Highly efficient excitation of LP_(01) mode in ring-core fibers by tapering for optimizing OAM generation

We have demonstrated the highly efficient excitation of the linearly polarized mode(LP01)in ring-core fibers(RCFs)by tapering the spliced point between the RCF and the standard single-mode fiber(SMF)to optimize all-fiber orbital angular momentum(OAM)generation.The tapering technique has been investigated theoretically and experimentally.Before tapering,only 50%of light can be coupled from SMFs to RCFs.The modal interference spectrum with an extinction ratio(ER)of～9 dB is observed,showing that higher-order modes are excited in RCF.By tapering the spliced point,90%of light is coupled,and the ER is minimized to be～2 dB,indicating that the higher-order modes are effectively suppressed by tapering.Such tapered spliced points of RCF–SMF are further applied for all-fiber OAM generation.The efficiencies of OAM+1 and OAM?1 generation are found to be enhanced by approximately 11.66%and 12.41%,respectively,showing that the tapered spliced point of the RCF–SMF is a feasible way to optimize OAM generation.     

保偏光纤的应力双折射与结构优化

简单介绍了保偏光纤的应力双折射,并着重介绍了应用有限元法对"一"字型与熊猫型结构保偏光纤的应力双折射的对比分析.分析结果表明,对"一"字型而言,纤芯区的双折射在一定范围内随应力区的长度及宽度加大而增大;在相同剖面结构参数条件下,"一"字型光纤应力区对双折射的贡献约为熊猫型光纤的1.3倍;无论是何种结构的保偏光纤,缩小应力区与纤芯之间的距离是增大纤芯区双折射更为有效的途径.同时对保偏光纤结构优化的趋势进行了展望.     

飞秒激光制备的全单模光纤法布里-珀罗干涉高温传感器

提出了一种全单模光纤的本征型法布里-珀罗干涉(IFPI)高温传感器。光纤IFPI传感器由飞秒激光在标准单模光纤上刻写的一对内部反射镜和腔内光纤构成,其反射光谱的干涉条纹对比度达到10dB,而插入损耗仅为0.1dB。实验结果表明,该传感器的测量温度可达1000℃,温度灵敏度为14.9pm/℃。而且在重复测量中,反射光谱具有良好的一致性,可以准确地实现高温传感。飞秒激光制备的光纤IFPI高温传感器完全由标准单模光纤构成,结构简单、成本低廉,易于连接现有的光纤器件构成光纤传感网络,在实际工程中有较大的应用价值。     

光纤材料锗缺氧中心与环结构特性研究

利用密度泛函理论(DFT)研究光纤材料中锗缺氧中 心(Ge-DDC)与环 结构特性,建立基于三环结构的Si-O-Si结构模型和Ge-ODC模型;同时,通过紫外可见光 (UV-Vis)吸收与拉曼测试分析研究光纤材料的微结构 特性。理论分析结果表明:对于未掺杂Ge的光纤材料,其带隙为8.36eV左右;而对于掺杂Ge元素的光纤材料,其带隙为 5.0eV左右,会在242nm波长处形成一个吸收 中心,并且它与Ge-ODC缺陷中心的吸收中心相 对应。在Ge-ODC缺陷结构中,其三环 Si-O-Si结构与Ge原子之间存在紧密联系。当掺Ge的光纤材料经辐照处理后,光纤材料中 容易产生GeE′和SiE′缺陷中心。光纤材 料受到不同剂量辐照后,光纤材料中的三环结构数量随着剂量的增加而减少。研究结果表明 ,石英材料中Ge-ODC缺陷结构容易产生 于环结构周围,并容易受到外界能量的影响。Ge-ODC与环结构特性的理论研究,对 超低损耗石英光纤的制备与设计具有重要的实际应用意义。     

细径熊猫型PMF的特性研究

应用于高精度光纤陀螺的细径熊猫型光纤属于应力致偏型保偏光纤(PMF).对工作波长为1 550nm的细径PMF的特性与研制过程进行了详细的阐述.所制备出的拍长为3.2 mm、消光比为26 dB(1 km)、低衰减、高强度且温度特性稳定的实用型细径熊猫型PMF为开拓国内高精度光纤陀螺及相关的光纤传感器件的工程化应用奠定了重...     

倾斜锥形微透镜单模光纤激发高阶涡旋光模式

提出了一种在环形芯光纤中激发高阶涡旋光模式的方法,通过控制锥形微透镜单模光纤与环形芯光纤之间的倾斜角度和错位距离,实现了高阶涡旋光模式的激发。由数值模拟与实验测试结果可知,倾斜角度和错位距离分别约为8°和2μm时,高质量的二阶涡旋光模式被激发。此外,由于锥形微透镜光纤具有聚焦光束的特性,其倾斜错位激发可以提高光的耦合效率,该方法与使用普通单模光纤的错位激发法相比,光的耦合效率提高13%左右。激发出的高阶涡旋光模式在高分辨率显微镜、光学微观操纵和光学传感等应用领域中具有巨大的应用潜力。     

A tension insensitive PbS fiber temperature sensor based on Sagnac interferometer

In this paper, a tension insensitive PbS fiber temperature sensor based on Sagnac interferometer is proposed and demonstrated. The sensing mechanism of tension and temperature is analyzed. The relationships between the interference spectrum, temperature and tension are analyzed, respectively. The experimental temperature range is 36—70 °C. The experimental results show that the interference spectrum is red shifted, and its sensitivity is 53.89 pm/°C. In tension experiment, the tension range is 0—1 400 με. The experimental results show that there is no wavelength shift in the interference spectrum. The sensor is immune to tension cross-sensitivity compared with other sensors. It can be used for temperature testing in aerospace, chemistry and pharmacy.     

法拉第旋转镜对旋转光纤磁光性能测量的影响

为了解决随机线性双折射对光纤磁光特性测量的影响,采用旋转光纤（SF）结合法拉第旋转镜（FRM）的测量方法,研究了FRM对旋转光纤磁光特性测量的影响。首先,从理论方面研究旋转光纤与FRM的引入如何减小光纤中的随机线性双折射对磁光特性测量的影响,并搭建基于FRM的旋转光纤磁光特性测试系统。当光源波长为1310 nm时,FRM作用前的旋转光纤费尔德常数都比未旋转光纤的大,且旋转光纤的节距越短,费尔德常数越大。特别是旋转光纤的节距为1.0 mm时,其费尔德常数为0.8304 rad/（T·m）,比未旋转光纤的费尔德常数[0.8029 rad/（T·m）]增大了约3.43%。当测试系统加入FRM后,不同光纤的费尔德常数测量值相较于未使用FRM的光纤费尔德常数测量值都有一定幅度的增大,尤其相比于节距为1.0 mm时的旋转光纤更进一步提高了7.50%,并且在FRM作用前后不同光纤费尔德常数测量值的均方差分别为0.99%和0.61%,说明FRM的引入提高了掺杂光纤费尔德常数的测量精度与稳定性。     

Fabrication and characteristics of character-1 shaped reduced diameter polarization-maintaining optical fiber

A novel structure reducing diameter polarization maintaining optical fiber with high birefringence and strength is introduced. The fiber is fabricated through using modified chemical vapor deposition (MCVD) method, which is able to produce the optimum predicted character-1 shaped fiber structure. As a result, a low-loss fiber with beat length close to 2.0 mm at 1310 nm wavelength and extinction ratio approximately -25 dB has been produced. The process is both simple and reproducible.