PURPOSE: To provide a production method for optical fiber coupler which determines the characteristic by the tension given at the time of fixing an optical fiber coupler to a reinforcing member.

CONSTITUTION: When a tension is given to the optical fiber coupler already subjected to welding and stretching, the characteristic is different by the strength of this tension. The figure shows a modeled emission power/tension curve in one emission port. In an area B1, the emission power is monotonously increased according as the tension is increased. An area A is a maximum area. In an area B2, the emission power is monotonously decreased according as the tension is increased. An area C is the convergence area where the emission power is less varied by the change of the tension. Consequently, the tension corresponding to a desired characteristic is given and the optical fiber coupler is fixed to the reinforcing member in this state.