Multiwavelength-switchable SOA-fiber ring laser based on polarization-maintaining fiber loop mirror and polarization beam splitter

In this letter, we propose a novel multiwavelength-switchable fiber ring laser based on a semiconductor optical amplifier and reflection-type interleaver composed of a polarization-maintaining fiber (PMF) loop mirror and a polarization beam splitter. In the proposed fiber laser, stable interleaved waveband switching operation at up to 17 oscillating wavelengths with 0.8 nm spacing, whose switching displacement is 0.4 nm, is successfully demonstrated at room temperature by the proper control of the polarization controller within the PMF loop mirror.     

一种新颖的自反馈光注入单频窄线宽光纤激光器

报道一种基于自反馈光注入的单频窄线宽光纤激光器。激光器采用线形腔结构,用高掺杂Er3+光纤作为增益介质,利用输出信号光分束反馈与腔内振荡激光干涉,形成折射率光栅与增益光栅共同作用选择纵模,获得稳定的1 549.85 nm单频窄线宽激光输出。在975 nm单模激光二极管(LD)抽运下,激光器的抽运阈值光功率为13 mW。当抽运光功率为112 mW时,最大输出信号光功率为30.6 mW,对应的光-光转换效率为27.3%,斜率效率为30.2%,信噪比大于50 dB。采用延时自外差方法测量线宽,当使用30 km单模光纤延迟线时,测量得到激光器的3 dB线宽为4.0 kHz。     

基于双光束光源的保偏光纤定轴方法研究

现有保偏光纤侧视成像法多依赖于某特定形貌光强分布,对成像面位置调整要求高、通用性差。为了提高保偏光纤定轴灵敏度、增加方法的通用性、提高定轴稳定性,采用双光束光源取代单光束光源对保偏光纤进行侧视成像的方法,改变了以往通过调整成像面寻找特定形貌光强分布的思路,并进行了理论分析、仿真模拟和实验验证。结果表明,采用双光束光源进行侧视成像时,光强分布成双峰型,选择双峰光强值之和为特征值,建立特征值与偏转角度的对应关系,利用互相关分析可对偏转角进行确定,该方法不仅保持了透镜效应侧视法适用成像面范围广的优点,而且定轴灵敏度平均优于单光束光源侧视成像定轴法11.88%。该研究具有良好的实用前景。     

A widely tunable narrow linewidth semiconductor fiber ring laser

We have demonstrated a novel approach to obtain a 0.1-nm line width laser with 38-dB sidemode suppression by utilizing a 1.3-μm semiconductor optical amplifier in a fiber unidirectional ring that consists of a linear polarizer and polarization controllers. The laser has a low-threshold current of 22.5 mA as well as a wide tuning range of 28 nm. The new approach is applicable to the 1.55-μm region as well. It is expected that nanosecond wavelength tuning speed is feasible using this approach in conjunction with fast electrooptic polarization controllers, short cavities and low-cavity losses     

Tunable and narrow linewidth multi-wavelength Brill- ouin-erbium fiber laser using dual-wavelength pumping

We demonstrate a multi-wavelength Brillouin-erbium fiber laser (BEFL) with narrow linewidth and tunable wavelength interval using dual-wavelength Brillouin pumping. The generation of multi-wavelength output in BEFL is based on the combination of stimulated Brillouin scattering (SBS) and four-wave mixing (FWM) effect in a fiber cavity. The tunable wavelength interval is determined by the artificially controlled wavelength interval of the pumping lasers. The BEFL could compress a 1 MHz pump laser to a 340 Hz Brillouin Stokes laser, which proves the BEFL has excellent capability of linewidth compression. An erbium-doped fiber pumped by 980 nm laser is inserted into the cavity to further amplify the Brillouin laser. The wideband multi-wavelength BEFL covering over 50 nm is successfully generated when the 980 nm pump power is 400 mW. These features of multi-wavelength BEFL provide an effective method for optical communication systems and optical fiber sensing.     

A novel polarization splitter based on octagonal dual-core photonic crystal fiber

A novel polarization splitter based on octagonal dual-core photonic crystal fiber(O-D-PCF) is proposed. The impacts of several fiber parameters on the coupling characteristics of the polarization splitter are investigated by full-vectorial finite element method(FV-FEM) in detail. Through optimizing the fiber configuration, a 4.267-mm-long polarization splitter with a bandwidth of 37 nm is achieved, and its extinction ratio(ER) is as high as 81.2 d B at the wavelength of 1.55 μm. Compared with the hexagonal dual-core photonic crystal fiber(H-D-PCF) based polarization splitter, both ER and bandwidth of the O-D-PCF based one are effectively improved.     

A low-loss beam splitter with an optimized waveguide structure

Novel beam splitters with optimized waveguide structures are designed and fabricated using reactive ion etching. At 1.15 μm the excess loss of the beam splitter is measured to be 1.2 dB for TE and 1.8 dB for TM polarizations, respectively     

基于相位调制器的宽带窄线宽的线性调频激光源的产生

提出了一种基于相位调制器(PM)和可调谐光滤波器产生线性调频激光信号的方法。该方法利用带有基频的微波线性调频信号作为相位调制器的驱动信号,窄线宽的激光种子源经相位调制器调制后产生一系列的宽带线性调频激光信号。通过可调谐光滤波器抑制其他边带保留所需阶次的线性调频激光信号。实验结果表明:当光滤波器保留正二阶调频激光信号时,获得了调频带宽为2 GHz、调频速率为6 THz/s的线性调频激光信号。在观测时间为1 ms时,测得的线性调频激光信号的瞬时线宽为3.2 kHz。该方法结构简单,易于实现,并且对调频连续波激光雷达、相干光谱分析等测量应用有重要意义。     

一种新型的圆偏振光分束器的设计及分析

对两种旋向相反却又各向同性的旋光晶体进行组合,可以获得一种新型的圆偏振光分束器。本文计算了波长为300nm-800nm的偏振光通过此类器件后产生的左右旋圆偏振光的分离角,并对其相关的性能进行了分析。计算结果表明:对于两块晶体所组成的器件,左右旋圆偏振光之间分离的最大角度超过0.2°。此类器件的特点是由各向同性的旋光晶体构成,光在其内部传输时,具有的圆偏振状态不会因传输方向而变,经过器件后的左右旋圆偏振光都是严格的圆偏振光。     

一种用于DWDM系统的薄膜型微小偏振分束器

讨论了一种用于DWDM系统中的光开关、偏振无关隔离器等单元器件中的微小薄膜型偏振分束器制造的关键技术.光学膜层采用数学多重优化设计方法;采用Monte Carlo允差分析原理分析膜层的容差,以便选择更易制备的膜系;计算膜层的Macleod极值灵敏度,得到所选膜系各个膜层的误差要求;模拟光学监控过程,以制定相应的膜厚监控策略.设计了实用的棱镜胶合装置,得到了较高技术指标的PBS棱镜.结果表明,棱镜的光学冷加工,是器件制造的基础;光学薄膜的设计与制备是器件制造的关键,也是难点;棱镜的胶合是器件不可忽视的环节.     

光源谱型对保偏光纤应力传感信号的影响

保偏光纤对入射的线偏振光具有偏振保持能力,用白光干涉系统可实现准分布式应力、温度和位置传感。超辐射发光二极管(SLD)当驱动电流较小时,光谱服从高斯分布;随着驱动电流增加,中心波长向短波方向漂移,光谱畸变,可用两个高斯函数相加拟合。本文详细分析了SLD光源在不同驱动电流下的谱型分布及拟合曲线,并在保偏光纤应力传感系统中进行了实验,实验结果表明随着光源输出功率增加,在耦合点两侧对称分布着伪耦合点。当光源功率为15 mW时,伪耦合点的耦合强度比力致耦合点的耦合强度约小15 dB。     

A novel polarization splitter based on the photonic crystal fiber with nonidentical dual cores

A novel polarization splitter based on photonic crystal fibers (PCFs) with two nonidentical cores is proposed. The two highly birefringent cores are vertically arranged to obtain polarization selective coupling. The horizontal polarization exchanges its energy between the two cores. However, the vertical polarization shows little coupling between the two cores. This is achieved in single-material glass waveguides for the first time to our knowledge. The PCF-based polarization splitter exhibits many advantages such as shorter length, high extinction ratio, and wide bandwidth over its counterparts.     

A polarization splitter on LiNbO3 using only titaniumdiffusion

A novel polarization splitter is proposed for use in integrated optical circuits on lithium niobate. In contrast to previously reported devices, its operation is based on the mode sorting effect with no external control, while its fabrication requires only a single technology: the diffusion of titanium. The splitter is formed by a Y junction. The polarization splitting can be achieved by making the output waveguides from two titanium strips with different dimensions. A realistic design of these output guides is presented, and some technological aspects are discussed. The operation of the polarization splitter is investigated with the beam propagation method. The results show that a 15-dB extinction ratio is obtained with branching angles larger than 0.2°. The extinction ratio can be as high as 30 dB with a branching angle of 0.1°. The excess losses are below 0.05 dB     

A depolarized Er-doped superfluorescent fiber source with improvedlong-term polarization stability

In a backward Er-doped superfluorescent fiber source (SFS), we report the observation of large mean wavelength variations (>100 ppm) induced by external perturbations of the fiber birefringence. These previously unreported variations, which need to be reduced to the ppm level for high-accuracy fiber-optic gyroscope applications, are shown to originate first from polarization-dependent gain induced by the polarized pump source, and second from a slight polarization dependence of the SFS wavelength division multiplexing (WDM) coupler and fiber isolator. We demonstrate that these effects can be substantially reduced by incorporating two Lyot fiber depolarizers in the source. The new depolarized SFS exhibits short-term mean wavelength stability of ±2.5 ppm and a long-term drift of ±3 ppm. The latter is probably due mostly to slow variations in the Er-doped fiber temperature, which can be eliminated with a simple temperature control to ~0.1°C     

A linewidth formula for semiconductor-optical fiber ring lasers

The authors derive a formula of linewidth for a semiconductor-optical-fiber ring laser by using coupled rate equations for the active and passive cavity. It is shown that the linewidth is not only the function of the two-cavity length ratio and time delay in fiber, but also the function of light intensity ratio of the two cavities and the phase shift introduced by junctions between the gain medium and the optical fiber     

A novel waveguided polarization mode splitter using refractiveindex changes induced by superlattice disordering

The operating principle of our polarization mode splitter is based on the polarization-dependent refractive index changes induced by disordering InGaAs/InP superlattices. We disordered superlattices by the Si₃N₄ cap-annealing method and measured the near-field patterns to confirm that the device functioned properly at a wavelength of 1.52 μm. The crosstalk was about -10 dB. We should be able to improve the characteristics of this device by optimizing its structure. This device requires no electrical control and will be very suitable for semiconductor monolithic integrated circuits     

LOCNET: a fiber in the loop system with no light source at thesubscriber end

An optical subscriber loop with simultaneous video and bidirectional data transmission over the same fiber is presented. A reflective modulator replaces the light source at the customer end. The system has been tested and experimental results are described     

一种带环形器的双抽运掺铒光纤光源

把光纤环形器使用在掺铒光纤光源的结构中,得到C L波段的宽带光源.采用这种结构,通过调节三个激光二极管的控制电流到合适的数值,可以让输出光的功率提高到168.67mW(22.27dBm),带宽达到80.701nm(1525.112～1605.813nm).同时通过实验发现,研制的光源不仅有较高的功率,而且输出光平坦.     

用于Rb蒸气激光泵浦的可调谐窄线宽半导体激光器

由于Rb蒸气的吸收峰随缓冲气体气压存在漂移,利用体布拉格光栅(VBG)实现线宽压窄的同时,实现泵浦半导体激光器中心波长的可调谐也是十分必要的。本文采用国内封装的半导体激光阵列(LDA),利用VBG的温度特性,实现了线宽不大于0.3nm的同时,激光器中心波长从779.89nm到780.35nm可调谐。该激光器可以通过叠阵方式用于Rb蒸气的泵浦和激励。     

基于多点耦合内切的光纤谐振环慢光系统转动传感理论

为满足惯性制导对高精度、高稳定度陀螺仪的需求,进行了对基于高色散谐振环结构的光纤陀螺原理研究.在一些高色散耦合谐振环结构中,其色散性质使其系统传递函数对相位微扰十分敏感,可以对萨格纳克相移起到放大作用,从而大大提高传感灵敏度.理论与仿真研究结果表明:多点耦合内切谐振环慢光结构系统能够同时满足实现高灵敏度转动传感所要求的“方向性条件”和“高群折射率(慢光)”两个基本条件,且具有进一步使群折射率比传统结构高出几个数量级的潜力.同时,由于该结构系统可使用定向耦合器来方便搭建,具有用来制作低成本、高灵敏度的光纤陀螺的潜力.