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R & D Review


No.96 February 2000

Ecological Wires and Cables, and Life Cycle Assessment

Recently, environmental problems have spread to a global scale, e.g., global warming and ozone depletion, from local air pollution and area acid rain. Various investigations and actions are taken to reduce environmental loads in many fields.
From this point of view, the authors have developed ecological wires and cables, ECOSAFE(TM), that contribute to reduce environmental loads when they are scrapped.
On the other hand, it is important to understand the exact effect of products on the environment. Presently, life cycle assessment (LCA) is proposed as a tool which is possible to make scientific, quantitative and objective estimation on the environmental loads of products through its life cycle. Guidance on LCA’s use is now published by ISO (14001s).
In this paper, the activities to reduce the environmental loads of wires and cables is discussed based on the results from LCA of the ecological wire at each stage of the life cycle, i.e., raw materials, manufacturing and operation process.
Consequently, it is found that the followings affect the environmental loads :

  • amount of filler such as flame-retardant
  • extruding processability
  • recyclability

The improvement of the above is important to reduce environmental loads. Application of LCA on other types of wires and cables is significantly useful to develop the materials and products in consideration of the environment.
[Key words] Halogen-free, Flame-retarding, Ecological material, Life cycle assessment, LCA, Environmental load, Environmental problem

Flexural Rigidity and Axial Snaking Force of XLPE Cable

XLPE insulated cables have been used in the rated voltages of 22kV and 33kV for 35 years, since 1960. In the year 2000, 500kV XLPE cable lines will be put to commercial use. This trend to extra-high voltage of XLPE cable whose most significant feature is dielectric superiority and being oilless, is due to the technical progress in manufacturing and quality control of cable and joints, and the result of systematic progress including installation design method against expansion and contraction of cable. The authors carried out a study on snaking installation of single core XLPE cable which is an effective measure against the expansion and contraction of cable installed in tunnels, and found that the repellent force after snaking work is comparatively large and remains as residual tensile force in heat cycle. By considering these phenomena, the correction formula of calculating axial force are proposed and was testified to be accurate enough in comparison with the measuring result. Theoretical formula of axial force generated in various installation method including vertical snaking not applied for OF cables are also proposed not only considering the bending deformation but also considering the cable weight itself. As aresult, a simple formula applicable for practical use are proposed by arranging the various factors. Moreover, the experimental formula of flexual rigidity is conducted by arranging the theoretical method. From the above results, the difference between horizontal and vertical snaking is clarified, and the axial force can be simply and practically calculated.
[Key words] XLPE cable, Strain in bending, Flexural rigidity, Snaking installation, Axial snaking force

Development of Cold Shrinking Tube-type Indoor Termination and Straight Joint (MINICONE® QUICK Series) for 6600V XLPE Cable

Taping-type, insertion-type and heat shrinking tube-type termination and joint have been used extensively for 6600V XLPE cable. However, these types all have problems like lacking safety due to the use of fire or requiring certain skills for the assembling work.
The cold shrinking tube-type indoor termination and straight joint for 6600V XLPE cable were developed to improve these problems. The assembling work of the developed termination and joint is very easy in comparison with the usual type, the number of parts were decreased, and the size was reduced. Sufficient long-term reliability has been confirmed by the success of development tests.
[Key words] Cold shrinking tube-type, Improvement of the assembling work, Compact accessories, Silicone rubber, Solderless

Development of Layer Short Checker for Winding of Low-voltage Compact Motor Coil

Low-voltage compact motors are widely used in various electric machines. Coil windings of low-voltage compact motors are rarely layer shorted during the manufacturing process. Such motors with layer short are thermally troubled in prolonged operation. We have developed the Layer Short Checker for Winding of low-voltage compact motor using reverse electromotive force which appeares when DC current of winding is removed. The Layer Short Checker has equal detection performance of that of traditional impulse checker. In addition, it is safe because it dose not use high voltage circuit.
[Key words] Low-voltage compact motor, Layer short, Impulse tester, Reverse electromotive force

New WF-H Coaxial Cables

More then fifteen years have passed since WF-H coaxial cables were developed. Through the quick spread of cellular phones (a typical of Mobile Communications Systems) in recent years, the demand of WF-H coaxial cables used as a feeder cable in the base station for cellular phones are increasing. An active demand for the phones is estimated because the new cellular phone service will start in 2000 A.D. by IMT-2000 system.
Severe requirement for the quality and characteristics of the cables are expected than ever before, especially for the attenuation.
We have developed a new type of WF-H coaxial cable having lower attenuation and minimized cable diameter.
In addition, we have improved the connector handling by reducing the connector dia. and have achieved a dust- tight and waterproof connector with high reliability (to meet IP68-IEC 529 requirements). IMD characteristics presents the lowest value among competitors in the world by an original low IMD connector design.
[Key words] Mobile communications systems, Cellular phone antenna base station, IMT-2000, Attenuation, IMD

Improvement of Highly Expanded Insulation Material for Low Loss Antenna Feed Coaxial Cable for Mobile Communication in Base Station

Highly expanded insulation materials for coaxial cables are composed of blowing agent, nucleating agent and base polymer. After many improvements , coaxial cable with highly expanded insulation material using no fluorocarbon from the view point of environmental protection was found to be appropriate for practical use. Recently with the increase of requirments for superior properties of attenuation constant by small-sizing of antenna feed coaxial cable for mobile communication in base stations and rising of frequency band for next generation handy phone system, the expanded insulation must be improved. In this paper as a result of study on the constituent materials of expanded insulation (blowing agent, nucleating agent and base polymer), we have developed a new cable with lower attenuation (11 ~ 19%,at 2GHz) than the conventional cable by selecting the materials with excellent tanδ properties at high frequency band.
[Key words] Base polymer, Blowing agent, Mobile communication systems, Expanded insulation, tanδ, High frequency, Attenuation

Development of Digital Controlled High-Function Optical Fiber Amplifier (FA155D)

With the development of high speed and large capacity optical communication technique, demands for such EDFAs that show wide bandwidth, high power output, low noise figure, constant gain-wavelength property, low polarization dependence and so on have been increasing remarkably.
In this paper, we report on our newly developed CPU controlled EDFA (type FA155D) suitable not only for laboratories but for general applications.
Digital display of this EDFA show the output power of the amplifier and pre-set values inputted using rotary knob and function keys. Multi pumping LDs of the high power amplifier can be controlled individually.
Typical properties of the EDFA (FA155D-25) are as follows :

  • Saturated optical output power     more than 300mW
  • Small signal gain at 1550nm     more than 35dB
  • Noise figure (input signal power -10dBm)     typical 7dB

[Key words] Optical fiber amplifier, EDFA, Er-doped fiber, EDF, CPU

Broadband and Gain-flattened Erbium-doped Fiber Amplifier for L-band Amplification

The erbium-doped fiber amplifier (EDFA) is a key device for high capacity wavelength division multiplexing (WDM) optical communication systems. High density WDM transmission system using an EDFA requires more multiplexed channels. Therefore researches to expand an amplification bandwidth towards a longer wavelength side, so-called L- band, has been investigated.
We have demonstrated a gain-flattened EDFA which has two stage amplification units connected by an optical isolator. The first unit is forward-pumped by 1.48 µm LD and the second one is backward-pumped by 1.48µm LD.
When the input power is - 10 dBm and a product of Er concentration and erbium-doped fiber(EDF) length of each EDFA unit are 8 kppm · m and 100 kppm · m, 1-dB gain band from 1560 to 1606 nm was achieved. Signal output power of more than +20 dBm was obtained in a wavelength range from 1560 to 1607 nm.
With regard to power conversion efficiency, 50 ~ 60 % was obtained in the wavelength range within 1-dB gain bandwidth.
We also measured a four channel amplification characteristics. When the signal wavelengths are 1570, 1580, 1590 and 1600 nm and signal power is -16 dBm per channel, output power of each channel were 15.9, 15.9, 16.6 and 15.7 dBm and their deviation was ± 0.45 dB.
[Key words] Eribium-doped fiber, Optical fiber amplifier, WDM amplification

Strain Distribution Measurement in Optical Cables using Multi-pointed Fiber Bragg Gratings

Strain distribution along an optical fiber inside cables were optically measured by placing fiber Bragg gratings (FBG) with different reflecting wavelengths on the fiber. As a method for controlling the reflecting wavelength of each grating, various tension was applied to the fiber during UV exposure. We controlled the Bragg wavelength for 17nm (approx. 1.4% tension) with a single mask. Gratings were fabricated at regular intervals on a fiber for a slot type optical-fiber cable. The strain distribution induced by bending the cable was observed. Distribution measurements in a spatial resolution of 50mm, strain measurement precision of 0.002% was possible. We confirmed a strain distribution responding in accordance to the structure of the fiber locus inside slot type cables. The sensing fiber with multi- pointed FBGs has the same mechanical strength as normal fibers by UV exposed over the coating. Sensing fibers can be used in the cabling process and also in traction and installation.
[Key words] Fiber Bragg grating, Strain distribution, UV exposure over the coating

A Study on UV-Transparent UV-Curable Resin for Fiber Bragg Gratings Written through a Fiber Coating

Fabrication of fiber grating without removing the coating prevents degradation of fiber strength and simplifies the manufacturing process. As a coating material suitable for irradiating through the coating with good productivity, we investigated an aliphatic urethane acrylate UV (Ultraviolet) curable resin with improved transparency. We evaluated the transparency, mechanical characteristics, long-term reliability of the resin and the properties of the coating before and after UV laser irradiation, and confirmed the new resin to have the good characteristics and reliability adequate as the coating for fiber gratings.
[Key words] Fiber grating, Aliphatic urethane acrylate ultraviolet curable resin, Transparency, Long-term reliability, Young’s modulus, Elongation

Development of GaN Semiconductor

Highly efficient white-light-emitting diodes (LEDs) fabricated from red-green-blue phosphors and ultraviolet (UV) LEDs are expected to be superior to those fabricated from yellow phosphors and blue LEDs as light sources for illumination, on the basis of their color rendering properties. However, UV LEDs are more sensitive to dislocations in the epitaxial layer than blue LEDs. To improve the emitting efficiency of UV LEDs, the relationship between the photo-luminescence (PL) wavelength of the active layer for LEDs and the PL intensity was investigated. The PL intensity is reduced when the PL wavelength becomes short. This indicates that the emitting efficiency of UV LEDs is sensitive to dislocations in the epitaxial layer. Therefore, the relationship between dislocation density and PL intensity was investigated. An increase of the PL intensity was observed with a reduction in dislocation density. These results indicate that the reduction of dislocation density is effective for increasing the efficiency of UV LEDs. The epitaxially lateral overgrowth (ELO) technique was carried out to reduce the threading dislocation density. Using the ELO technique, the number of threading dislocations was reduced by approximately two orders of magnitude. Therefore, it is considered that high-efficiency UV LEDs can be fabricated using the ELO technique.
[Key words] White light-emitting diodes, GaN, Dislocation, Epitaxially lateral overgrowth

Development of Optical Parametric Oscillator Using Periodically Poled MgO-Doped LiNbO3 Crystal

A 0.5-mm-thick periodically poled MgO-doped (5 mol%) LiNbO3 (PPMgLN) crystal with domain-inverted periods of 26.2~32.0µm and an interaction length of 30 mm was successfully fabricated by an electric field poling process. The average ratios of the domain-inverted width to the domain-inverted period (duty cycle) were approximately 50%. For the first time to our knowledge, quasi-phase matching (QPM)-optical parametric oscillation (OPO) using a PPMgLN crystal was demonstrated. During QPM-OPO, the PPMgLN crystal exhibited a higher resistance to photorefractive damage than did a periodically poled LiNbO3 (PPLN) crystal. OPO properties of the PPMgLN crystal at 20°C were comparable to those of a PPLN crystal heated to 95°C to prevent photorefractive damage; this enables operation in the steady state at room temperature. The QPM-QPO device using a PPMgLN crystal is thought to be widely used as a compact tunable infrared (IR) source and an optical wavelength conversion in laser application. These QPM devices and employing techniques is expected to make possible remote-sensing systems and wavelength division multiplexing (WDM) optical-communication systems.
[Key words] Periodically poled MgO-doped LiNbO3 (PPMgLN), Electric field poling process, Duty cycle, Quasi-phase matching (QPM), Optical parametric oscillation (OPO), Photorefractive damage

Investigation on the Wear Characteristics of Polytetrafluoroethylene (PTFE) Composites for Seals

Polytetrafluoroethylene (PTFE) composites that filled various materials have been used as a material for dynamic seals. Machines today tend to operate under high pressure and high speed, so severe specifications are required of seal materials. It is believed that seal life can be increased by improving wear resistance and extrusion resistance.
We investigated how wear resistance and limiting PV value changed by the fill material could satisfy such a requirement. As a result, we were able to confirm that the PTFE with bronze or a heat-resistant plastic additive had excellent effect on wear resistance and limiting PV value. On the other hand, material filled with the fiber had little effect.
In this paper we show how wear resistance and limiting PV value changed by different kinds of the fill materials. We will research in detail about the effect of the fill material’s form, size, and physical properties in the future.
[Key words] polytetrafluoroethylene,filler ,wear,limiting PV value

Development of High Performance Thermoplastic Rollers

Along with the technical progress to pursue higher speed performances of OA machines, photo printers and other applications, marketing requirements for rollers with longer length are increasing. Reinforcing of the current thermoplastic rollers is necessary due to insufficient bending strength in longer lengths.
Our technical trials to reinforce the thermoplastic rollers were made by inserting metal cores into extrusion molded pipes. Development of the optimum production procedures was also completed. Because the applied thermoplastics for rollers have variable thermal expansion properties, the inserting procedures established use two kinds of heating systems with the optimum precious extrusion conditions depending on the thermal expansion coefficients. This report summarizes the production procedures and other new technology.
[Key words] Thermoplastic roller, Thermoplastic resin, Metal core, High frequency induction heating, Extrusion mold, Thermoplastic elastomer

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