L波段掺铒光纤超荧光光源和放大器研究

通过优化铒光纤长度,获得了平坦谱宽达30nm(0.7dB)的L波段超荧光光源,该光源具有7.21dBm的输出功率。在此基础上,研究L波段放大器增益特性,通过对铒光纤长度的进一步优化,用1480nm激光器作前向泵浦源,实验上获得了波长从1565nm~1595nm范围平坦的增益带宽,小信号增益可达22dB。     

铒离子浓度对掺铒光纤光源性能影响研究

研究了铒离子掺杂浓度对掺铒光纤光源的泵浦效率和波长稳定性的影响.在设计好的单程后向光源中采用5种不同类型的光纤分别进行了实验,通过比较采用不同光纤时掺铒光纤光源的输出特性发现掺铒光纤光源的泵浦效率随铒离子浓度增大而先增大;铒离子浓度过高时存在群聚效应,光源泵浦效率反而下降,群聚效应使泵浦效率下降了20%.泵浦阈值则随着铒离子浓度的增加从18.3 mW增加到了32.4 mW.通过试验发现光纤优化长度依比例决定于掺铒光纤中的铒离子浓度,而泵浦波长与光源波长的关系却不受铒离子浓度影响.比较采用不同铒离子浓度光纤的光源的小范围温度特性,较低浓度的光纤温度稳定性好于高浓度的温度稳定性将近100 ppm.通过实验确定掺铒光纤中最适宜的铒离子浓度在110 mol左右.     

宽带碲基掺铒光纤放大器增益谱特性研究

建立了一个多信号共存情形下宽带碲基掺铒光纤放大器(EDTFA)四能级模型,系统研究了EDTFA 增益谱随着光纤激活长度、输入信号功率、泵浦功率和纤芯掺杂浓度的演变关系。研究表明,在输入信号功率减小、泵浦功率提高时,C 波段信号增益迅速增大;在光纤长度增长、掺杂浓度提高时,增益谱向 L 波段偏移;在小信号状态下,其 20dB 增益带宽大于 80nm。研究揭示了EDTFA 适合于作为 WDM 系统中的 L 波段和 C L 波段光纤放大器。     

光纤陀螺掺铒光纤光源消偏技术

针对泵浦偏振态对高精度光纤陀螺掺铒光纤光源平均波长稳定性产生影响的问题,设计了掺铒光纤光源泵浦消偏的结构,该结构采用Lyot光纤消偏器来对泵浦光进行消偏,理论分析了该结构中Lyot消偏器结构参数的选取.实验验证了掺铒光纤光源的波分复用器具有偏振特性,会影响掺铒光纤光源平均波长稳定性,采用设计的泵浦消偏结构可有效消除波分...     

掺铒碲基单模光纤的制备及其放大自发辐射光谱

制备了一种新型的可应用于1．5μm通讯窗口宽带放大自发辐射光源的掺铒碲酸盐玻璃单模光纤（EDTF），并分析了其热学性质和光谱特性、该玻璃显示了良好的热稳定性（△T〉150℃）和匹配的热膨胀系数．采用自制EDTF短光纤，组装了超荧光单程反向结构光源（SPB），利用波长为980nm的半导体激光器抽运掺Er^3＋的碲酸盐短光纤，可在1450-1650nm范围获得宽带宽的铒离子放大自发辐射光谱（ASE）．研究了光纤长度，泵浦功率等对放大自发辐射光谱的影响．研究结果显示，该碲酸盐玻璃是一种适用于宽带放大自发辐射光源的基质材料．     

利用打靶法模拟稳态受激布里渊散射

提出了用打靶法结合有限差分法求解稳态受激布里渊散射(SBS)耦合方程的算法.利用了先猜测,再修正的逐渐逼近的方法将边值问题转化为初值问题,从而解决了如何确定边界上的泵浦光和Stokes光的初始值的问题.在计算过程中,不仅考虑了光的损耗,而且简化了龙格库塔积分法的繁琐程序,使得计算程序简练快速,结果准确.利用该算法,模拟了不同入射泵浦功率和不同光纤长度时,泵浦光和Stokes光沿光纤的功率分布.     

1.48μm大功率GaInAsP／InP激光器

用两步液相外延法研制出１．４８μｍ大功率ＧａＩｎＡｓＰ／ＩｎＰ激光器，尾纤输出功率大于３０ｍＷ。用作掺铒光纤放大器的泵浦光源，双向泵浦小信号增益２８ｄＢ，经较长时间的实际运行，表明器件性能稳定可靠，温度特性好。     

Er3+/Tm3+共掺光纤放大器的模型和增益特性

基于Er/Tm共掺石英光纤的能级跃迁及能量转移特性,建立了Er3 /Tm3 共掺石英光纤放大器的理论模型。采用离散算法,计算了自发辐射输出功率谱和放大器的信号增益。结果表明,依据模型计算的正向自发辐射输出功率谱与实验结果基本一致;输出信号的3dB增益带宽随不同的光纤长度和泵浦功率而变化;当输入的泵浦功率为0.2W,信号功率为1μW时,Er3 /Tm3 共掺石英光纤放大器的3dB带宽可达到110nm。     

短腔的高浓度掺铒光纤激光器

本文提出采用高浓度掺铒光纤的短腔环形光纤激光器,研制出铋铝共掺和铋镓铝共掺两种石英基高浓度掺铒光纤,这两种掺铒光纤的吸收系数在1530 nm处分别达到了66.3dB/m和59.5dB/m.利用这两种石英基高浓度掺铒光纤,采用环形结构制作出了短腔的光纤激光器,光纤激光器中铒光纤长度分别仅为30 cm和90 cm.对采用这两种高浓度掺铒光纤制作的光纤激光器的输出特性进行了测试和分析.实验结果表明,采用铋镓铝共掺的掺铒光纤制作的光纤激光器具有更高的输出功率和斜率效率,在980 nm泵浦源输出功率330 mW时可以实现15 dBm的激光输出,激光器的斜率效率达到了22%.     

抑制噪声的宽带碲基掺铒光纤放大器性能分析

设计了一个带光隔离器的复合型宽带碲基掺铒光纤放大器（EDTFA）,通过对该结构模型下的速率方程和光功率传输方程组的数值模拟,理论研究了EDTFA在插入光隔离器后的性能变化。研究表明,通过插入光隔离器抑制反向传输的放大自发辐射（ASE）噪声,可以有效地改善宽带EDTFA的信号增益和噪声特性。在光纤激活长度240cm、铒掺杂浓度2000ppm和前向泵浦功率200mW下,光隔离器插入在最佳位置处时,1540nm～1600nm波段内16路信道小信号增益分别提高了0.8dB～5．9dB,噪声系数降低了0.2dB～2．2dB。研究结果对于新型宽带EDTFA应用于WDM通信系统中具有理论指导意义。     

Pump efficiency improvement of a C-band tunable fiber laser using optical circulator and tunable fiber gratings

We propose and demonstrate a tunable fiber laser based on an optical circulator (OC) and two tunable fiber Bragg gratings (TFBGs). The OC acts as a pump power router to improve the pumping efficiency, and a 4% increase in overall conversion efficiency has been observed. The combined tuning spectra range of two TFBGs could cover the entire C-band spectrum from 1530 to 1560 nm. Stable laser output power above 10 dBm is obtained using 1.9 m of erbium-doped fiber and TFBGs with 50% reflectivity. With power equalization by using variable optical attenuators, the power variation is less than 0.1 dB in the whole C band with narrow linewidth of 0.05 nm. A signal-to-noise ratio of 60 dB and a continuous tuning resolution of 0.5 nm have been achieved. The TFBG-based tunable fiber laser can be a promising light source for WDM transmission and fiber sensor applications.     

Fiber circular polarizer

A fiber circular polarizer, composed of a metal-coated fiber polarizer and a lambda/4 platelet fabricated on a birefringent fiber, has been demonstrated. The lambda/4 platelet was made by cutting a birefringent fiber to an appropriate length. The device structure was designed by stress analysis simulation using a finite element method to set the angle theta = pi/4 between the fiber polarizer axis and the birefringent fiber major axis. The 17.6-dB maximum extinction ratio was obtained when the left- and right-circularly polarized light was launched into the device. It is assumed that such a fiber circular polarizer will operate as a quasi-isolator, because the light reflected from the output, the main factor backing the light source, is eliminated.     

高功率双包层Er3+/Yb3+共掺光纤放大器的动态响应

基于速率方程的离散算法,分析了双包层Er3 /Yb3 共掺光纤放大器的动态响应,显示了输出功率和增益的动态特征。当单个脉冲注入放大器时,输出脉冲的峰值功率不仅依赖于输入脉冲的峰值功率,而且依赖于泵浦功率;当脉冲序列注入时,输出脉冲的功率和增益最终将收敛于它们的稳态值。在双信道情况下,输入脉冲重叠时的输出功率和增益变得更陡峭。在连续波泵浦下,反向自发辐射输出功率(ASE-)首先快速地增加到峰值功率,然后单调下降到稳态值;在脉冲波泵浦下,反向自发辐射输出功率(ASE )与光纤长度成反比,而ASE-与光纤长度成正比。     

Fiber-optic temperature sensors based on differential spectral transmittance/reflectivity and multiplexed sensing systems

A concept for optical temperature sensing based on the differential spectral reflectivity/transmittance from a multilayer dielectric edge filter is described and demonstrated. Two wavelengths, λ(1) and λ(2), from the spectrum of a broadband light source are selected so that they are located on the sloped and flat regions of the reflection or transmission spectrum of the filter, respectively. As temperature variations shift the reflection or transmission spectrum of the filter, they change the output power of the light at λ(1), but the output power of the light at λ(2) is insensitive to the shift and therefore to the temperature variation. The temperature information can be extracted from the ratio of the light powers at λ(1) to the light at λ(2). This ratio is immune to changes in the output power of the light source, fiber losses induced by microbending, and hence modal-power distribution fluctuations. The best resolution of 0.2 °C has been obtained over a range of 30-120 °C. Based on such a basic temperature-sensing concept, a wavelength-division-multiplexed, temperature-sensing system is constructed by cascading three sensing-edge filters that have different cutoff wavelengths along a multimode fiber. The signals from the three sensors are resolved by detecting the correspondent outputs at different wavelengths.     

碳纤维复合材料保险杠铺层优化设计研究

对碳纤维复合材料保险杠碰撞性能进行研究,并进行铺层优化设计。先在HyperStudy中进行试验设计获得大量试验数据,然后采用HyperKriging方法构建近似模型,随后采用遗传算法进行铺层优化,最后将最优解重新代入原模型,进行运算验证。相对于原钢制保险杠,优化后的碳纤维复合材料保险杠有更佳的安全性能,且质量显著减轻,减轻63.3%。碳纤维复合材料对于汽车碰撞安全性及轻量化具有重要的研究意义。     

不同掺杂浓度光纤拉曼增益特性的研究

研究了受激拉曼散射增益系数和增益谱与泵浦功率、光纤掺杂浓度的关系,得出增益系数和峰值频移量由光纤特性决定,而与泵浦功率无关的结论。在对二氧化硅分子建模计算后,进一步利用LM算法对光纤的拉曼增益谱进行高斯分解。分解图谱表明掺杂物破坏了二氧化硅的分子结构,并在拉曼增益范围内产生了新的峰值,从理论上证明了光纤掺杂物对拉曼增益系数和增益谱的影响。     

激光偏振特性对分光镜分光比影响的实验研究

在强度调制型光纤传感器的应用中,光源的功率波动是影响传感器精度的关键。采用分光镜设置参考光路的强度补偿技术虽然理论上可以实现高精度的补偿,但是由于分光镜分光比会因激光光源的偏振特性变化而改变。在分析光源偏振方向的变化对分光镜分光比影响的基础上,用仿真和系统实验进行了验证。理论及实验结果的吻合证明了分光比受光源偏振特性影响成周期性变化的结论。     

Split-spectrum intensity-based optical fiber sensors for measurement of microdisplacement, strain, and pressure

A self-referencing technique compensating for fiber losses and source fluctuations in reflective air-gap intensity-based optical fiber sensors is described. A dielectric multilayer short-wave-pass filter is fabricated onto or attached to the output end face of the lead-in-lead-out multimode fiber. The incoming broadband light from a white light or a light-emitting diode is partially reflected at the filter. The transmitted light through the filter projects onto a mirror. The light returning from the reflecting mirror is recoupled into the lead-in-lead-out fiber. These two reflections from the filter and the reflecting mirror are spectrally separated at the detector end. The power ratio of these two reflections is insensitive to source fluctuations and fiber-bending loss. However, because the second optical signal depends on the air-gap separation between the end face of the lead-in-lead-out fiber and the reflecting mirror, the ratio provides the information on the air-gap length. A resolution of 0.13 μm has been obtained over a microdisplacement measurement range of 0-254 μm. The sensor is shown to be insensitive to both fiber-bending losses and variations in source power. Based on this approach, a fiber-strain sensor was fabricated with a multilayer interference filter directly fabricated on the end face of the fiber. A resolution of 13.4 microstrain was obtained over a measurement range of 0-20,000 microstrain with a gauge length of 10 mm. The split-spectrum method is also incorporated into a diaphragm displacement-based pressure sensor with a demonstrated resolution of 450 Pa over a measurement range of 0-0.8 MPa.     

Investigation of the effects of SOA locations in the linear cavity of an O-band Brillouin SOA fiber laser

An investigation into the effect of semiconductor optical amplifier (SOA) location in an O-band Brillouin SOA fiber laser (BSFL) was performed. Better output peak power flatness was generated by placing the SOA after the nonlinear medium, which is a 20?km true wave fiber (TWF) than placing it before the TWF. A maximum power of six flat output peaks with average power of ?22.0?dBm for a BP (Brillouin pump) wavelength of 1320?nm was obtained, generated from a BSFL with a SOA located after the TWF, compared with three flat Stokes signals with the SOA before the TWF at a BP wavelength of 1310?nm. The flat peak power output for the O-band Brillouin fiber laser is important, especially in producing a good O-band source.     

SOA-based multi-wavelength source

A simple fiber laser configuration based on a semiconductor optical amplifier (SOA) is proposed for obtaining multi-wavelength oscillation at room temperature, in which a Sagnac loop mirror is used as the wavelength selective component. The SOA has a flat gain of approximately 23dB within a bandwidth of 12 nm at a small input signal power. The loop mirror was constructed using a 3dB coupler and polarization maintaining fiber (PMF). The output spectrum of the proposed laser can be adjusted by controlling the bias current of the SOA and is quite stable at room temperature. At a bias current of 150 mA, six lines are obtained with at least ?40 dBm output power and 25dB signal-to-noise ratio (SNR). The channel spacing and number of lines is determined by the length of polarization maintaining fiber (PMF) used in the loop mirror. The channel spacing of the proposed laser is 1.49 nm with a PMF 3 m. The multi-wavelength comb output can also be tuned by adjusting the operating temperature of the SOA. The multi-wavelength laser has the advantage of a simple configuration, stability at room temperature, a broad wavelength band, and no need for optical pump lasers.