多模光纤中存在的多个自由度为大容量通信和多参量传感提供了可能, 然而多模光纤中存在的高阶模不仅不稳定、 易耦合和易辐射损耗, 而且导致了布里渊增益谱畸变、 谱宽展宽和布里渊增益峰值降低, 严重劣化了系统的测量精度与传感可靠度。 因此, 研究多模光纤布里渊增益谱的特性和整形优化尤为重要。 首先对多模光纤的布里渊频移和布里渊增益谱特性进行了理论研究, 并与少模光纤、 单模光纤进行对比。 结果表明： 多模光纤的布里渊频移与模式折射率及布里渊散射角有关, 当布里渊散射角不变时, 布里渊频移与模式群编号呈负相关; 当模式群编号不变时, 布里渊频移与布里渊散射角呈正相关。 相比单模光纤, 少模光纤与多模光纤由于受到高阶模的影响, 布里渊增益峰值和布里渊频移较低, 布里渊增益谱较宽。 多模光纤中的高阶模最多, 对应的布里渊增益峰值和布里渊频移最低, 布里渊增益谱最宽。 此外, 分析并设计了两种基于单模光纤的多模光纤布里渊增益谱整形优化方法。 搭建移频本地外差布里渊光时域反射系统, 通过测量比较两种整形优化系统的布里渊增益谱宽及抗弯曲性能, 以评估整形优化程度。 实验结果表明： 提出的两种整形优化方法不同程度地减小了多模光纤的布里渊增益谱宽, 获取的布里渊增益谱有着良好的Lorenz拟合度, 分别为0.974 47和0.987 89。 利用单模环形器结合单模光纤对准熔接多模光纤的方法有更好的整形优化效果和抗弯曲性能, 最小弯曲半径和布里渊增益谱宽分别为2.25 mm和53.12 MHz。

结合五矿矿业安徽李楼铁矿-425 m中段矿柱爆破回采工程实例，利用应力波理论，分析了爆炸应力波在全尾砂胶结充填体中的传播及其与介质界面的相互作用，基于充填体的冲击压剪、剪切和反射拉伸等不同破坏机制和破坏准则，研究了充填体的质点振动速度阈值。研究表明：在爆炸应力波作用下，矿柱与1∶8充填体的胶结面易发生剪切破坏，而胶结充填体易发生压剪破坏; 在透、反射应力波作用下，1∶8和1∶20配比充填体的胶结面易发生拉裂破坏，而与1∶20充填体相邻侧的1∶8充填体则可能发生层裂破坏。具体的充填体质点振动速度阈值为：矿柱与1∶8充填体胶结面的剪切破坏质点振速阈值为27.6 cm/s，紧邻矿柱1∶8充填体的冲击压剪破坏质点振速阈值为172 cm/s; 1∶8和1∶20配比充填体胶结面的拉裂破坏质点振速阈值为12.6 cm/s，而与1∶20充填体相邻侧1∶8充填体的层裂破坏质点振速阈值为52.6 cm/s。

Based on the density functional theory with hybrid functional approach, we calculated the structural, electronic, and the optical properties of Cu₂MgSn(S_1-xSe_x)₄ (CMTSSe)，an potential photovoltaic material for thin film solar cells. The calculation reveals a phase transition from kesterite to stannite structure when Zn atoms are substituted by Mg atoms. In particular, the S-to-Se ratio can determine the energy splitting between the electronic states at the top of the valence band. The band gaps of CMTSSe can be tuned in the ranges of 1.01—1.58 eV. Calculated optical properties and tunable band gaps make them beneficial for achieving band-gap-graded solar cells.

Cu2ZnSnSe4 (CZTSe) absorbers were deposited on borosilicate glass substrate using the low-temperature process, and different Na incorporation methods were applied to investigate the effects of Na on the CZTSe growth. Na was dif-fused into some of the absorbers after growth, which led to strongly improved device performance compared with Na-free cells. With the post-deposition treatment, the effect of Na on CZTSe growth was excluded, and most of Na was expected to reside at grain boundaries. The conversion efficiency of the completed device was improved due to the enhancement of open circuit voltage and fill factor. The efficiency of 2.85% was achieved at substrate temperature as low as 420 ℃.

The self-heterodyne detection Brillouin optical time domain reflectometer (BOTDR) system using broad-band laser is proposed to reduce coherent Rayleigh noise and improve the system performance. Compared with the system with narrow-band laser, the stimulated Brillouin scattering (SBS) threshold can be improved by about 3 dB. The experi-mental results of the narrow-band laser measurements for three times independently and the broad-band laser meas-urement for one time are compared. The root-mean-square (RMS) errors of Brillouin linewidth for two systems with narrow-band laser and broad-band laser are 6.9 MHz and 2.7 MHz, respectively, and the RMS errors of temperature for the heated fiber are about 1.3 °C and 0.7 °C. With the broad-band laser, signal-to-noise ratio (SNR) of the un-heated fiber is approximately equivalent to that of the integrated three independent Brillouin signals for the narrow-band laser, and the results are believed to be beneficial for performance improvement and measurement time reduc-tion.

Aiming at the problem of large fading noise in Rayleigh Brillouin optical time domain analysis system, a wavelength scanning technique is proposed to enhance the performance of the temperature sensing system. The principle of the proposed technique to reduce the fading noise is introduced based on the analysis of Rayleigh Brillouin optical time domain analysis system. The experimental results show that the signal-to-noise ratio (SNR) at the end of optical fiber with length of 50 m after 17 times wavelength scanning is 5.21 dB higher than that with single wavelength, the Brillouin frequency shift (BFS) on the heated fiber with length of 70 m inserted at the center of sensing fiber can be accurately measured as 0.19 MHz, which is equivalent to a measurement accuracy of 0.19 °C. It indicates that the proposed tech-nique can realize high-accuracy temperature measurement and has huge potential in the field of long-distance and high-accuracy sensing.

理论分析了瑞利BOTDA(布里渊光时域分析)传感系统的动态范围, 提出了一种采用脉冲编码技术改善系统信噪比从而增大系统动态范围的方法。研究了瑞利BOTDA系统中格雷码和Simplex码的编码和解码原理, 通过对瑞利BOTDA系统采用叠加平均法和脉冲编码法后信噪比改善量的分析对比, 阐明了脉冲编码技术在增大瑞利BOTDA系统动态范围方面的优越性, 并利用Matlab软件进行了仿真验证。仿真结果表明, 该编码技术能够明显改善系统信噪比, 增大系统的动态范围。

为了减小相干瑞利噪声, 提出了一种多波长瑞利和布里渊自外差检测布里渊光时域反射系统。分析了相位调制产生多波长探测光的机理及三波长系统的自外差检测原理; 搭建单波长和三波长自外差检测布里渊光时域反射系统, 获得了沿光纤的自外差信号功率和布里渊频移。实验结果表明, 相对于单波长系统, 三波长系统有效地减小了相干瑞利噪声引起的功率波动, 信噪比提高近4.56 dB; 布里渊频移波动的均方根误差降低2.2 MHz。

为简化系统结构、减小相干瑞利噪声对系统性能的影响, 提出了一种采用宽带光源的瑞利和布里渊散射自外差检测布里渊光时域反射温度传感系统.分析了瑞利和布里渊自外差检测原理, 研究了布里渊频移和自外差信号功率与光纤温度和应变的关系.设计并搭建采用宽带光源的自外差检测布里渊光时域反射温度传感系统, 获得了常温下沿光纤分布的自外差信号功率谱及不同温度时加温段光纤的功率谱, 验证了布里渊频移和自外差信号相对功率变化随温度的线性增加关系.通过实验数据获得的布里渊频移和相对功率变化的温度系数分别为1.07±0.01 MHz/℃和(0.37±0.09)%/℃.本文的研究结果为基于瑞利和布里渊自外差检测布里渊光时域反射传感系统的温度和应变同时测量提供了理论和实验依据.