Effect of Launching Condition on Modal Power Characteristics of Multi-Mode Step-Index Optical Fiber: A Theoretical and Experimental Investigation

Abstract

This article investigates optical power transmission characteristics with varying launching conditions concentrating on weakly guiding, step-index highly multi-moded optical fibers. A single analytical expression for the fractional power transmitted per mode in a highly multi-moded fiber is obtained. This expression is used to numerically obtain the fractional power per mode, power per modal order, and finally, the total power carried by the fiber. Experiments are carried out to investigate the effect of launching conditions on the total power carried by the fiber and to establish a possible correlation with the theoretical results. Reasons for the observed experimental discrepancies are also discussed.

     

Design of Fiber-Laser Arrays with Genetic Algorithms

The optimization of the far-field pattern of fiber-laser arrays is investigated based on genetic algorithms. A derived objective function of the far-field pattern performs the task of evaluating each of the fiber-laser designs generated by the genetic algorithm. The constrained parameters of the design included are radius of the fiber a, the important V value, the fiber-to-fiber separation S, and the operational wavelength . As results, sidelobe level is optimized to be -38.83 dB for a circular arrays with the given constrained parameters.     

Challenges and Solutions in Fabrication of Silica-Based Photonic Crystal Fibers: An Experimental Study

Abstract

The fabrication process of photonic crystal fibers based on a stack-and-draw method is presented in full detail in this article. In addition, improved techniques of photonic crystal fiber preform preparation and fabrication are highlighted. A new method of connecting a handle to a preform using only a fiber drawing tower is demonstrated, which eliminates the need for a high-temperature glass working lathe. Also, a new technique of modifying the photonic crystal fiber structural pattern by sealing air holes of the photonic crystal fiber cane is presented. Using the proposed methods, several types of photonic crystal fibers are fabricated, which suggests potential for rapid photonic crystal fibers fabrication in laboratories equipped with and limited to only a fiber drawing tower.     

Aging and Degradation of Optical Fiber Parameters in a 16-Year-Long Period of Usage

ABSTRACT

The first generation of installed optical cables in Eastern Europe has been in use for more than 20 years. This paper analyzes the change of optical fibers from the aspect of aging under the influence of transmitted signals and the aspect of parameter degradation during exploration. The paper provides the answer for how to repair the increased attenuation at 1310 nm. We also proposed the method of solution NG PON access for small remote villages that are situated along the analyzed route.     

The Design of Hermetically Double-Coated Optical Fibers to Minimize Hydrostatic Pressure–Induced Stresses

The design of hermetically double-coated optical fibers to minimize hydrostatic pressure–induced stresses is investigated. Several stresses are important in the hermetically double-coated optical fibers, and they would produce the excess bending losses or the failure of hermetic coatings. These stresses can be minimized by appropriately selecting material's properties of hermetic coatings and their thicknesses. The hydrostatic pressure–induced stresses in optical fibers with some selected metallic coatings are also considered. The results show that chromium has the best performance in the minimization of hydrostatic pressure–induced stresses. However, lead and indium are poor materials.     

Design of a Novel Mid-Infrared Single-Polarization Single-Mode Photonic Crystal Fiber with Low Loss,High Nonlinearity,and Large Bandwidth

ABSTRACT

A novel mid-infrared Ge₂₀Sb₁₅Se₆₅ chalcogenide-based single-polarization single-mode (SPSM) photonic crystal fiber (PCF) with rectangular latticed circular air holes is proposed. The properties of SPSM bandwidth, confinement loss, and nonlinearity are analyzed in the 3 μm~8 μm mid-infrared region using the finite -difference time-domain (FDTD) method. The influences of different geometrical parameters on the properties of SPSM-PCF are analyzed. All numerical computational results reveal that for the optimized geometrical parameters, the proposed PCF can deliver a SPSM region of more than 2.3814 μm with high nonlinearity of 3,705 w^?1 km^?1. Therefore, such a SPSM-PCF will become an excellent candidate for mid-infrared photonic.     

Optical fiber sensors

Abstract

Fiber optic sensors are finding increased usage in aerospace guidance and control applications due to their light weight, immunity to electromagnetic interference, high bandwidth and sensitivity, and solid-state, all-passive nature. This article reviews fiber optic sensors, with particular emphasis on aerospace applications.     

4 × 4 Plastic Optical Fiber Star Coupler Incorporated with a Common Polymer Waveguide Optical Power Distribution Region

Abstract

Two types of 4 × 4 plastic optical fiber star couplers incorporated with a polymer waveguide as the optical power distributor are proposed, and their high performances are demonstrated. The characteristics of the proposed star coupler are investigated based on ray optics, and its power distribution performance is evaluated in terms of the flatness of the coupling ratio and the amount of the excess loss. Under the best conditions, the flatness of the coupling ratio and the excess loss of the fabricated device have been obtained as 2.0 dB and 2.5 dB, respectively.     

Fiber optic data busses for aircraft

Abstract

A variety of fiber optic data busses is being developed for aircraft applications. This article addresses five different data busses under consideration for both military and commercial aircraft. The impact of data bus protocol on component design, the effect of data bus topology on power budget and installation issues, and overall data bus performance are discussed.     

Optical Fiber Communications: Recent Contributions in Photonic Device Technology

Abstract

The current status of the research and development as well as the recent contributions in optical communications at INESC Porto is reviewed. This review includes all the work carried out in the last few years in optical fiber communications, namely the development of passive and active optical devices. Some of the passive structures that have been studied and developed are: add-drop multiplexers, multiplexer/demultiplexer based on Bragg grating technology, dispersion compensators, and optical cross-connects. Active photonic devices such as wavelength converters, fiber lasers, and fiber amplifiers have also been studied. New ideas are being continuously developed and tested.     

Optical Fiber Sensor Technology in Portugal

Abstract

A general overview of the R&D activity in fiber optic sensing developed over the last fifteen years in Portugal is given. Different topics are addressed, including interferometric, intensity and Bragg grating based fiber optic sensors, signal processing and multiplexing techniques, optical current sensors, together with some references to field trials and applications. Possible guidelines for present and future national R&D activity on this subject are outlined.     

Performance of Distributed Fiber Raman Amplifier Based on Hybrid Cladding Photonic Crystal Fiber

Abstract

This article presents a feasibility study for using a hybrid cladding photonic crystal fiber as a distributed fiber Raman amplifier based transmission link with negligible confinement losses and flattened dispersion characteristics. The simulation results clearly indicate that a bit error rate of 10^?9 can be maintained at the end of a (4 × 170)-km distributed fiber Raman amplifier link operating with 40 Gbps and 0.6 dBm transmit power if 20 dBm of pump power is used for each span.     

Four-Mode Coupling in Fiber Bragg Grating Sensors Using Full Fields of the Fundamental Modes

Abstract

The four-mode coupling in shear-strain-loaded fiber Bragg grating sensors has been demonstrated to have influence on the measured spectra and, thus, on the application of embedded fiber Bragg gratings for strain field measurements. In a recent work, these coupling coefficients were derived using a set of assumptions on the properties of the fiber's modes. However, the validity of these approximations was not explicitly tested. Here, the required coupling coefficients are computed, making use of the full-field components. It is demonstrated that additional terms will appear; however, they are negligible in practical fibers, and thus, the made approximations are valid.     

Optical Solitons in Fibers for Communication Systems

Abstract

A brief history of attempts to use solitons for optical fiber communications and of the technical developments toward making soliton transmission practical is reviewed. The main problems affecting long-distance soliton transmission, as well as techniques to solve them, are described. Recent developments concerning the use of dispersion management and some of the remarkable properties of dispersion managed solitons are also discussed.     

3μm与2μm级联振荡Ho3+:ZBLAN光纤激光器的动态特性分析

基于传输速率方程，对Ho³⁺:ZBLAN光纤激光器的动态特性——上能级粒子数以 及输出激光功率的弛豫振荡特性进行了数值分析.通过忽略光纤参数对传输方向的依赖性，抽运光 和信号光的功率传输方程被分别简化处理.结果表明，在⁵I₆能级的 粒子数首先经历 一次弛豫振荡后，⁵I₆和⁵I₇能级的粒 子数交替弛豫振荡并达到稳态；同 样，在3μm波长的激光功率首先经历一次弛豫振荡后，3μm和2μm波长的激光功率交替弛豫 振荡并达到稳态，而且，弛豫振荡时的峰值功率远大于稳态时的激光功率. 关键词： 光纤激光器 动态特性 光纤激光理论 钬光纤     

Multiplexed ladar fiber-optic sensor system

Abstract

Practical considerations in the design of an optically multiplexed ladar fiber-optic linear-position sensing system are discussed, including network architecture, bus fiber count, fault location, sensor separation, and network efficiency. The results of a six-channel multiplexing experiment using a single laser diode are presented.     

Dual-Wavelength Erbium Fiber Laser in a Simple Ring Cavity

Abstract

By controlling the cavity loss of the modes using a variable optical attenuator, specific intensities of distributed modes can be fed back into the erbium-doped fiber to produce signals without mode competition, thus resulting in stable lasing as a means to overcome mode competition in a homogenous gain medium. Two lasing signals were obtained with peak powers of approximately ?3.475 dBm and ?4.386 dBm for wavelengths of 1,540 nm and 1,548 nm, respectively, with a side mode suppression ratio of more than 43 dB.     

An Overview of Mechanical Strength of Optical Fiber Fusion Splices: Examples of Fractographic Analysis of Break Causes

Abstract

The theory and phenomena of mechanical strength of fusion splices are reviewed. An emphasis is placed on fractographic analysis of break causes. A variety of useful examples of splice breaks resulting from surface mechanical damage, various types of contamination, re-deposition of silica particles/thermal shock, and devitrification are shown. Special strength reduction issues related to emerging new splice types and splicing techniques, such as arc fusion splicing of heat sensitive fibers, prolonged pre- and post-heat treatment (for reducing splice losses of dissimilar fiber splices), and fire polishing, are discussed.