缺陷型内包层双包层光纤吸收效率研究

缺陷型内包层双包层光纤由于其特殊的内包层横截面结构,对于光波的吸收效率要比理想圆型内包层双包层光纤提高许多.由于射线法在分析光波在光纤中的场分布、传播功率等情况时有其局限性,因此,文章改用波动理论对缺陷型内包层双包层光纤进行分析,试图找出不同类型的缺陷型内包层双包层光纤单位距离内吸收效率的差异.     

用边界反射原理计算双包层光纤的吸收效率

以双包层光纤(DCF)中内外包层分界面上的点作为研究对象,对于分界面上的任意一点运用边界反射原理,确定在内包层截面中,能发出被掺杂纤芯吸收的光线的点源所占有的面积,将此面积与内包层总截面积作一比较,算出这一点对双包层光纤吸收效率的贡献。按该方法计算内外包层分界面上每一点对吸收效率的贡献并取平均,最后可求得双包层光纤的总吸收效率。讨论了双包层光纤的圆对称和偏心两种情况,结果与已有文献中的结论完全一致,但这种方法的计算过程更为简便。     

双包层光纤侧面耦合器

研究了一种侧面抽运双包层光纤的方法,从被剥除了外包层、端面为350μm×400μm的D型双包层光纤内包层上切下长度为3mm的一段柱体,并胶合在相同的双包层光纤内包层的侧面上,构成了柱体-光纤侧面耦合器。半导体激光器的抽运光从该柱体的一端入射并通过它耦合进入双包层光纤的内包层,实验测得耦合器最大耦合效率为85%。该方法适用于输出功率为数瓦的光纤激光器和放大器的侧面抽运。     

弯曲双包层光纤吸收效率的理论分析

以耦合功率理论为基础,提出了一种分析弯曲结构双包层光纤吸收效率的新方法.在双包层光纤内,由于弯曲结构引起在内包层中传输的泵浦光发生模式间的耦合,通过分析居于主要地位的模式间发生耦合的情况,计算耦合功率的大小.然后根据此功率的大小,判断弯曲结构双包层光纤内掺杂纤芯吸收泵浦光功率能力的强弱,并通过计算实例,分析弯曲结构对吸收效率的影响.最后结合侧面泵浦耦合技术,提出了一种新的大功率双包层光纤激光器的设计模型.     

新型全光纤结构双包层光纤激光器

基于对双包层光纤的内包层结构、掺杂浓度、剖面折射率分布、外包层的背底损耗等因素对泵浦光吸收效率的影响进行分析的基础上,对掺Yb3 双包层光纤内包层直径对泵浦光的吸收长度和泵浦效率进行了理论模拟.采用半导体激光二极管光纤模块作为泵浦源,采用梅花瓣型双包层光纤与光纤光栅元件连接制作了全光纤结构的光纤激光器,实验获得了6.02W单模光纤激光器,中心波长为1080nm,半高宽为0.11nm,斜率效率为1.7W/A.     

高功率双包层掺铥光纤放大器温度分布特性

通过对普适于不同内包层边界条件下的热传导方程进行推导和求解,得到了不同内包层形状的双包层增益光纤所对应的掺铥光纤放大器的三维热分布。计算结果表明,双包层光纤不同内包层形状可导致纤芯处的温度差高达107 K。同时,信号光与泵浦光功率的比值决定了温度最高点和熔接点的距离,在泵浦光功率为100 W、信号光功率为10 mW的情况下,两者之间的距离可达30 cm。通过分析不同内包层形状的双包层光纤的径向与轴向的热分布情况发现,相较于其他内包层形状的双包层光纤,偏芯型双包层掺铥光纤因其具有较低的最高温度、较高的泵浦效率和高斯型横截面热分布而较适用于掺铥光纤放大器。     

双包层光纤吸收效率影响因素的研究

泵浦光的吸收效率是影响双包层光纤激光器输出功率的重要因素.在对双包层光纤的掺杂离子浓度、纤芯直径、内包层形状和尺寸、光纤弯曲和缠绕、外包层的背底损耗等因素对吸收效率的影响进行分析的基础上,分析了改变上述因素来提高吸收效率过程中,会出现的制约因素和需要注意的问题.     

双包层光纤内包层形状对吸收效率的影响分析

在理想情况下，用二维几何光学对双包层光纤中的泵浦光传输路线进行分析，从而得出不同内包层形状下的吸收效率。圆形内包层有最低的吸收效率，破坏同心圆的圆对称性后吸收效率显著提高，如偏心圆结构有比同心圆大的吸收效率，矩形和D形内包层可以达到理论上100％的吸收效率。     

双包层光纤芯径与位置影响吸收效率的研究

为了提高双包层光纤结构中泵浦光耦合进纤芯的效率,文章首先探索了常折射率内包层光纤中芯径与内包层尺寸比对吸收效率的影响.然后对端泵入射光进行建模,研究了纤芯偏心距的优化.数值模拟结果表明,当偏心距为R-r时,即纤芯位于内包层边缘时,吸收效率最高.文章还阐述了渐变折射率内包层对耦合效率的影响.     

CO2激光熔接型双包层光纤侧面抽运耦合器

为了把高功率的半导体激光器抽运光耦合入直径只有数百微米的双包层光纤内包层,以获得高的抽运功率,同时简化端面抛磨式熔接型侧面耦合器复杂的光纤处理工艺,提出了一种基于CO2激光熔接的双包层光纤侧面抽运耦合器的新方法,并进行了实验验证,介绍了试验装置和制作过程,制作了内包层直径为125μm非掺杂双包层光纤与105μm/125μm多模光纤的侧面耦合器,得到了82%的耦合效率测试结果。结果表明,所研制的熔接型侧面耦合器在侧面抽运的高功率双包层光纤激光器中具有很好的应用前景。     

Double Clad Er-doped Fiber Amplifier

Presented is a theoretical study of double-clad Er-doped fiber power amplifier（EDFA）. Two kinds of double clad fibers（DCF） with rectangular and ＂flower＂ inner clad shapes are studied, and these fibers have different coupling constants and propagation losses. We calculate the effective pump power absorption ratio along the fiber with different coupling constants from the first cladding to the doped core and with different propagation losses for the power in the inner cladding. Then the gains of the double clad Er-doped fiber amplifiers versus fiber lengths are calculated using the EDFA model based on propagation and rate equations of a homogeneous, two-level medium.     

D形双包层大模场光纤激光偏振特性研究

为了考察双包层光纤激光器的偏振行为,选用国产大模场D型内包层光纤,采用单端抽运的方法,测量了不同缠绕半径和不同抽运强度下光纤输出激光的偏振态。结果表明,激光器在阈值附近单波长运转时,如果光纤缠绕半径较小,输出激光表现出较明显的偏振特征,如果缠绕半径较大,输出激光偏振特征较弱;高于阈值多波长运转时,无论采用何种缠绕半径,都观测不到偏振现象。     

Multi-coupler side-pumped Yb-doped double-clad fiber laser

The side-coupler of angle polished method, using angle-polished multimode fiber and optical adhesive, is used to efficiently pump an Yb-doped double-clad fiber laser. The maximum coupling efficiency of 78.6%is achieved by the side-coupler for a multimode fiber with a circular core of 200 μm and a double-clad fiber with a 350/400 μm D-shaped inner cladding. While laser diodes (LDs) with three side-couplers are simultaneously used as pump sources, maximum output power of 1.38 W and slope efficiency of 48.9% are demonstrated in the fiber laser system.     

渐变折射率双包层光纤吸收效率的波动理论分析

用已知的积分公式计算了光纤中的总模数;用WKN方法推导了2个积分,分别用以计算两部分不能被双包层光纤(DCF)纤芯吸收的模式数量;最后将不被吸收的模式数与光纤总传播模式数作比较,得出渐变折射率DCF的吸收效率。给出了计算实例．讨论了吸收效率与渐变折射率参数及纤芯偏心距离之间的关系。     

Analysis of Ultra-Broadband Amplified Spontaneous Emissions Generated by ${rm Cr}^{4+}{:}{rm YAG}$ Single and Glass-Clad Crystal Fibers

Numerical analysis and experimental verification of the ultra-broadband amplified spontaneous emissions (ASEs) generated by Cr⁴⁺:YAG crystal fibers are presented. Milliwatt ASE was obtained from a double-clad 25-mum-core fiber. Results of the experimental ASE power measurements and the composition analysis using electron probe micro-analyzer were used to determine the absorption, emission, and excited-state absorption cross sections of pump and signal of the crystal fibers. The numerical analysis showed that the ASE output power is improved by reducing the fiber core diameter down to several micrometers despite of the increased consumption in excited-state absorption of pump. A comparison of the cross sections between those in literature and this work indicates that the crystal fiber has good crystal and optical qualities using the laser heated pedestal growth method. The large pump absorption of the Cr⁴⁺:YAG crystal fiber limits its useful length. With such short fiber length, the ASE lights can not acquire enough gain. The ASE efficiency can be further improved by using bi-direction and cladding pump structure to increase the crystal fiber length and incorporating a high ASE reflector at the input end of the crystal fiber. The Cr⁴⁺:YAG crystal fiber has a potential for applying to ultra-broadband ASE light source in wavelength division multiplexing network.     

A cladding-pumped fiber laser with pump-reflecting inner-cladding Bragg grating

A fiber Bragg grating (FBG) was inscribed in the inner cladding of a double-clad fiber, in order to reflect, and thus, double-pass, the pump radiation in a cladding-pumped fiber laser. The effective pump reflectivity of the inner-cladding FBG was /spl sim/46.4%. This increased the slope efficiency of a Yb-doped cladding-pumped fiber laser by up to 8.5%, and the output power increased by 45% with a 3-W pump source. The FBG provides stable and robust pump reflection, while leaving the fiber end free, for example, so that a signal transmission fiber can be spliced to the double-clad fiber.