Optimizing the thulium doped fiber amplifier (TDFA) gain and noise figure for S-band 16 × 10 Gb/s WDM systems

This paper aims to evaluate a comprehensive numerical model based on solving rate equations of a thulium-doped silica-based fiber amplifier. The pump power and thulium-doped fiber (TDF) length for single-pass thulium-doped fiber amplifiers (TDFA) are theoretically optimized to achieve the optimum gain and noise figure (NF) at the center of S-band region. The 1064 nm pump is used to provide both ground-state and excited state absorptions for amplification in the S-band region. The theoretical result is in agreement with the published experimental result.     

High-pressure and high-temperature generation using diamond/sic composite anvils prepared with hot isostatic pressing

Using a hot isostatic pressing (HIP) technique, we synthesized diamond/SiC composites from diamond and Si powders. At an HIP condition of 1450 °C and 100 MPa, a pressure much lower than that of the diamond stability field, diamond powders react with molten Si to form well-sintered diamond/SiC composites. Cubes of the composites with 15 mm edge length were thereby fabricated, and an application to the second stage anvils in a Kawai-type high-pressure apparatus was attempted. A hybrid anvils system using four cubes of the composites and four of the conventional WC was introduced and heating experiments up to 1600 °C became possible. Because the diamond/SiC composites are transparent to X-rays, the present system is applicable not only to diffraction studies but also to radiographic studies that need a larger window for an X-ray image.     

Adjustment of Residual Stresses in Unsymmetric Fiber-Reinforced Composites Using Genetic Algorithms

During the manufacturing process of multilayered fiber-reinforced composites with variable fiber orientations, residual stresses build up in these composites due to the directional expansion of single unidirectionally reinforced layers. Depending on the laminate lay-up, the inhomogeneous residual stresses, which are caused by thermal effects, moisture absorption, and chemical shrinkage, can lead to large multistable out-of-plane deformations. Instead of avoiding these curvatures, they can be advantageously used for technical applications following the near-net-shape technology. In order to adjust the deformations to the technical requirements, genetic algorithms in combination with a nonlinear calculation method have been developed, which can purposefully adapt the laminate lay-up depending on the loading and process parameters.     

Graphene Modified Lipophilically by Stearic Acid and its Composite With Low Density Polyethylene

Graphene, prepared by the thermal reduction of graphite oxide (GO), was modified with stearic acid to enhance its lipophilicity. A novel method, using the intrinsic epoxy groups on the graphene, was utilized for reaction with stearic acid to minimize the negative impact of the normal functionalization method on the π-electronic system of graphene. Gravimetric analysis, thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) showed that the stearic acid was effectively attached to the graphene. In addition, Raman spectroscopy and electric conductivity of the graphene showed that this novel modification method, utilizing intrinsic defects, did not damage the π-electronic system of the sp² bonded carbons. The dispersion of graphene in a low density polyethylene (LDPE) matrix was enhanced; consequently, the reinforcing effect in tensile testing was improved by the lipophilic modification. The crystallization behavior observed by differential scanning calorimetry (DSC) showed that the crystallization of LDPE was hindered by dispersed graphene, more evidently when dispersed uniformly.     

Design of Broadband L-band Erbium Doped Fiber Amplifier

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Thermoelectric and dielectric investigations of the thermochromism of various na-acetylacetonate phases and intermediates

Sodium acetylacetonate was prepared by the interaction of sodium metal with acetylacetone. A fresh sample and various samples preheated at various temperatures were carefully prepared. Measurements were made by x-ray diffraction, IR absorption spectroscopy and differential thermal analysis (DTA). The temperature dependence of the electrical and dielectric properties of selective batches of Na-acetylacetonate phase and intermediates was measured.     

Upconversion in Highly Doped Er3+-Yb3+ Fiber Pumped by Ti:Sapphire Laser at 800 nm

The up-conversion processes were investigated in highly doped Er3+-Yb3+ silica fiber pumped by CW or mode-locked Ti:Sapphire laser at 800 nm band. The mechanism is different from that at 980 nm pumped band. The pumping wavelength and power dependences of green, blue and red fluorescence emission were obtained. The up-conversion efficiencies of different doped concentration were investigated. The strong infrared emissions, which limit the efficiency of up-conversion were observed.     

掺铒光纤激光器中自脉冲的控制

在实验中观察到了掺铒光纤激光器中自脉冲，并通过加反馈的方法控制了自脉冲。在理论上利用带反馈的两激光器的耦合模型，成功地解释了自脉冲的产生及其控制的物理机制。结果表明，掺铒光纤激光器中两正交偏振态的反馈及其耦合对光脉冲的形成及控制的重要性。     

Measurement of Solid-gas Two-phase Flow using Optical Fiber Sensor

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Creep deformation measurement using quartz optical fiber

This paper describes an optical system for high temperature creep strain measurement using quartz optical fiber, super long working distance microscope and digital image processing techniques. In this system one end of the quartz optical fibers is arrayed in a small area on the specimen surface and the other end is illuminated by a laser beam. The fiber ends on the specimen surface form the spot array. The small optical spots on the specimen are tracked by a CCD camera and the images are processed by digital image processing software. The diameter of each quartz fiber is 100 μm and the fibers can be arrayed in a small area. The local strains are determined by measuring the variety of relative distance between two spots. Experimental results of local creep strain on the welding joints of 15CrMo and HK40 at 850°C are obtained.