PURPOSE: To connect glass fibers of poor water resistance and chemical resistance so as to permit transmission with less losses by incorporating the constitution comprising dividing a core to two parts in the connector having the core for holding glass fibers and a cylindrical body containing this.

CONSTITUTION: A quartz-base glass fiber 13 of good water resistance is inserted and fixed in the form of being removed of the resin clad part in the first core 12 in a tubular body 11. A glass fiber 15 of slightly inferior water resistance is inserted and fixed in the state of being removed of its resin clad part 16 in the second core 14. Silicon resins are coated on the end face D where the first core 12 and second core 14 contact and the end face C of the glass fiber 15. The tubular body 11 and the outside circumferential surface of the second core 14 are secured by means of an instant-set adhesive H. Such constitution obviates receiving the effect of the moisture in air even if the connection part exposes to the air because the end faces are formed of quartz glass of good water resistance.