Abstract: A device is provided for generating, from a single light pulse of brief duration, a train of synchronous light pulses each comprising at most one photon on average, comprising several optical paths (1.sub.1, 1.sub.2, . . . 1.sub.n) each formed by at least one single mode optical fiber with zero dispersion in the form of a loop closed on itself by end to end connection of its ends by at least one connector (20); the number of loops is n if the number N of the photons in the initial pulse is greater than 10.sup.2n ; these loops are joined together two by two, following each other, by first directional optical coupling means (2.sub.12, 2.sub.23, . . . 2.sub.(n-1)n) having a relatively small optical coupling coefficient equal to about (1/N).sup.1/(n+1) ; second directional optical coupling means (3.sub.1, 3.sub.n) also having a relatively low optical coupling coefficient joining the first (1.sub.1)and last (1.sub.