In an optical signal transmission system which can perform high-speed optical transmission not lower than 1 Gbps (9), a VCSEL has several light-emission points. A core diameter of the optical fiber (GI-POF) is set to not lower than 200 mu m, and the light-emission points graded index polymer of the VCSEL are arranged inside an outer periphery of the core at an end face of the GI-POF. A polymerization composition material constituting the core of the GI-POF is made of a compound containing deuterated poly methacrylic ester. A wavelength of the light beam of the VCSEL is set to the range of 770 nm to 810 nm.