基于细芯光纤内嵌马赫曾德尔干涉仪的应变传感器

研究了基于细芯光纤内嵌马赫曾德尔干涉仪的光纤应变传感器,通过将一根细芯光纤熔接在两根单模光纤(SMF)之间,构成了一种光纤内干涉的马赫曾德尔干涉仪。当单模光纤中的光耦合进细芯光纤时,一部分光耦合进细芯光纤纤芯作为芯模传输,另一部分光耦合进细芯光纤包层中激发出包层模沿包层传输,当芯模和包层模再耦合进单模光纤时发生干涉。当应变作用在细芯光纤上时,干涉条纹发生漂移。通过解调干涉条纹对应变的漂移量实现应变测量,在0~2000 με的测量范围下,测得的应变灵敏度为-1.83 pm/με,并且实验结果与理论分析有很好的一致性。该传感器具有体积小、制作简单、灵敏度高等优点。     

Optical Coupling Methods for Cost-Effective Polymer Optical Fiber Communication

In this paper, we report cost-effective light coupling methods for polymer optical fiber (POF) communication. Here, we compare the various optical coupling schemes in detail. By optical simulations, we analyze the conventional light coupling schemes, namely the direct coupling, lens coupling, and lensed fiber coupling. The simulation studies reveal that a lensed fiber tip particularly at the receiver side improves the light coupling efficiency to a great extent. The optimized lensed POF design confers an 85% coupling efficiency. Lensed POFs are realized with two low-cost fabrication methods. The characterization of the lensed POF are carried out to evaluate the lensing properties and hence to optimize the fabrication process.     

单芯光纤与毛细管光纤的耦合方法及其机理

提出了一种单模光纤(SMF)与毛细管光纤耦合的有效方法,研究了两种不同结构毛细管光纤与单模光纤的耦合问题。通过对单模光纤与毛细管光纤熔点处进行熔融拉锥实现了单模光纤与毛细管光纤之间的高效耦合。对该耦合方法的耦合机理及耦合光传输特性进行了研究、对比,并通过实验对理论预测进行了验证。该耦合技术具有简便易行、耦合效率高的特点。     

皮秒脉冲在级联光纤光栅中的传输特性研究

基于波分复用(WDM)系统中级联光纤光栅色散特性,研究了皮秒脉冲宽度以及光纤光栅长度和耦合系数等参数对脉冲压缩的影响;以高斯脉冲为例,运用等效色散的方法数值模拟了皮秒脉冲经过常规光纤和级联光纤光栅的演化过程.结果表明,选择合适的参数,级联光纤光栅可以对在普通光纤中色散展宽的脉冲进行色散补偿.还发现,进一步增加光栅长度,可使脉冲得到有效压缩.     

Wide Dynamic Range Optical Power Control Based on Cascaded Fused Tapered Couplers for High-Power Yb-Doped Fiber Lasers

Wide dynamic-range optical power control was achieved in a novel all-fiber device for a high-power Yb-doped fiber laser input using a serially cascaded fused tapered coupler pair. Torsional stress was independently applied over the coupling zones, which resulted in phase changes by photoelastic effects and subsequent linear shifts in transmission spectra. Dynamic range of 46 dB and low insertion loss below 1 dB were achieved for 1060-nm fiber laser with the incident fiber coupled power of 3.4 W. The detailed fabrication process of the device, characterization, and theoretical background are discussed.      

Arrayed Multimode Fiber to VCSEL Coupling for Short Reach Communications Using Hybrid Polymer-Fiber Lens

We report the novel method that can give high coupling efficiency between a vertical-cavity surface-emitting laser (VCSEL) array and a multimode optical fiber ribbon by using a hybrid-polymer-fiber lens technique. The coupling efficiency as high as 91% was achieved by optimizing the polymer lens curvature for the single source to the single fiber case. The longitudinal and the transverse coupling tolerances were enhanced with the introduction of a coreless silica fiber (CSF) segment between the fiber and the lens tip. The tradeoff between the high coupling efficiency and the large tolerance was experimentally observed. The technique was further applied to the coupling between a four-channel VCSEL array and a four-core fiber ribbon for short reach applications. The procedure of fabrication and the analysis of their optical characteristics are reported.     

传输矩阵法求解长短周期级联光纤光栅传输谱

基于光纤光栅的模式耦合理论,用传输矩阵法对长短周期级联光纤光栅的传输谱特性进行分析。先由耦合模方程分别得到长周期光纤光栅(LPFG)、连接光纤段和短周期光纤光栅(FBG)的传输矩阵,然后将它们相乘得到总的传输矩阵,最后再结合边界条件求得长短周期级联光纤光栅(CLBG)的传输谱。进一步对CLBG的传输谱进行了数值模拟,并通过实验进行了验证。实验结果表明,CLBG的传输谱中出现了由纤芯模和包层模耦合形成的两个谐振峰,与模拟计算的结果一致,证明了传输矩阵法求解CLBG传输谱的可行性,为CLBG在多参量传感和测量领域的广泛应用提供了理论支持。     

A poled electrooptic fiber

A simple fabrication technique, readily extensible to volume manufacturing, is presented to produce an electrooptically active fiber segment that can be simply integrated into optoelectronic devices. The fabrication technique offers a dielectric isolation structure surrounding the fiber to allow high field poling, a pair of electrodes used both for poling and for inducing an electrooptic effect that can be lithographically defined for either velocity-matched, high speed RF modulation or quasiphasematched three-wave mixing interactions, and ends of the fiber unaffected by the fabrication and available for splicing with additional fiber sections. An electrooptic coefficient, including overlap between the nonlinearity and the fiber mode, as high as 0.3 pm/V was obtained by combined temperature/electric field poling.     

基于干涉环结构的调Q光纤激光器

从光纤干涉环中受激瑞利散射(SRS)和光纤中受激布里渊散射(SBS)共同作用调Q的原理出发,研究了光纤干涉环耦合比及环长对调Q光纤激光器输出激光特性的影响。分别采用耦合比为50∶50,80∶20,90∶10的光纤干涉环在不同环长下搭建掺Er3 调Q光纤激光器进行实验。实验结果表明,干涉环的耦合比和环长是影响输出激光特性的关键因素,耦合率(~10%)的干涉环适宜产生脉冲激光,具有高耦合比干涉环的光纤激光器只有连续激光输出;环长根据干涉环耦合率(~10%)在2 m附近调整可以获得理想脉冲激光输出,环长过短时产生输出激光的弛豫振荡,反之产生输出激光脉冲的分裂。采用耦合比为90∶10,环长为2 m的光纤干涉环时,在37 mW的抽运功率下获得脉宽7.2 ns,重复频率212.4 kHz,输出功率5.4 mW的脉冲激光,脉冲波形较好,峰值功率有~30%的波动。     

一种级联喇曼光纤激光器数值模拟的新算法

为了优化设计光纤喇曼激光器的各项参量,采用喇曼激光器的基本理论模型模拟,提出了非线性最小二乘法和龙格-库塔法相结合的新算法,解决了模型中存在的两点边值问题,得到了级联喇曼光纤激光器的输出特性以及最佳光纤长度、激光阈值和斜率效率。结果表明,新算法非常有效,数值模拟的结果和相关实验相吻合。     

Highly Efficient S-Band Thulium-Doped Fiber Amplifier Employing High-Thulium-Concentration Doping Technique

In the paper, we describe in detail a highly efficient S-band thulium-doped fiber amplifier (TDFA) employing a high-thulium-concentration doping technique. A TDFA with a dual-pass configuration is superior to a TDFA with a single-pass configuration with regard to power-conversion efficiency, whereas it is inferior with regard to noise figure (NF). We propose a cascaded configuration consisting of a single- and double-pass configuration, which provides high efficiency and a low NF. The configuration generated no interference noise, which can result from multipass interference (MPI) with a double-pass configuration. We achieved gains exceeding 26 dB and NFs of less than 7 dB in the 1480-1510-nm wavelength region (30-nm bandwidth). Furthermore, an 8 times 10-Gb/s transmission experiment also confirmed that there was no MPI-induced excess noise.     

Design and performance of expanded mode fiber using microoptics

In order to relax alignment tolerances on single-mode fiber interconnection, we propose an end face treatment to realize an expanded mode fiber. This new technique consists of splicing fibers with various lengths and characteristics. The spot size and coupling properties are analyzed numerically considering the effects of gap, offset, and tilt. Low loss, wide misalignment tolerances, and low cost are achieved. The fabrication process and experiment results are presented. The performance of a connector with this expanded fiber is reported.     

Optical Packet Replicator Using Cascaded SOA-Based Active Fiber Ring

The optical packet replicator using a cascaded semiconductor optical amplifier (SOA)-based active fiber ring is proposed. By introducing the noncircular assistant light into each stage and adopting a two-stage cascaded structure, 100 replications with identity amplitude are realized. Due to accumulation of amplified spontaneous emission noise, the output signal-to-noise ratio (SNR) of the 100th replication degrades 3.8 dB, which is equivalent to the SNR degradation of 19th replication in a single ring. The number of replications can be controlled by configuring driving pulses of SOA and each interval of hundreds of replications is equal accurately. It can be employed in ultraspeed sampling without any phase jitter.     

菲涅尔反射对光纤连接器插入损耗的影响

光纤连接器在研磨完成后,纤芯端面的3D图通常显示为凹陷,即在跳线两两对接时,两光纤端面间会存在空气间隙。当光经过此光纤连接器时,在两个端面之间必定产生菲涅尔反射。基于菲涅尔反射理论,分别讨论了在计入干涉和不计干涉两种情况下光纤连接器的插入损耗,并绘制了不同空气间隙厚度时的插入损耗曲线,解释了Telcordia GR-326-CORE Issue3把光纤凹陷限定在50nm之内的实际意义。     

全分布式光纤应力传感器的研究新进展

全面综述了全分布式光纤应力传感器的发展概况.对光后向散射技术、光学非线性效应、模式耦合技术和光干涉技术的主要研究方案进行了评述,重点介绍和分析了实现高空间分辨率和动态应力测量的新技术.最后展望并讨论了全分布式应力传感器的发展趋势和应用前景.     

级联光纤环的空间全偏振态统计退偏特性研究

级联光纤环退偏器具有无源、经济、高效的特点,解决了当前发展较为成熟的Lyot型退偏器对窄带光退偏失败的缺点,是具有很大发展前景的新型退偏技术。研究了通过级联光纤环的不同循环传输路径实现光的空间分解,进而实现全偏振态退偏的统计特性。分解的各光分量由于通过不同的传输路径,其输出偏振态随机分布在所有偏振状态上。通过良好地设计光纤环长,可实现各分解光分量之间互不相干,从而实现合成输出光的统计退偏。实验实现了由10级光纤环级联实现的无需偏振控制的退偏器,对带宽为1.6nm的光源可以实现偏振度小于5%的稳定退偏光的输出。     

大模场双包层光纤熔接的功率对准技术研究

为了提高高功率光纤激光器中大模场双包层光纤的熔接质量,采用NUFERN 20/400μm双包层光纤搭建了光功率对准系统,对大模场双包层光纤中存在包层光以及纤芯中只有基模和存在高阶模时光纤径向偏移与耦合效率的关系进行了理论分析和实验验证。结果表明,大模场双包层光纤中包层光和纤芯中高阶模的存在使耦合效率对径向偏移变化的敏感度降低,滤除包层光和高阶模后耦合效率随光纤径向偏移量呈高斯型变化; 使用光功率对准系统搭建千瓦级双端抽运激光系统,最大输出功率约1170W,光光转换效率约73%,光束质量约1.22,实现了千瓦级准单模输出。光功率对准技术能够实现待熔光纤的精确对准,对高功率光纤激光器输出性能的提升有重要意义。     

用于测量折射率的光纤迈克尔逊干涉型传感器

提出了一种基于单模光纤-四芯光纤-薄芯光纤(SMF-FCF-TCF)迈克尔逊干涉结构的折射率传感器。采用直接熔接的方式将各光纤进行熔接,由于各光纤之间纤芯的直径不匹配,因此在光纤的熔接处会发生光的激发和耦合。薄芯光纤端面涂覆有一层银面反射膜并用紫外固化胶进行保护来增强光在端面的反射率。四芯光纤作为传感结构中的耦合器,激发了更多的光进入薄芯光纤的包层中,提升了传感器的灵敏度。对传感器的折射率和温度传感特性分别进行了实验探究,实验结果表明,在折射率1.3333~1.3794范围内的灵敏度为137.317 nm/RIU,线性度为0.999,并且温度对传感器的影响较小。该传感结构熔接方式简单,在折射率测量领域具有一定的应用前景。     

多阶级联拉曼光纤激光器的理论分析与优化设计

由稳态条件下描述光纤中受激拉曼散射(SRS)效应的光功率耦合方程出发,采用解析方法对多阶级联拉曼光纤激光器(CRFLs)进行了理论分析。根据拉曼光纤激光器级联阶数的奇偶性分别推导出了多阶级联拉曼光纤激光器的输出功率、光-光转换效率最大时的拉曼光纤长度和输出耦合器反射率。通过忽略反射回谐振腔输入端的剩余抽运光功率,计算了5阶级联拉曼光纤激光器的输出特性和光-光转换效率随光纤长度和输出耦合器反射率的变化。利用已有的5阶级联掺锗拉曼光纤激光器输出特性实验数据与理论分析结果进行了对比。     

保偏光纤偏振耦合系统的动态色散补偿

在白光保偏光纤(PMF)偏振耦合系统中,光纤双折射色散会引起干涉条纹包络随着光纤长度展宽,从而导致空间分辨率降低,光纤测量范围变小。为了减小双折射色散的影响,提出一种基于频域变换的色散相位补偿方法,通过干涉主极大包络与耦合点包络的宽度比求得相位补偿因子,并与非线性色散相位谱相乘,通过傅里叶逆变换得到色散补偿信号。实验分别对400m和1000m PMF进行了测试,得到光纤双折射色散系数为0.0116×10-9 ps/(nm.km),将测试系统对PMF 1000m处耦合点的空间分辨率由62.85cm提高到6.03cm,实现了对长距离PMF偏振耦合系统的动态色散补偿。