Organisation Europeenne Pour La Recherche Nucleaire

Claude Bovet

Edward M Rossa

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.n) loops with external optical paths (respectively 4 or 7; 5 or 8) respectively for the input of only a small part of the initial light pulse and for the output of the train of equidistant pulses formed at most of a single photon on average; the periods of rotation of the photons in the loops are equal to integral numbers, prime with respect to each other, of elementary periods T; and the periods of rotation of the photons in the loops are sufficently small so that the photons remaining in the loops at the end of a sampling procedure do not form a background noise troublesome for the following sampling procedure.

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Founex, Switzerland

Claude Bovet