Experimental Measurement of Fused Fiber Coupler and M-Z Interferometer Performance as WDM Devices

An experimental study of the WDM response of fused fiber couplers and an M-Z interferometer is presented. The WDM practical implementation limits of single fused fiber couplers, along with fiber tapering measurements, were obtained. Mach-Zehnder interferometric devices based on fused fiber couplers were included in this work in order to surpass the single coupler's WDM limitations and widen the operation range of the analyzed fused fiber devices.     

Small-scale integration of fused tapers

The Small-Scale Integration (SSI) of fused couplers is proposed. The idea is to make several couplers on a single continuous piece of fiber rather than making discrete couplers and then splicing them together. Rudimentary tooling was set up to fabricate the couplers. Nine devices were successfully integrated onto a single fiber. In addition, a theory of fused tapers was developed. The fabrication parameters are analytically related to fiber geometry, which in turn, is related to the optical performance of the device.     

Fused biconical tapered fiber-optic devices: Application to data buses

Abstract

The technology of fiber-optic couplers based on fused biconical tapered structures is reviewed, and the linear and star data-bus configurations that can be constructed using these couplers are discussed. A useful network topology for interconnecting star couplers using the hybrid transmission-reflection star coupler is also proposed. This network configuration has the advantage of requiring significantly less optical fiber than networks employing a single transmission or reflection star.     

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].     

Binary phase gratings for couplers used in fiber-optic communications

Abstract

Star couplers and bidirectional couplers for use in fiber optic networks have been constructed using binary phase transmission gratings. The principles of operation and the performance of these devices are discussed. Experimental results are shown which agree with the theoretical predictions to an accuracy of 0.5 dB.     

Fused-Polished Fiber Couplers

We report on fused-polished fiber couplers with a new fabrication method. This structure so fabricated is promising while achieving high-performance all-fiber WDM devices. Potential advantages and prospects of our works are presented.     

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.     

2×2熔锥型单模光纤耦合器的模型

选择适当的连续函数描述了熔锥型耦合器熔锥形状的渐变特性及其相互位置关系,然后分别应用局部模式理论和变分法分析了横截面沿纵向变化的锥形区域和横截面近似不变的耦合区域内的耦合行为,得出了耦合器中任一横截面处的耦合系数和耦合功率表达式计算表明,熔锥型耦合器的总功率耦合主要发生在耦合区域,在两锥形区域,对于纤芯归一化频率小于1.08的部分,也发生了相当程度的耦合为了使耦合器的理论模型更接近于实际物理情况,锥形区域的耦合作用也是不容忽略的,从而得到了一个更精细的熔锥型光纤耦合器的模型.     

An ASE Reduction Filter Using Cascaded Optical Fiber Grating Couplers in EDFA Repeater

A new configuration for an ASE reduction filter in EDFA repeaters for WDM optical transmission systems using optical fiber grating couplers (FGCs) was proposed and first demonstrated. The filtering characteristics of the proposed filter for amplified single wavelength signal and 2-channel WDM signals using EDFA were identified. It was found that the filter was effective to improve SNR in optical domain by reducing ASE noise. The required FGC characteristics for the filter were theoretically predicted under the condition that the total filter loss did not exceed 3 dB. More than 70% of drop efficiency was required in each FGC for the application of the proposed filter to an 8-channel WDM system using EDFA repeaters.     

单模光纤1250～1650 nm超平坦宽带耦合器

随着光纤技术的飞速发展和应用．光纤无源器件顺应当前形势也获得很大的发展空间,其中光纤熔锥器件具有制作简单、性能可靠、价格便宜及技术指标优越等优点,从而广受青睐。在熔锥器件中,光纤耦合器是广为应用的基础元器件。目前为实现全光通信。光纤超平坦宽带耦合器则成为热点课题。利用特殊相位补偿工艺方法,研制出单模光纤超平坦宽带耦合器。其工作波长范围为1250～1650nm,3dB带内最大插损偏差小于等于0．4dB,带内最大附加损耗小于等于0．1dB,方向性(输入侧非注人光的一端的输出光功率与注入光功率的比值)大于等于66．5dB,偏振相关性小于等于0．1dB。研制方法有很高的成品率,可批量生产。     

Fused biconical tapered fiber-optic devices: Application to data buses

The technology of fiber-optic couplers based on fused biconical tapered structures is reviewed, and the linear and star data-bus configurations that can be constructed using these couplers are discussed. A useful network topology for interconnecting star couplers using the hybrid transmission-reflection star coupler is also proposed. This network configuration has the advantage of requiring significantly less optical fiber than networks employing a single transmission or reflection star.     

Characteristics of WDM Couplers Based on 80 μμ m Cladding Fiber

We have fabricated 1310/1550 and 1480/1550nm WDM couplers using a fiber of 80 μm cladding diameter,whose tapering length is shortened by 4～8mm for the identical coupling strength compared to those of 125μm cladding fibers. We also report their splicing loss to conventional single mode fibers.     

Crosstalk in a bidirectional optical fiber

Abstract

Full-duplex communications in a single optical fiber is both feasible and practical in certain applications. The main problem is crosstalk between the two directions. This paper reviews the sources of crosstalk, gives its magnitude, and describes techniques to reduce crosstalk. An example is a system that requires 75 optical dB of isolation between transmitted and received signals at each terminal. There are two sources of optical crosstalk. The first occurs in components such as couplers and connectors and can be held below 50 dB by careful design. The second is Rayleigh scattering within the fiber, which increases system noise as well as crosstalk between counterdirectional signals.     

高性能三端口全光纤开关

提出采用２×２和３×３单模光纤耦合器组合成的马赫－陈德尔干涉仪来制作全光纤开关。解决了在连续熔融拉伸两个耦合器组成马赫－陈德尔干涉仪的过程中，由于干涉的作用而无法监视光功率来控制第二个耦合器的分束比的问题。并且由于是连续熔融拉伸，保证了两条单模光纤干涉臂长度的一致，从而提高了单模光纤马赫－陈德尔干涉仪的性能，使得用其做成的三端口压电陶瓷电控全光纤开关具有宽频带的特性，其最小交调达到３０ｄＢ，附加损耗为０．２３ｄＢ。     

300 W侧面分布式抽运掺Yb全光纤放大器

采用角度磨抛的方式, 在纤芯/包层为20/400 μm双包层掺Yb光纤上制作了侧面抽运耦合器. 该耦合器对975 nm的半导体二极管抽运光的耦合效率最高可达97%, 对1080 nm信号光的泄漏比小于2%. 分析了侧面抽运耦合器的性能以及多个侧面抽运耦合器的级联分布对抽运耦合效率的影响; 同时, 在前向抽运和双向抽运方式下, 分析了级联耦合器的分布及信号光泄漏比对激光器整体效率的影响, 并进行了数值模拟. 采用自行研制的侧面抽运耦合器, 搭建了侧面耦合分布式抽运、掺Yb双包层全光纤主振荡功率放大器, 获得了波长为1080 nm、功率为303 W 的基模激光输出. 进一步增加抽运点个数, 提高抽运功率, 可获得更高的输出功率.     

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].     

熔锥型光纤耦合器宽带特性研究

报道了在常规熔锥型单模光纤定向耦合器工艺基础上，以氢氟酸腐蚀法，将两光纤耦合区直径腐蚀成适当比例，用水平直接熔融拉锥系统，将耦合区域拉制成非对称臂组合波导，从而获得了具有宽频带特性、且尺寸较小的单模光纤定向耦合器，实验结果说明：通过控制耦合区长度，可以使耦合器耦合功率在某个特定波长附近、预定小于１００％分束比上具有相当平坦（宽带）特性；从而，通过控制组合波导的不同直径比，可望得到不同分束比宽带耦合     

Photonic crystal fiber coupler

Fiber couplers made with photonic crystal fibers (PCF) are reported. Two types of PCF were fabricated by means of stacking a group of silica tubes around a silica rod and drawing them. The fiber couplers were made by use of the fused biconical tapered method. With a fiber that had five hexagonally stacked layers of air holes, a 33/67 coupling ratio was obtained, and with a one-layer four-hole fiber, a 48/52 coupling ratio was obtained. The fabrication processes and the characteristics of the PCFs and the PCF couplers are presented.     

熔锥型保偏光纤耦合器分光比的偏振依赖研究

实验研究了熔锥型保偏光纤耦合器分光比随入射单色线偏振光偏振方向的旋转所呈现的周期性,验证了保偏光纤耦合器分光比的偏振依赖特性.借鉴已成熟的单模光纤耦合器的倏逝场耦合模理论,对这一偏振依赖分光比的周期性规律提出了一种理论解释.在实验结果的规律性基础上,经验拟合出了分光比与单色线偏振光输入偏振角的函数关系.     

3-D Electromagnetic Modeling of Polarization-Dependent Coupling Characteristics of 1×3 Linear Array Weakly Fused Fiber Couplers

Based on the full-wave surface integral equations method and the steplike approximation technique, a three-dimensional (3-D) electromagnetic model for simulating polarization-dependent power-coupling behavior of 1×3 linear array weakly fused fiber couplers is proposed. The accuracy of the proposed numerical model is confirmed to be good by comparing with the measured power transfer behavior at the fusing and elongating process of the couplers. In the 3-D modeling view, the polarization-dependent coupling behavior of two practical couplers, 1/3 power splitter and wavelength-flattened coupler, are numerically studied. It is seen that as the coupler is designed in a very weakly fused condition the polarization-dependent loss (PDL) is significantly increased. For designing the 1×3 coupler with low PDL, it is suggested that the aspect ratio has to be controlled in stronger fused range between 0.8 and 0.9.