Recently, considerable research has been devoted to the development of optical components and devices that have the capability to support high-speed telecommunications. Silica base single-mode optical fiber has been widely utilized in the long distance trunk area for the order of giga bit per second transmission because of its high bandwidth and transparency. Introduction of the single-mode fiber into all trunk areas in Japan was completed in December 1997. Subsequently, the construction of fiber network in the access area which is called "π system" has started. In the π system, the single-mode optical fiber system is introduced to the curb, and the drop-line is operated by conventional metallic cables. Realization of all optical networks by single-mode fiber requires many breakthroughs in the total system cost. Because of the small core size (5 to 10 μm), accurate alignment is necessary in the light coupling to the fiber and the connection of fibers, which increases the total system cost including fiber connectors, transceiver, packaging, and installation, etc.
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