OPTICAL COMMUNICATION SYSTEM

PURPOSE:To easily execute the axial matching of an optical fiber, and also to raise the transmission characteristic, by varying in order the diameter of a core, the number of openings and the refractive index distribution factor of the optical fiber constituting an optical transmission line ranging a receiving terminal from a transmitting terminal. CONSTITUTION:An optical transmitter A having a light emission element and an optical receiver B having a photodetecting element are connected by an optical line L. The optical line L is formed by mutually connecting partitioned lines l1-l5. The diameter of a core, the number of openings and the refractive index distribution factor of each partitioned line are made minimum at the center line l3, and are made larger in order of its outside lines l2, l4 and subsequently l1, l5. In this way, as for the line whose core diameter is small and the line whose core diameter is large, the axial matching is executed easily, and the accuracy of a connector is alleviated. Furthermore, said line is connected with an optical fiber whose number of openings is large, with a small connection loss, the attenuation characteristic of an optical signal is improved by setting a refractive index distribution factor, and high optical power is secured.