A method of fabricating an opto-pyrotechnic initiator, includes a) forming a body having a cavity in which a pyrotechnic charge is to be received, the body also having an internal passage extending between the cavity containing the pyrotechnic charge and an inlet opening out in an outside face of the body; b) placing a first portion of an optical fiber in the internal passage of the body, with a second portion of the optical fiber extending beyond the inlet of the body, and a glass preform being interposed between the optical fiber and the inlet of the body; and c) applying heat treatment to the glass preform to raise the glass preform to a temperature higher than the melting point of the glass preform so as to form a hermetic sealing element made of glass between the optical fiber and the inlet of the body.