| 摘要 |
PROBLEM TO BE SOLVED: To realize an optical transmission at a high speed by a simple optical system while maintaining a high coupling efficiency as it is. SOLUTION: By using a LED, made of InP, easy to modulate at high speed and having a central light emitting wavelength of 1.31μm for a semiconductor light emitting element as a photo-electric converter, a plastic clad fiber(PCF) 24 whose angle of light receiving visual field is large, about 0.4, being currently in practical use and an optical system whose numerical aperture on the side of PCF 24 is <=0.3 for a coupling optical system, a high-speed modulated signal having a transmission velocity >=100Mbps is transferred longer than 1km under the condition that light emerged from the LED 21 is efficiently coupled to PCF 24. Consequently, in an intermediate distance region in which a communication distance is about 1km, since an optical system with a large price structure ratio is made inexpensive, an inexpensive system is constituted without lowering the transmission speed.
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