Abstract: In order to couple an input end of an optical fiber to a light source designed to illuminate same with message signals, the light source--such as an LED--is mounted on a dielectric disk where it is surrounded by a flat ring confronting another ring with a stepped inner profile from which a cylindrical sleeve projects on the side opposite that disk. A capillary tube, closely fitting into the axial bore of the sleeve, is fitted around an extremity of the fiber stripped of its protective sheath so as to extend close to the source when the two rings are substantially coaxially juxtaposed; with the source energized, the light emitted at the opposite fiber end is measured to determine the correct alignment position in which the two rings are cemented to each other.

Abstract: In order to provide an end face of an optical fiber with a spherical curvature of predetermined radius, designed to optimize the transfer of luminous intensity from an adjoining light source such as a light-emitting diode, a flat fiber is heated to a temperature near its melting point while its profile is optically enlarged. When that profile is found to have reached a predetermined shape criterion, as determined by visual observation or by electronic scanning, heating is terminated.