The superposition of basic non-diffracting beams triggered new research hotspots lately,laying opportunities for long-distance wireless optical communication.The Lommel-Gaussian(LMG)beam formed by the superposition of...The superposition of basic non-diffracting beams triggered new research hotspots lately,laying opportunities for long-distance wireless optical communication.The Lommel-Gaussian(LMG)beam formed by the superposition of Bessel-Gaussian light not only possesses non-diffraction feature,but also has tunable symmetry.With the help of Poynting vector analysis,we observed a smaller radial energy flow component during the propagation of the high order symmetrical LMG beam,which allows it to maintain the original beam profile over long distance.Thanks to the energy oscillation of the mainlobe and sidelobes,the mainlobe blocked by the symmetrical LMG beam can be restored.Also,the random phase screen with angular spectrum method is used to describe the beam behaviors in turbulence.The results show that the symmetry LMG is preferred in free space optical communication,and the asymmetric LMG performs poorly due to asymmetric energy transfer.展开更多
为解决有记忆非线性的连续相位调制(CPM)信号调制方式识别精度低的问题,该文提出一种基于记忆因子的CPM信号最大似然调制识别新方法。该方法定义具有时齐马尔科夫性的映射符号,通过计算其后验概率构造记忆因子,进一步结合CPM分解和EM算...为解决有记忆非线性的连续相位调制(CPM)信号调制方式识别精度低的问题,该文提出一种基于记忆因子的CPM信号最大似然调制识别新方法。该方法定义具有时齐马尔科夫性的映射符号,通过计算其后验概率构造记忆因子,进一步结合CPM分解和EM算法,推导出时间可分离,信道参数可估计的CPM信号似然函数。该调制识别方法所需符号数目少,适用信噪比范围广,识别CPM信号种类多且精度高,对相位误差鲁棒性强。仿真结果证明,当符号数目为200,信噪比为0 d B,相位误差任意时,该方法对8种CPM信号的识别率可达95%以上。展开更多
This Letter introduces a trigger-controlled Geiger-mode avalanche photodiode （GM-APD）. A hierarchical look- back-upon tree recurrence method is given to predict the performance of trigger-controlled GM-APDs under di...This Letter introduces a trigger-controlled Geiger-mode avalanche photodiode （GM-APD）. A hierarchical look- back-upon tree recurrence method is given to predict the performance of trigger-controlled GM-APDs under different trigger-count upper limits. In addition, the normalized detection probability is defined to evaluate the detection performance of trigger-controlled GM-APDs in typical weak optical signal detection （impulse noise and continuous noise situations）. Theoretical analyses show that the trigger-controlled GM-APD improves the detection performance of GM-APDs in weak optical signal detection via the optimization of the trigger-count upper limit, compared with single-trigger and multi-trigger GM-APDs.展开更多
基金supported by the National Key R&D Program of China(No.2018YFB1802302)the National Natural Science Foundation of China(Nos.11774181,61727815,11274182,11904180,11804250 and 1190426)+2 种基金the Natural Science Foundation of Tianjin(Nos.19JCYBJC16700 and 20JCQNJC01480)the Science and Technology Project of Tianjin(No.20YDTPJC00760)the Tianjin Development Program for Innovation and Entrepreneurship。
文摘The superposition of basic non-diffracting beams triggered new research hotspots lately,laying opportunities for long-distance wireless optical communication.The Lommel-Gaussian(LMG)beam formed by the superposition of Bessel-Gaussian light not only possesses non-diffraction feature,but also has tunable symmetry.With the help of Poynting vector analysis,we observed a smaller radial energy flow component during the propagation of the high order symmetrical LMG beam,which allows it to maintain the original beam profile over long distance.Thanks to the energy oscillation of the mainlobe and sidelobes,the mainlobe blocked by the symmetrical LMG beam can be restored.Also,the random phase screen with angular spectrum method is used to describe the beam behaviors in turbulence.The results show that the symmetry LMG is preferred in free space optical communication,and the asymmetric LMG performs poorly due to asymmetric energy transfer.
文摘为解决有记忆非线性的连续相位调制(CPM)信号调制方式识别精度低的问题,该文提出一种基于记忆因子的CPM信号最大似然调制识别新方法。该方法定义具有时齐马尔科夫性的映射符号,通过计算其后验概率构造记忆因子,进一步结合CPM分解和EM算法,推导出时间可分离,信道参数可估计的CPM信号似然函数。该调制识别方法所需符号数目少,适用信噪比范围广,识别CPM信号种类多且精度高,对相位误差鲁棒性强。仿真结果证明,当符号数目为200,信噪比为0 d B,相位误差任意时,该方法对8种CPM信号的识别率可达95%以上。
文摘This Letter introduces a trigger-controlled Geiger-mode avalanche photodiode （GM-APD）. A hierarchical look- back-upon tree recurrence method is given to predict the performance of trigger-controlled GM-APDs under different trigger-count upper limits. In addition, the normalized detection probability is defined to evaluate the detection performance of trigger-controlled GM-APDs in typical weak optical signal detection （impulse noise and continuous noise situations）. Theoretical analyses show that the trigger-controlled GM-APD improves the detection performance of GM-APDs in weak optical signal detection via the optimization of the trigger-count upper limit, compared with single-trigger and multi-trigger GM-APDs.
