聲環(huán)境下,系統(tǒng)誤碼率可降低至610?以下,但對由小尺度湍流引起的光強閃爍效應(yīng)未能起到改善效果。通過對三種算法在運行速度、校正效果上進(jìn)行比較,發(fā)現(xiàn)DE算法在強湍流下校正效果最優(yōu),但需要的迭代次數(shù)最多,在較強湍流影響下SA比SPGD算法校正效果好,所需迭代次數(shù)比SPGD算法多。因此在實際應(yīng)用中,應(yīng)綜合系統(tǒng)在收斂速度、校正效果等方面的需求選擇合適的算法進(jìn)行性能優(yōu)化。
[Abstract]:Free space optical communication (FSO) has become a research hotspot and frontier in the field of communication due to its advantages such as large communication capacity, high speed and strong confidentiality, etc. FSO is the transmission of information in the atmospheric channel using laser as the carrier. Therefore, it will be affected by atmospheric turbulence. In order to reduce the communication performance degradation caused by atmospheric turbulence, the study of adaptive optical compensation for FSO system under atmospheric turbulence is of theoretical significance and practical value for improving and improving the performance of FSO system. In this paper, based on the principle of adaptive optics and the study of laser propagation characteristics in turbulence, the improvement of communication performance of FSO system based on adaptive optics principle without wavefront detection is studied. The principle and system model of adaptive optics for wavefront detection are discussed. The application principles of differential evolution (DE), random parallel gradient descent (SPGD) and simulated annealing (SA) algorithm are discussed. The results show that the three algorithms have good effects on distortion wavefront correction. The influence of atmospheric channel on the propagation characteristics of laser is analyzed. The atmospheric turbulent phase screens with different intensity under the Kolmogorov spectrum are generated by using the Zernike polynomial expansion method and the power spectrum inversion method. The far-field intensity distribution of the beam after turbulent propagation is simulated. Because the adaptive optics without wavefront detection does not need wavefront detection and is not limited by the flicker effect of light intensity, the principle is applied to compensate the wavefront distortion caused by turbulence in FSO system, and the numerical simulation based on DE, is presented. The principle of adaptive optics without wavefront detection based on SPGD and SA algorithm and its application in FSO system. The effects of the parameters in DE,SPGD and SA algorithms on the convergence rate and convergence extremum of the algorithm are discussed, and the appropriate range of parameters is given according to the variation rule of beam Steeler's ratio after correction. After adjusting the parameters of the three algorithms to the appropriate values, the optical power at the receiver end before and after the application of adaptive optics without wavefront detection under different turbulence intensities is obtained, and the changes of the bit error rate (BER) and the intensity scintillation index of the system are compared and analyzed. The results show that the principle of adaptive optics without wavefront detection based on the three optimization algorithms can increase the optical power at the receiving end of the FSO system, and then improve the coupling efficiency and the signal-to-noise ratio of the system. In the noise environment with a ratio of 0.008 to the ideal light intensity, the optical output of the system is improved. Can the BER of the system be reduced to 610? Below, the effect of light intensity scintillation caused by small-scale turbulence has not been improved. By comparing the operation speed and correction effect of the three algorithms, it is found that the DE algorithm has the best correction effect under strong turbulence, but it needs the most iterations. Under the strong turbulence influence, SA is better than the SPGD algorithm in the correction effect, and the correction effect of the SA algorithm is better than that of the SPGD algorithm under the influence of strong turbulence. The number of iterations required is more than that of SPGD algorithm. Therefore, in practical application, it is necessary to select the appropriate algorithm to optimize the performance of the system in terms of convergence rate, correction effect and so on.
【學(xué)位授予單位】：西安電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TN929.1
本文編號：2455496
[Abstract]:Free space optical communication (FSO) has become a research hotspot and frontier in the field of communication due to its advantages such as large communication capacity, high speed and strong confidentiality, etc. FSO is the transmission of information in the atmospheric channel using laser as the carrier. Therefore, it will be affected by atmospheric turbulence. In order to reduce the communication performance degradation caused by atmospheric turbulence, the study of adaptive optical compensation for FSO system under atmospheric turbulence is of theoretical significance and practical value for improving and improving the performance of FSO system. In this paper, based on the principle of adaptive optics and the study of laser propagation characteristics in turbulence, the improvement of communication performance of FSO system based on adaptive optics principle without wavefront detection is studied. The principle and system model of adaptive optics for wavefront detection are discussed. The application principles of differential evolution (DE), random parallel gradient descent (SPGD) and simulated annealing (SA) algorithm are discussed. The results show that the three algorithms have good effects on distortion wavefront correction. The influence of atmospheric channel on the propagation characteristics of laser is analyzed. The atmospheric turbulent phase screens with different intensity under the Kolmogorov spectrum are generated by using the Zernike polynomial expansion method and the power spectrum inversion method. The far-field intensity distribution of the beam after turbulent propagation is simulated. Because the adaptive optics without wavefront detection does not need wavefront detection and is not limited by the flicker effect of light intensity, the principle is applied to compensate the wavefront distortion caused by turbulence in FSO system, and the numerical simulation based on DE, is presented. The principle of adaptive optics without wavefront detection based on SPGD and SA algorithm and its application in FSO system. The effects of the parameters in DE,SPGD and SA algorithms on the convergence rate and convergence extremum of the algorithm are discussed, and the appropriate range of parameters is given according to the variation rule of beam Steeler's ratio after correction. After adjusting the parameters of the three algorithms to the appropriate values, the optical power at the receiver end before and after the application of adaptive optics without wavefront detection under different turbulence intensities is obtained, and the changes of the bit error rate (BER) and the intensity scintillation index of the system are compared and analyzed. The results show that the principle of adaptive optics without wavefront detection based on the three optimization algorithms can increase the optical power at the receiving end of the FSO system, and then improve the coupling efficiency and the signal-to-noise ratio of the system. In the noise environment with a ratio of 0.008 to the ideal light intensity, the optical output of the system is improved. Can the BER of the system be reduced to 610? Below, the effect of light intensity scintillation caused by small-scale turbulence has not been improved. By comparing the operation speed and correction effect of the three algorithms, it is found that the DE algorithm has the best correction effect under strong turbulence, but it needs the most iterations. Under the strong turbulence influence, SA is better than the SPGD algorithm in the correction effect, and the correction effect of the SA algorithm is better than that of the SPGD algorithm under the influence of strong turbulence. The number of iterations required is more than that of SPGD algorithm. Therefore, in practical application, it is necessary to select the appropriate algorithm to optimize the performance of the system in terms of convergence rate, correction effect and so on.
【學(xué)位授予單位】：西安電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TN929.1
【參考文獻(xiàn)】
相關(guān)期刊論文 前1條
1 張建柱;張飛舟;吳毅;;大氣湍流隨機相屏模擬方法研究[J];強激光與粒子束;2012年10期
，本文編號：2455496
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