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R & D Review


No.99 July 2002

Photonic Crystal Fibers(1) - Optical Properties -

The cladding of Photonic Crystal Fiber (PCF) is constituted of air holes arranged as periodically as the wavelength of light in the silica glass. The cladding having a structure made up of silica glass and air holes enables characteristics that are quite different from those of conventional fibers. In this paper, we introduce the outline of fabrication and structure of PCF and explain dominant optical properties of PCF compared with those of conventional step index fibers.
[Key words] Optical fiber, Photonic crystal fiber, Single-mode fiber, Fiber characterization

Development of Heat Resistant UV transmission Optical Fibers

When optical fibers are exposed to ultraviolet radiation (UV), transmission loss occurs in the Deep Ultraviolet radiation (DUV) region. In recent years, available wavelengths in the ultraviolet has expanded to the DUV region but the above transmission loss has become a problem.
We have developed a heat-resistant optical fiber with enhanced UV resistance in the DUV region and evaluated its UV resistant characteristics after heavy hydrogen lamp and ArF excimer laser exposure.
During 1,000 hours of exposure under heavy hydrogen lamp (0.21mW/cm2 @250nm), the variation rate of the transmitted quantity of light was maintained at 70% (when initial value was 100%), indicating much improvement. Under ArF excimer laser exposure (12mJ/cm2/pulse), the variation rate of the transmitted quantity of light was approximately 54% at 1.2 × 107 pulses.
[Key words] Optical fiber, Ultraviolet radiation, Ultraviolet radiation resistant, Excimer laser, UV, DUV

Development of Optical Fiber Amplifiers (FA155E)

In the fields of high-speed optical communication, optical amplifiers are now indispensable, because of the spread of DWDM (Dense Wavelength Division Multiplexing) systems. We have been developing various kinds of rare-earth element doped fibers such as Erbium doped fibers (EDF) or Neodymium doped fibers (NDF) and fiber amplifiers and ASE (Amplified Spontaneous Emission) light sources. Recently requirements for small size optical fiber amplifiers are also pressing.
In this paper, we report on CPU controlled compact size optical amplifier modules (FA155E series) best suited for built-in applications. The FA155E series have the following features.

  • Applicable as Pre-amplifiers and Post-amplifiers
  • Two kinds of standard FA155E are available ;
    13dBm and 16dBm saturation optical output power
  • Compact in size, 120(W) × 16(H) × 80(D) mm
  • Automatic Level Control (ALC) and Automatic Current Control (ACC)
  • RS-232C (point to point), RS-422 (point to multi-point) interface
  • Pump LD current and alarms are programmable and can be monitored from outside of the PC
  • Two stage alarm on pumping LD
  • Single working voltage of DC+5V

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

Development of a 7kW Pulse Light Source for Single Mode Fibers Having 1.55µm Band Output

In recent years, the quantity of information to be transmitted through optical fibers is growing, increasing the use of the wavelength division multiplexing (WDM) system. In an WDM transmission, transmission lines and optical parts are more likely to be damaged by the increase of the optical power from the pulse beams brought on by the large quantity of information, compared to conventional fiber transmission. Presently, reliability of the damaged optical parts is evaluated by inducing W level continuous wave (CW) laser beam. However, the evaluation for a single unit is time consuming, making it impossible to evaluate the entire system. To solve this problem, a high power pulse light source was developed as a light source apparatus for accelerating the generation of optical damage. For the high power pulse light source, pulse amplifying characteristics of erbium-doped fiber amplifier (EDFA) was conveniently used. The gain recovers around the generation of the pulse when a repeating pulse beam which has had ample recovery time is induced. This enables the generation of a pulse beam having peak power at the kW level. This high power pulse light source also uses optical band pass filter (OBPF), polarization controller (PC), and a new optimized EDF structure to enhance the peak power.
The OBPF eliminates amplified spontaneous emission (ASE) generated between pulses in the first EDFA. Therefore the ASE amplification between pulses in the second EDFA is subdued, enabling a sufficient inverted population state. The PC controls the polarized light of a signal beam from the second EDFA output which generates high peak power. By controlling the state of the polarized light, nonlinear optical effects can be suppressed which is the cause for weakening the peak power of the signal beams around the second EDFA output. The new structure EDF uses enlarged mode field diameter (MFD) to suppress the nonlinear optical effect. With the enlarged MFD, optical pulses with equal peak power can be transmitted at a lower power density than conventional EDFs, suppressing the nonlinear optical effect in the EDF.
By applying the above improvements of OBPF, PC and new structure EDF, the high power pulse light source introduced in this paper has succeeded in achieving a maximum 7kW peak power. Additionally, this high power pulse light source is a transverse single mode output from a single mode fiber which allows a high quality M2≈1 beam that can be made to have high convergence characteristics. This makes the light source ideal to be used not only in reliability evaluations for accelerated tests but also in micro machining metallic surfaces. Furthermore, the eye safe 1.55µm bandwidth signal beam allows such uses as in laser range finder and in laser radar.
[Key words] WDM, EDFA, High power light source, Nonlinear optical effect, Amplified spontaneous emission (ASE), Mode field diameter (MFD)

Development of Optical Drop-Cable Suitable for Wiring Through the Conduit Run (Sewer System, Buildings, etc.)

As demand for high-speed Internet increases, the use of FTTH (Fiber To The Home), capable of high-speed and large-capacity transmission is rapidly diffusing. As one of the means to realize FTTH, techniques for using sewage systems have been developed.
We have developed thin, light and flexible loose tube type optical drop cables that are suitable for wiring in conduits and most appropriate for FTTH using sewage systems.
The loose tube type optical drop cables can be used not only for wiring in conduits, but also for indoor LAN (Local Area Network) wiring when multi-mode fibers are used as housed core wires and flame-retardant polyethylene sheaths are used for cable sheathing.
[Key words] FTTH, Wiring through conduit run, Drop-cable, Loose-tube

Development of Wavelength Converter Based on Quasi-Phase-Matched PPMgLN Waveguide

We demonstrated C-L band wavelength conversion based on Quasi-Phase-Matched (QPM) PPMgLN waveguide. Cascaded nonlinear wavelength conversion was confirmed by using the PPMgLN waveguide with Grating period of 17.4µm, length of 30mm at room temperature. Conversion efficiency of -7dB was obtained for C-L band conversion at the pump power of 43dBm (24W) pulse.
[Key words] Quasi- Phase- Matching, PPMgLN waveguide, Optical communication, Wavelength conversion, C-band, L-band

Development of White LED Fabricated by RGB Phosphor and Near Ultra-Violet LED

White light-emitting diode (LED), which consists of an InGaN-based blue LED and yellow fluorescent phosphor is already in practical use. The white LED made by a new technology of combining the near ultra-violet (NUV)-LED and fluorescent phoshor of the three primary colors (red (R), green (G), blue (B)) is promising for use in lighting. The white LED emitting three primary colors can have the high general color-rendering index and have a variety of color temperature. MITSUBISHI CABLE INDUSTRIES, LTD. has developed the new growth technique called LEPS (Lateral Epitaxy on a Patterned Substrate with stripe grooves), and applied it to fabricate the NUV-LED. Furthermore, jointly with STANLEY ELECTRIC CO., LTD, MITSUBISHI CABLE INDUSTRIES has experimentally fabricated the white LED with RGB phosphor and the NUV-LED as an excitation light source. As a result, due to the LEPS method, the dislocation density of GaN layer has been reduced to approximately 1.5×108 cm-2, the output power of the NUV-LED was 15.6 mW, and the external quantum efficiency was approximately 24% (emission peak wavelength: 382 nm; flip-chip mounted; at room temperature; forward current: 20 mA). The properties of the white LED using this NUV-LED were as follows: the luminous efficiency of 8.2 lm/W, general color-rendering index of Ra= 86~90, and color temperature of 6900 ~ 7600 K (at room temperature, forward current: 20 mA).
[Key words] GaN, LED, NUV-LED, White-LED, Phosphor, LEPS

The Recyclability of Ecological Cables

In the case of electrical wires and cables, the recycle ratio of copper and aluminum are almost 100%. But the recycle ratio of plastic materials e.g. sheaths and insulators, are less than half, the rest is buried underground.
Ecological cables were developed as products which can be recycled easily, but none have been recycled so far as it is only three years since the development of the cables; too early for a cable lifetime to finish.
Therefore in order to investigate the recyclability of ecological cables as jackets of new cables, we made sample sheets with similar conditions of a cable jacket that finished its lifetime by accelerated weather-proofing tests.
As the results of the measurement of physical properties and electrical properties, we found that the jacket materials of cables which finished their lifetime can be used for insulators of new cables.
For a useful recycling systems for ecological cables, it is necessary to find practical methods for each process e.g. separation of materials, removing contaminations.
[Key words] Recycle, Ecological cable, Weather-proof, Polyethylene, Polyvinyl chloride

Development of a High Voltage Power Supply System for Tunnel Boring Machines

Tape-wrapped joints have been mostly used in high voltage (6600V) power supply cabling system for Tunnel Boring Machines at tunnel construction site. It requires certain skills, workmanship and the joint assembly is time consuming.
To meet the demands of shortening and simplifying the joint assembly time at the site, we have developed the 6600V cable joint connector using a pre-molded-insulator and cable handling system. We have succeeded in realizing cost down, short assembly time and simplifying of the joint assembly.
This report describs the development of a high voltage power supply system. This new system produced actual results in the mountainous Hida tunnel and the Shimura-Sakashita utility tunnel at an urban under ground site.
[Key words] Tunnel boring machine, 6600V Power supply system, High voltage cable connector, T-type joint, Cable handling system, Cost down

Development of Communication Testing Device for Inductive Radio

There is a space wave (VHF radio) form and an electromagnetic induction (inductive radio) form of inducing lines for communication between moving trains, and terrestrial stations.
As one of the causes for changes in the longitudinal direction in the magnetic coupling is electromagnetic induction generated by nearby electric wires and ladders with transmitting signals which shields the induced line (such as antenna).
Therefore, we developed a receiver which detects signals induced by the inductive radio (150kHz ~ 200kHz) in electric wires and ladders and confirmed its performance.
[Key words] Inductive radio, Electromagnetic induction, Inducing line, Receiver

Completion of the 400kV Polypropylene Laminated Paper Insulated Oil-filled Cable Project in Singapore

In June 1999, MITSUBISHI CABLE INDUSTRIES, LTD. was awarded a full turnkey contract by PowerGrid Ltd., Singapore for the supply and installation of a 400kV polypropylene laminated paper insulated oil-filled power cable system between Tuas power station and Ayer Rajah substation, of which was materialized with the aim of stable power supply against the increasing electricity demand in Singapore.
The cable system composed of 24km of double circuits (6 cables) with communication optical fiber cables (24 cores×6 cables, 36 cores × 2 cables) including alarm cables (20 cores × 2 cables) for monitoring of the oil pressure of the power cable system.
In addition to these power and data transmission systems, Distributed Temperature Sensing System (DTS) was applied on the surface of the power cable to monitore temperature profiles during operation.
Prior to the manufacturing, the 400kV polypropylene laminated paper insulated oil-filled power cable and the relevant cable accessories were type tested in the presence of the client and their consultant at our Kumagaya factory in accordance with IEC standards and NGTS standards (Power Company Standards in UK) and passed satisfactorily.
Throughout the contractual period, all activities relating to the contract were severely controlled by ISO 9000 quality control system, such as design, delivery and transportation, local civil and electrical works, not to speak of the manufacturing of materials.
Thanks to these well controlled quality system and full-fledged technical ability and through the good offices of the personnel concerned, the project was completed and energized in August 2001 within the contractual period, only after 26 months from the award of the contract.
[Key words] Polypropylene laminated paper, NGTS standards, 400kV Oil-filled cable, Shock watch, Residual gas test, Particle count test

Development of The Sheet-Type Electromagnetic Wave Absorber for ETC/DSRC

DSRC (Dedicated Short Range Communication), which is a communication system for high-speed transportation, uses microwave of the 5.8 GHz band and has been used as ETC (Electronic Toll Collection) for the public since 2001. In the near future the DSRC is expected to expand into various private fields. Under such circumstances, the wave absorber which adjusts the electromagnetic environment and secures the reliability of communications will be applied to various places in many forms.
We have developed wave absorbing panels for the canopy of tollgates on the expressway which are installed all over the country. Many kinds of the wave absorbers are necessary for various installing situations (e.g. curved surfaces, small and complicated places).
This report describes the development of a thin sheet type wave absorber suitable for these situations. Our sheet type wave absorber designed by transmission line theory and for use under the circularly polarized wave realizes absorption performance which meets ETC specifications by JHRI (Japan Highway Public Corporation Research Institute) at only 1.9 mm in thickness. Furthermore, it is very flexible and easy to cut into any size or shape, so it can be used for any purpose. We expect that our sheet-type wave absorber will contribute to the early realization of the DSRC system.
[Key words] ETC, DSRC, Electromagnetic wave absorber, Transmission line theory, Circularly polarized wave

Development of Adhesive Technology for PTFE on Metal Substances
- Surface Modification of PTFE by Plasma Etching Treatment -

Polytetrafuluoroethylene (PTFE) is widely applied to many industrial products because of its excellent combination of thermal, electrical and mechanical properties as well as chemical resistance. The low surface energy which forms the backbone of the stable polymer chain exhibites difficult adhesion to other substances requiring surface pre- treatment such as chemical etching before adhesion.
Current pre-treatments of PTFE surface include chemical etching by naphthalene-sodium solution and other chemicals. However, a substitute treating procedure for chemical etching is required to protect the environment.
On the other hand, epoxy based adhesives are widely used with PTFE, and possess relatively strong adhesive strength after chemical etching. However, the lower heat resistance of epoxy adhesives compared with that of PTFE limits the operating temperature of its products. An adhesive agent with higher thermal stability is required to solve this problem. Both the improvement on thermal stability of adhesives and the surface pre-treatment procedure instead of chemical etching were investigated in order to establish the appropriate technology for adhesion of PTFE on metallic substances.
Consequently, the polyimide based adhesive modified with epoxy resin which had suitable affinity to PTFE were improved to resist up to 200°C. Furthermore, plasma treatments onto PTFE surface in argon gas was found to increase the adhesive strength more than the conventional treatment of naphthalene-sodium solution. The SEM (Scanning Electron Microscope) analysis clarified that the effect of plasma irradiation on PTFE adhesion depended upon an "anchor effect" by roughing the surface of PTFE. In addition, it was found that optimum conditions such as reactive gas pressure, temperature and others existed for plasma pre-treatment of PTFE to obtain satisfied adhesive strength.
[Key words] Fluorine resin, Polytetrafuluoroethylene, Adhesion, Heat resistance, Polyimide resin, Epoxy resin, Plasma, Argon, Surface modification, Etching, Anchor effect, Surface analysis

The Development of High Performance Compressor Seal for Car Air Conditioners

The Shaft seal is used for sealing refrigerants and lubricant oils in the compressors of car air conditioners. Along with environmental problems and trend to smaller and lighter compressors, operation conditions have become more severe year by year. The seals have been improved for higher speed, pressure and temperature.
This paper reports on the technical characteristics of higher performance Sunflon® RL seal, and various sealing parameters for the shaft seals of car air conditioner compressors.
[Key words] Car air conditioner, Compressor, Shaft seal, PTFE

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