In optical wireless communication,undesirable channel is the main factor affecting system reliability,and placing an equalizer with opposite channel characteristics at the receiving end can offset the negative impact of the channel on the signal,so as to correct the inter-code crosstalk problem caused by multipath delay and other factors,and enable the signal to be recovered and reconstructed at the receiving end.On the basis of summarizing the research progress of equali-zation techniques both domestically and internationally,the article compares and summarizes various typical channel e-qualization techniques for reference,including zero forcing equalization,minimum-mean-square-error equalization,deci-sion feedback equalization,Volterra equalization,etc.In practical applications,appropriate equalizers can be selected based on specific requirements and equalization algorithm characteristics to achieve channel equalization.Finally,the de-velopment prospects of channel equalization technology in optical wireless communication are prospected,providing new i-deas and reference value for future researchers to explore in this field.
An optical fiber-type fluorescence sensor based on surface-enhanced fluorescence (SEF) is proposed and analyzed through the finite element method. The field enhancement property of the designed multimode SPR fiber is utilized to improve the excitation rate of fluorescent molecules, which improves the sensitivity of fluorescence detection. Because the gold film is too close to fluorescent biomolecules, which can lead to fluorescence quenching, an optically transparent layer is added between the surface of the gold nanofilm and fluorescent biomolecules. And then analyze the layer's material and thickness parameters. When the gold film and PDMS thicknesses are 50 nm and 60 nm, the field enhancement factor (T) reaches the maximum value of 9.45. This fluorescence enhancement method provides a design possibility for improving the fluorescence detection sensitivity.
We proposed a Raman and erbium-doped fiber amplifiers (EDFA) hybrid bidirectional optical amplifier (HBOA). The hybrid amplifier consists of a fiber Raman amplifier (FRA) and two EDFA, which are ingeniously combined by four WDMs. Gain and noise figure (NF) are the metrics used to evaluate the performance. The effects of Raman and EDFA pump on the gain and NF of the proposed hybrid amplifier are explored, resulting in a maximum gain exceeding 40 dB and an NF below 0 dB. Furthermore, when the input signal power is small (−35 dBm), the proposed hybrid amplifier, exhibits a total gain increased of ∼14 dB, and NF reduction of ∼4 dB across the wavelength span of 1545 to 1565 nm, as compared with EDFA-only. Finally, The Allan deviation can reach 1.41×10−14 when HBOA was used, significantly better than the stability of 2.62×10−14 obtained by Bi-EDFA, which confirmed the feasibility of the proposed amplifier for radio frequency synchronization systems.
在超快时间尺度上以二维空间分辨率揭示激光脉冲在光刻胶之间的运动过程,将有助于了解激光加工过程和优化加工工艺.然而现有记录激光脉冲在光刻胶中运动过程的成像技术都存在需要多次重复拍摄或时间分辨率受限等问题.为了克服这些问题,通过使用压缩超快摄影来观测光刻胶中激光脉冲的运动.实验结果表明,搭建的实验系统能以1.54×1011fps的帧率,单次成像数百帧的图像序列深度,实时观测到这一不可重复的超快事件.
针对普通卷积神经网络在遥感图像分割中林地边界区域识别不完整、小片林地分割精度低的问题,提出一种基于transformer与注意力机制的DeeplabV3+网络改进方法.在编码阶段引入transformer机制,将原池化金字塔部分中的空洞卷积操作替换为可获取更多上下文信息的transformer操作,从而提高网络对林地边界信息的提取能力;将注意力机制引入到网络的解码部分,提升模型对小片林地的检测能力.实验表明,采用改进后的方法平均交并比(MI-ou)可达到81.83％,对比原DeepLabV3+网络模型提升了1.25％.该方法充分考虑了卫星遥感图像分割中林地边缘信息的提取以及对小目标的关注度,提出的改进方法可提升遥感图像中对林地提取的精度.
