Group of optic sensors (S) in a weft feeder, in particular for weaving looms, comprising one or more pairs of emitting sensors (E) and receiving sensors (R) arranged on a portion of the weft feeder (C) which extends laterally to the drum (T) of the weft feeder whereon the coils of the weft thread are wound, so as to form optic radiation going-paths from each of said emitting sensors (E) to a reflecting surface (9) provided on said drum (T) and optic radiation back-paths, from said reflecting surface (9) to corresponding receiving sensors (R), for detecting the presence/absence of a thread which crosses said paths. The optic sensors (E, R) are of the SMT type and are wired on a printed-circuit board (8) with an optic axis parallel to the plane of said board (8). A first group of total-reflection mirrors (V), one for each pair of emitting/receiving sensors (E, R), is inclined so as to deviate the optic radiation from the plane of the board (8) to a plane perpendicular to or inclined with respect to the same. A second group of partial-reflection mirrors (H), one for each pair of emitting/receiving sensors (E, R), is inclined so as to deviate the optic radiation in the same plane as board 8.
