Simultaneous displacement measurement method of multiple targets based on laser self-mixing interference

In order to simultaneously measure the displacements of multiple targets, the laser self-mixing interference(SMI) measurement method based on variational mode decomposition(VMD) is proposed. The SMI signal containing the motion information of the external targets is detected by a photodiode. The VMD can non-recursively decompose the mixed SMI signal into SMI signals corresponding to different external targets. The displacement signals can be reconstructed by fringe counting method and interpolation method. The experimental results show that the displacement signals of different external targets can be reconstructed with half wavelength accuracy, which verifies the correctness and feasibility of this method. This method can improve the measurement efficiency, which offers an effective method for the multi-channel displacement measurement.     

Optical arbitrary waveform generation based on an array of tunable apodized waveguide Bragg gratings

A structure of optical arbitrary waveform generation (OAWG) based on an array of tunable apodized waveguide Bragg gratings (WBGs) is proposed. The WBGs array on lithium niobate (LN) consists of several apodized gratings, waveguides and electrodes deposited on both sides of gratings and waveguides. The properties of OAWG are analyzed using transfer matrix method. Due to the electro-optic effect of LN, the amplitude and phase of incident light source are controlled via adjusting the voltages on electrodes. Consequently, the optical pulses with different waveforms are obtained and the amplitude is linearly tuned. In addition, voltages compensating amplitude and phase distortion are demonstrated.     

含季铵离子液晶聚合物

详细讨论了带有铵离子的液晶聚合物的合成与性能,以及铵离子对聚合物液晶性能的影响。研究表明,液晶相温度的增加是由铵离子在聚合物链中浓度的增加而引起的。     

季膦萘磺酸盐离子液体与甲基膦酸二甲酯协同阻燃环氧树脂

合成了一种新型季膦萘磺酸盐室温离子液体[TBP]NS,利用傅里叶变换红外光谱(FTIR)和核磁共振波谱(1H NMR和31P NMR)确定了其结构,并将其与甲基膦酸二甲酯(DMMP)复配用于制备阻燃环氧树脂.阻燃性能测试结果表明,当在环氧树脂(EP)中加入质量分数为6%的[TBP]NS和4%的DMMP时,所得阻燃环氧树脂EP/4%[TBP]NS/6%DMMP的极限氧指数达到31.2%, UL-94垂直燃烧通过V-0级别.与纯环氧树脂相比,该阻燃环氧树脂的峰值热释放速率(PHRR)降低了59%,总热释放(THR)降低了43%,峰值CO释放速率(PCOP)降低了41%,残炭率升高了97%.[TBP]NS和DMMP在氧指数、垂直燃烧和锥形量热测试中均展现出优异的协同阻燃作用,并且表现出良好的炭化能力和降热效果.在力学性能方面,与单纯加入DMMP的环氧树脂相比,EP/4%[TBP]NS/6%DMMP的拉伸强度、断裂伸长率和弯曲强度均有提高.     

FPI在光纤复用通信系统中的应用

本文介绍了光纤复用系统（ＷＤＭ和ＦＤＭ）中的几种基于Ｆａｂｒｙ一Ｐｅｒｏｔ干涉仪（ＦＰＩ）原理的波长选择器件,并对其测量范围、测量精度等主要特点进行了简单的分析．     

12例甲状腺癌误诊教训

分析讨论了１２例甲状腺癌误诊的教训。     

Fabrication and characterization of annealed proton exchanged long period waveguide grating in x-cut LiNbO3

In this paper, a long-period waveguide grating was fabricated in x-cut lithium niobate substrate by patterned annealed proton exchange waveguide fabrication process. The waveguide mode characteristic was evaluated using a charge-coupled device (CCD) camera. It shows that the waveguide is single mode transmission at a wavelength of 1 550 nm. The transmission spectra of the long period waveguide gratings were measured by optical spectrum analyzer (OSA) and show an extinction ratio of ~17 dB and a 3 dB bandwidth of ~10 nm at the resonant wavelength. The resonant wavelength moves toward to the long wavelength direction as the waveguide width-difference increases in the same period, and also shifts toward to the long wavelength direction with the increase of the period in the case of the same waveguide width-difference. The method of fabricating a long period waveguide grating based on a patterned annealed proton exchange technique simplifies the fabrication process, and at the same time, reduces the fabrication cost.     

基于基频混频的相位生成载波解调方法研究与改进

对基频混频相位生成载波解调方法的局限性进行了研究与改进.在该方法的基础上,通过引入直流滤波器,滤除了直流成分的影响,使得改进后的算法克服了基频混频相位生成载波解调方法只适用于小信号的局限性;通过引入抗混叠滤波器,保留了有用频谱成分,进一步降低了采样频率.在采样频率一定时,最大限度地提高了系统可解调的动态范围上限,给出了实现改进后算法的硬件实现方案,并用Matlab及数字信号处理器软件开发代码调试器分别进行了仿真验证,证明了这种改进解调方案的可行性.     

A band-pass microwave photonic filter based on Lyot-Sagnac filter and cascaded optical structures

A band-pass microwave photonic filter（MPF）based on Lyot-Sagnac filter and two cascaded optical structures is demonstrated.In the experiment,a stabilized and tunable multi-wavelength optical source is obtained by slicing the broadband optical source（BOS）with a Lyot-Sagnac filter.A standard single-mode fiber（SMF）and a fiber ring resonator are cascaded to improve the mainlobe-to-sidelobe suppression ratio（MSSR）and Q-factor of the filter.The analysis shows that MSSR and Q-factor are improved by reducing the split ratio of the coupler or increasing the length of fiber in fiber ring resonator.The results have significant guidance for MPF design by choosing appropriate devices and parameters.Based on the analyses,a band-pass filter with MSSR of 53.54 dB and Q-factor of 4048 is achieved by choosing the split ratio of0.01,the length of SMF of 30 km and the length of fiber in fiber ring resonator of 152.27 cm.     

Tunable modulation format conversion based on spectral line-by-line pulse shaper for all-optical signal processing

A tunable modulation format converter based on spectral line-by-line pulse shaper is proposed to realize different format conversions. The pulse shaper works as a format converter by setting its frequency response equivalent to the transform function between two formats. The working principles show that the format converter is suitable for different formats by adjusting its frequency response. Examples of format conversion from return to zero differential phase-shift keying （RZ-DPSK） to on-off keying （OOK） with different data packets and from return to zero （RZ） to non-return to zero （NRZ） are given. The results show that the format converter is not only suitable for different formats but also for random data packets.