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64 Feature Articles: Optical Fiber Communications pared with the step index profile. As an example, simulated and measured bending loss at 1650 nm as a function of bending radius for fibers with the trench-index and step-index profiles Fig�� Fig�� Fig�� Fig�� Fig�� Simulated Simulated Simulated and and measured measured bending bending loss loss at at ��nm ��nm ��nm ��nm ��nm as as a a func� func� func� func� func� tion tion of of bending bending radius radius for for for fibers fibers with with trench�index trench�index trench�index trench�index trench�index and and step�index step�index step�index step�index step�index profiles� profiles� profiles� profiles� profiles� are shown in Fig.7. The bending loss of the fiber with a trench index profile is lower than that of the fiber with a step index profile. A mechanical splice loss between the fiber and C-SMF is 0.15 dB in average and 0.03 dB in standard deviation, which is acceptable for practical use. V. EASY-HANDLING Ø0.5 -MM OPTICAL FIBER It has been necessary to simplify the installation of cables and to reduce construction time to popularize FTTH. A fiber with thicker coating than the conventional fiber with a diameter of 0.25 mm is expected to ease the handling in installation and connection. However, commercially available connection tools and devices for FTTH are specialized for Ø 0.25-mm fiber. The schematic of structure for the easy-handling Ø0.5-mm optical fiber is shown in Fig.8. Two layers of UV curable resin and a thin layer of colorant are applied to Ø0.125 mm silica fiber, and the outer diameter of this fiber is Ø0.25 mm. The low-bending-loss single-mode fiber (FutureGuide ® -SR15) is employed as the silica fiber in order to reduce bending radius in storage and loss. The outer surface of this fiber is coated with colored UV curable resin, and the final diameter is 0.5 mm. This layer is designed to be easily strippable from the Ø0.25-mm fiber but to be stably attached to the fiber. As a result, the existing commercially available splice tools and devices can be applied to the new fiber. The characteristics of Ø0. 5mm optical fiber are shown in Table 3. VI. DROP CABLE In Japan, the typical drop cable wired from an aerial Fig�� Fig�� Fig�� Fig�� Fig�� Schematic Schematic Schematic of of the the structure structure for for Ø�� mm mm mm optical optical fiber fiber in� in� in� in� in� crease crease in in handling� handling� handling� handling� handling� China Communications December 2005
decreasing the number of manufacturing process and reducing the cable diameter. For easy installation, the cable has been designed so as to take the fiber out easily. The Ø0.5-mm optical fiber described in the previous section also will be employed in the cable. The cable can be separated off the supporting wire without special tools thanks to the notch between the supporting wire and the cable in order to improve the handling for the installation. In addition, the fiber can easily be taken out the cable thanks to the notch Feature Articles: Optical Fiber Communications Table.3 Characteristics ofØ0.5-mm optical fiber. in the center of the cable. Central value The cable size has been reduced to 5 mm Attenuation 1.31 µm 0.340 dB/km 2 mm. The strength member is made of 1.55 µm 0.193 dB/km the plastic material. The sheath has good Handling property flame-resistance and reduced environmental burdens by employing non-halogen material. VII. AERIAL CABLE Aerial cables are popular in Japan. The length of an aerial cable on one drum should be elongated to reduce connection points of the cables for installation cable to a subscriber contains one optical fiber as cost reduction. In addition the cable should be shown in Fig.9. The drop cable has been designed in consideration of cost reduction and easy installation. The cost reduction of the cable has been achieved by light in weight for easy installation. The key points of the cable design are described as follows. [13] 1.55 µm 3.8 dB Crush test 490 N/10cm Fiber strength Connection effect 1.55 µm 20 %/min 1.55 µm 0.01 dB 5.2 GPa 36 dB Temperature depen dence of optical loss -30 1.55 µm
Page 1 and 2: ABSTRACT The configuration of optic
Page 3 and 4: cable should be able to be bent in
Page 5: Increasing the relative-index diffe
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