Passive fiber-optic components made by the fused biconical taper process

The rapid development and deployment of optical fiber for a variety of applications has resulted in a similarly rapid development of myriad components to effectively utilize the fiber. Thus, for example, significant work has been done over the past several years in the development of sources and detectors, connectors, and splices. These components share the common trait of being external to the fiber and hence not part of the fiber per se. Another class of components, however, is made from the fiber itself. A number of components, such as polarizers, analyzers, and mode or wavelength filters, require only simple bending of the fiber in a specified manner. On the other hand, such techniques as polishing, etching, and heating can also be used to alter the transmission properties of the fiber.

While a number of interesting devices have been made by these procedures, the present paper is limited to devices made by the biconical taper process. If a fiber is heated and stretched, a biconical taper is formed, which can significantly alter the transmission characteristics of the fiber. Interesting wavelength filters and sensors can be made with single tapers or combinations of tapers. Moreover, if two or more tapered fibers are fused, then coupling of light from one fiber to another can be achieved. The tapering and fusing processes can be used to make wavelength-enhanced couplers, which can be used as wavelength-division multiplexers or nearly wavelength-independent couplers or splitters.

In this paper, we discuss the components made by the biconical taper process, their fabrication, in both theory and practice, and their performance. Practical implementations of these components are also discussed, including their manufacturability and reliability.     

面向地壳形变观测的超高分辨率光纤应变传感系统

高分辨率光纤应变传感系统是地球物理学中地壳微弱形变观测的有力工具.相比于传统的地壳应变观测技术,光纤应变传感器具有测量分辨率高、抗干扰能力强、尺寸小、可复用、易于安装布设等特性,在建立新型地壳形变监测网络中具有很大的应用潜力.本文围绕面向地壳形变观测的纳应变级分辨率光纤应变传感器技术,阐述了应变传感原理与实现超高测量分辨率的机理,并详细介绍了扫频探测、Pound-Drever-Hall解调技术、边带探测、双回路锁定传感、传感器时分复用等技术及相应的传感器系统实现方案,最后,给出了超高分辨率光纤传感器在现场观测的实验结果与分析.     

一种血流变参数在体实时探测方法

介绍了一种新的在体实时监测血流变参数的光学方法——光散射法。设计了一种实用的同轴多光纤探针装置。在装置中间,其中一根光纤用于传输入射激光,周围多根光纤与中心光纤等间隔,用于接收血液中的散射光。用扫描法布里-珀罗干涉仪产生散射光谱。结果表明,用该装置测得了含成分的液体、实血和不同血液成分的光散射光谱。     

Self-healing ring-based WDM-PON

In this paper, a survivable ring-based wavelength-division-multiplexing (WDM)-passive optical network (PON) for fiber protection is proposed. Protections for feeder fiber and distributed fiber are independent in the scheme. Optical line terminal (OLT) and optical network units (ONUs) can automatically switch to protection link when fiber failure occurs. Protection distributed fiber is not required in the scheme. Cost-effective components are used in ONUs to minimize costs of network. A simulation study is performed to demonstrate the scheme. Its result shows good performance of upstream and downstream signals.     

Low-cost,high performance optoelectronic components for antenna remoting

We describe a demonstration of a system in which we incorporated components developed as part of the DARPA Analog Optoelectronic Module Technology Project (TRP). The goal of the TRP program was to bring to manufacturability fiber optic components whose specifications are adequate for both military and commercial applications but whose cost is substantially less than the presently available components. We demonstrated the functionality of the TRP components by using them in a fiber optic link designed to replace one of the coaxial cables that perform antenna remoting in a phased array. For this antenna remoting demonstration, we used an existing linear array at the Makaha Ridge, MIT Lincoln Laboratory Facility. Ordinarily, each subarray is connected to the programmable array computers in the control trailer with coaxial cable. The performance of the array with all coaxial cables connected to each subarray was compared to the case with one of the coaxial cables replaced by the fiber optic link. The results showed no degradation in the performance of the linear array with the TRP fiber optic link replacing one of the remoting coaxial cables.     

Multiple fiber Bragg grating interrogation based on a spectrum-limited Fourier domain mode-locking fiber laser

A novel fiber Bragg grating (FBG) sensing system based on a spectrum-limited Fourier domain mode-locking (SL-FDML) fiber laser is proposed. Multiple FBGs cascaded in a long fiber are utilized as both the sensors in the system and the wavelength-selected components in the SL-FDML fiber laser. Both wavelength-division multiplexing and spatial-division multiplexing techniques are demonstrated for interrogation of multiple FBGs by mapping the wavelength measurement to the time measurement and by adjusting the driving frequency of the SL-FDML fiber laser. The proposed FBG sensing system, employing techniques of the wavelength- and spatial-domain interrogation of multiple FBGs, can be used in remote and quasi-distributed multipoint sensing.     

单光纤光纤陀螺误差分析

单光纤光纤陀螺采用的是单光纤在线制作技术。由于这种方法是把所有的光器件都放在一根光纤上制作,因此各光器件的连接处没有融接点,并且光器件的性能可在线控制。在分析其结构的基础上建立了开环FOG的光学模型,并进行了误差分析。指出了单光纤光纤陀螺方案是低成本、高可靠性、易于工程化的一种方案。     

一种基于阶梯状非线性光纤的新颖脉冲压缩方法(英文)

提出了一种基于阶梯状非线性光纤的脉冲压缩方法.阶梯状非线性光纤包括普通单模光纤,色散位移光纤和高非线性光纤.数值模拟中所使用的所有元件均在现实中存在,并且与其他脉冲压缩方法相比,此方法成本低且易于控制.数值模拟表明:12.5 ps脉宽,300 mW峰值功率的双曲正割脉冲可被压缩至1.28 ps脉宽,1.3 W峰值功率的脉冲.     

球形光纤端面效应及其应用

本文介绍了球形光纤端面的制作方法,采用射线理论和等效透镜法分析了圆球形端面多模光纤的端面效应,并给出了两个不同端面多模光纤之间耦合的实验结果。结果表明：圆球形端面光纤具有聚光特性,与平端面相比,使用圆球形端面光纤不仅可以提高光器件之间的耦合效率,而且增大了它们之间的耦合距离,利于光路调试;可广泛应用于光源与光纤、光纤与光纤、光纤与探测器之间的耦合。     

A review of biconical taper couplers

Abstract

An optical coupler distributes light from a main fiber to one or more branch fibers. Optical signals can also be passed bidirectionally along a single fiber [1]. Usually couplers are passive devices which are attached to other components in a system by means of optical fiber connectors, or may be joined to them by splicing. Several basic coupler designs have been discussed in the literature, each having some advantages and disadvantages. The biconical taper coupler [2] consists of two fibers that are fused and subsequently tapered. These fibers may have step or graded index profiles. Beam-splitter types [3] (consisting of discrete components) are generally expensive. Mixing rods are simple and can be ruggedly constructed, but an extra 3dB loss above packing fraction loss is incurred when used with graded index fibers [4].     

A review of biconical taper couplers

An optical coupler distributes light from a main fiber to one or more branch fibers. Optical signals can also be passed bidirectionally along a single fiber [1]. Usually couplers are passive devices which are attached to other components in a system by means of optical fiber connectors, or may be joined to them by splicing. Several basic coupler designs have been discussed in the literature, each having some advantages and disadvantages. The biconical taper coupler [2] consists of two fibers that are fused and subsequently tapered. These fibers may have step or graded index profiles. Beam-splitter types [3] (consisting of discrete components) are generally expensive. Mixing rods are simple and can be ruggedly constructed, but an extra 3dB loss above packing fraction loss is incurred when used with graded index fibers [4].     

高功率掺镱光纤激光器的辐照影响分析及研究进展

高功率掺镱光纤激光器在空间环境中的应用日益增多,但掺镱光纤材料在空间辐照条件下会产生色心效应,导致损耗增加,影响光纤器件以及激光器整机的性能,从而给高功率光纤激光器在空间环境的长期稳定工作带来隐患。从空间辐照对高功率光纤激光器性能的影响机理、抑制方法和研究进展等3个方面进行介绍。首先介绍了空间辐照对高功率掺镱光纤激光器中关键光学器件、放大级热负载、非线性效应等方面的影响分析,其次介绍了抑制辐照效应的典型方法及其在高功率掺镱光纤激光器中的可行性分析,最后介绍了国内外典型的高功率掺镱光纤激光器的辐照影响及抑制的研究成果,并展望了未来发展趋势。     

HATR和FTIR分析彝药四块瓦和五气朝阳草

本文应用HATR和FTIR两种方法测试分析了彝药四块瓦和五气朝阳草的药物有效成分。四块瓦主根的主要成分、药物有效成分和须根的差别较大,四块瓦主根的主要成分有木质素和淀粉,须根表面层光谱主峰在1008.5cm-1处,是由纤维素νc-o振动峰产生的。主根表面层中多糖成分的934 cm-1和846.7 cm-1吸收峰,有增强机体免疫力,抗肾炎作用,为四块瓦的“补养肾脏”的疗效给出分子依据。主根和须根中都含有1731 cm-1吸收峰,1731 cm-1峰有生物碱成分的贡献,生物碱有抗菌、抗病毒作用。实验结果表明,五气朝阳草表面层的HATR图谱中含有三萜化合物和多糖成分的吸收峰,表明其表面的物质具有活血作用,其生物活性较内部强。表面层物较其内部成分更具有药用效果。此外在五气朝阳草表面层的HATR和粉末样品的FTIR光谱中都出现生物碱成分的吸收峰,说明在其表面层和内部物质成分都具有杀菌和抗病毒作用。实验表明:HATR-FTIR法对于直接测试中药材的不同部位的有效药物成分信息有优势,而FTIR压片法则能给出药材整体的平均有效药物成分的信息。     

拉曼光谱特征提取在化学纤维定性鉴别中的应用

拉曼光谱作为快速、无损的检测技术受到越来越广泛的关注,已经成功的应用于过程监控、质量监测、考古鉴定等领域。针对纺织纤维拉曼光谱的特性,提出了一种基于特征提取的拉曼光谱定性鉴别方法。该方法通过直接测取织物、纤维的激光拉曼光谱,并结合光谱预处理技术与特征峰提取、匹配识别方法,能够定性地鉴别织物、纤维的成分归属,对纺织品检验中的难点化学纤维成分的鉴别效果尤其显著。利用94份测试样品对织物成分中普遍存在的4种纤维品种——涤纶、腈纶、锦纶和粘胶进行了鉴别以验证算法的有效性。实验结果表明,该鉴别方法快速、有效,并具有很好的扩展性能,且该方法属纯粹的光学方法,需要样品量少、无需前处理,测试过程对样品无损,不产生化学污染物,适宜对各类织物成分的定性鉴别,突破了现有检测方法存在的局限。     

Single-mode fiber gyroscope with three depolarizers

In this letter we present a single-mode fiber gyroscope (FOG) with low long-term drift. Only single-mode fiber components except for three fiber depolarizers were used. A simplified mathematic model has been proposed to explain the bias stability of the gyro. Several open-loop and closed-loop FOGs with 0.1–0.5°/h drift have been demonstrated.     

The competitiveness of U.S. manufacturers in the global market for fiber optics

U.S. manufacturers of fiber optic equipment continue to be major competitors in the world markets for these products. U.S. producers account for approximately half of the total worldwide production of optical fiber and cable. In active components for fiber optic transmission systems (transmitters, receivers, amplifiers, and related components), U.S. firms are beginning to recapture some of the market share previously lost to foreign competitors. This article provides a brief overview of the competitiveness of U.S. manufacturers in the global market for fiber optic equipment, with particular focus on European and Japanese competitors.     

Optical Pulse Compression Schemes That Use Nonlinear Bragg Gratings

Nonlinear optical pulse compression of picosecond pulses typically requires long lengths of optical fiber and multiple components. Periodic structures, such as fiber Bragg gratings, are highly dispersive at wavelengths outside of the photonic bandgap. This implies that such gratings can be used as very short all-fiber compressors. In this paper a number of such compression schemes are reviewed involving uniform and nonuniform fiber Bragg gratings, relying on both soliton and nonsoliton compression principles. Experimental results supporting the corresponding underlying theory are also presented. Finally, an extension of one of the compression schemes is shown, which allows the generation of adjustable high-repetition rate soliton trains.     

Optical Pulse Compression Schemes That Use Nonlinear Bragg Gratings

Nonlinear optical pulse compression of picosecond pulses typically requires long lengths of optical fiber and multiple components. Periodic structures, such as fiber Bragg gratings, are highly dispersive at wavelengths outside of the photonic bandgap. This implies that such gratings can be used as very short all-fiber compressors. In this paper a number of such compression schemes are reviewed involving uniform and nonuniform fiber Bragg gratings, relying on both soliton and nonsoliton compression principles. Experimental results supporting the corresponding underlying theory are also presented. Finally, an extension of one of the compression schemes is shown, which allows the generation of adjustable high-repetition rate soliton trains.     

Three-cascaded 1407-nm Raman laser based on phosphorus-doped silica fiber

We report a laser-diode-pumped 1407-nm Raman fiber laser with an output power of 1 W. In this three-cascaded cw Raman laser, based on a single active phosphorus-doped silica fiber, for the first time to the authors' knowledge successive generation of Stokes components of essentially different frequency shifts (1330 and 490cm(-1)) has been realized. These Stokes components are associated with both constituents (P(2)O(5) and SiO(2)) of the fiber core glass.     

Fiber-optic interferometric point thermometer

A modulation technique suitable for short optical fiber interferometric sensors is presented. This is a passive technique that makes use of modal properties of highly birefringent fiber to generate quadrature output components. Experimental results are presented for 2 miniature, remote Fabry-Perot interferometers fabricated from 2 different types of highly birefringent fiber using this signal processing method.