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  4. No.40 January,2011
Fujikura Technical Review

No.40 January,2011



Silicon Photonic Device Based on Bragg Grating Waveguide
Silicon photonics has attracted considerable attention for fascinating features such as compact size, integration of various functional devices, and controllability by electronics. Bragg grating is used for various optical filters. One of the problems in the development of Bragg grating as silicon photonic device is birefringence of the waveguide. Therefore, we developed a new design of nonbirefringent waveguide. Furthermore, an inverse scattering method enables realization of a Bragg grating design for complex optical characteristics such as chromatic dispersion compensator (CDC). The development of a silicon photonic device using the nonbirefringent structure and the design by inverse scattering method is introduced.
Phase-Shifted Superstructured Fiber Bragg Grating
Optical code division multiple access (OCDMA) is one of the multiplexing access techniques that assign different codes to each user. It is one promising candidate for a new-generation broadband multiple access technique. In this report, we modify phase-shifted superstructured fiber Bragg grating (SSFBG) encoder/decoders. We also construct an optical network that uses multiport encoder/decoder at central office and SSFBG encoder/decoders at each ONU, and successfully demonstrate field trials of 10 Gbps×8 user DPSK-OCDMA system.
Fiber Fuse Phenomenon in Hole-Assisted Fibers
Optical fibers may be used in optical communication systems under high-power conditions in the near future. Fiber fuse will be a serious problem on the communication systems operated under high-power conditions. If the fiber fuse occurs, the core region of a fiber is destroyed catastrophically by optical discharge and the damage propagates along the fiber toward a light source. In this study, we investigate the threshold power of fiber fuse propagation on hole-assisted fibers (HAFs) and various kinds of all solid glass fibers.
Dispersion Compensating Fiber Module
Two types of slope compensating and dispersion compensating fiber (SC-DCF) are developed and fabricated into SC-DCF modules to impel the progress of dense wavelength division multiplexing (DWDM) transmission system, where there are two requirements for improving the performance of SC-DCF modules. The first requirement is to lower the insertion loss of the SC-DCF module in optical fiber transmission line. Low-loss SC-DCF module contributes to the relaxation in optical gain requirement of optical amplifiers, which improves the noise figure of the optical amplifiers as well as the overall performance of the optical fiber transmission systems. Downsizing of the SC-DCF module is the other requirement. DWDM transmission system consists of a large number of devices; thus, downsizing each device is one of the major developmental challenges. These two demands have different properties; thus, it is difficult to achieve both demands simultaneously. As a result, each of the new SC-DCF has been individually developed to meet these requirements. It is found that the newly developed SC-DCF modules have high performance for practical applications and will steadily replace conventional SC-DCF modules.
Optical Fiber Angle Cleaver
As the field-installable mechanical splice connector has a large reflection at the connecting point, it may not be advisable to use depending on the application. However, the amount of reflection can be reduced by connecting the angle cleaved optical fibers. Recently, as the use of the field-installable mechanical splice connector using angle fiber cleaves is increasing, the market demand for an angled fiber cleaver is also growing. To meet this demand, we have developed an optical fiber angle cleaver with consistent cleaving performance.
Optical Transceiver for 10G-EPON Dual-Rate OLT
The 10Gbit/s Ethernet Passive Optical Network (10G-EPON) system is actively being developed in order to satisfy the future bandwidth demand of broadband subscribers. In a market like Japan where currently 1Gbit/s EPON (1G-EPON) has been widely deployed, 10G-EPON Optical Line Terminals (OLTs) equipped with 1G and 10G dual-rate burst mode optical receiver are preferred. We have developed a burst mode optical transceiver that incorporates not only the dual-rate burst mode receiver, but also both 1G and 10G transmitters in one package, and have also confirmed excellent characteristics.
Mounting Technique of 0402-Sized Surface-Mount Device (SMD) on FPC
A reduction in the size of surface-mountable passive devices from current 0603 to 0402 is expected as electrical appliances are miniaturized. Flexible printed circuits (FPCs) are used in electrical appliances equipped with three-dimensional wiring boards on which various surfacemount devices (SMDs) are soldered. With this being the situation, we established a series of constituent technologies from pattern designing to reflow soldering processes to achieve the mounting of 0402-sized SMDs on FPCs.
One-millimeter Heat Pipe and Application to Cooling Module for Electronic Devices
Electronic devices are becoming compact with enhanced performance. Therefore, it becomes a challenging task to provide the cooling solutions for these compact devices with high-density heat generation. Regarding this challenge, thin flat heat pipe can play a vital role. In the present study, experimental investigation of the thin flat heat pipe with a thickness of 1.0 mm has been performed. In this paper, different kinds of new fiber wick structures consisting of a combination of copper fine fibers and axial grooves are investigated. Thin heat pipe having these new wick structures showed highly improved thermal performance as compared with that having normal wick structures. The effect of length, thermal test mode, and bending on the thin heat pipe thermal performance has been studied. From the present study, it is found that maximum heat transfer capability of the present 1.0-mm-thin heat pipe is 11 W, with the thermal resistance of 0.6 °C/W. Bending has reasonable effect on the thermal performance of heat pipe. Besides, thermal performance of remote heat exchanger fabricated by using the developed thin heat pipe has been investigated. Twenty-five watts of heat can be transferred by using the present assembly.
Polylactic Acid-Coated Cable
The polylactic acid (PLA), which is a plant-derived polymer, is an environment-friendly polymer from the point of view of not only having biodegradable property but also saving fossil resources and reducing carbon dioxide emission. Although the PLA has already been applied to many products, it has not yet been applied to cable. Thus, we manufactured and tested the cables using normal and flexible PLA, so as to identify the possibility and problem of application of PLA insulation to cables.
Carbon Nanotubes Counter Electrode for Dye-Sensitized Solar Cell
The counter electrode of the dye-sensitized solar cell plays a role in reduction of the electrolyte that oxidized at the photovoltaic electrode. So far the counter electrode has used platinum from the perspective of reduction capability and corrosion resistance to the electrolyte. However, the material of a high corrosion resistance and low cost has been demanded because platinum still has issues of the insufficient corrosion resistance to the iodide electrolyte and of cost. The carbon materials are potential candidates to solve these issues. Thus, we have developed carbon nanotube owing to its attractive characteristics. We report the development of an electrode of a superior reduction capability with the carbon nanotubes that are utilized as the counter electrode of the dye-sensitized solar cell in this study.
True Three-Dimensional Interconnections
As one of the next-generation through-hole interconnection (THI) technologies, true three-dimensional interconnections (True3D interconnections) such as crank-shaped or Y-shaped THI have been developed. As an arbitrary electrical interconnection can be formed in a substrate using this technology, a higher-density and more design freedom electric device package can be expected compared with the conventional THI having straight shape. In this study, the fabrication method and the structural and electrical properties of the True3D interconnections are reported. An interposer sample with the True3D interconnections is also mentioned.