Abstract: The present invention discloses practical and power efficient assemblies for applying a temperature gradient to a fiber Bragg grating. An application of such assemblies is, for example, the active tuning of the chromatic dispersion of the grating. The temperature gradient is produced in a heat conductive element, with which the FBG is in continuous thermal contact, by elements controlling the temperature of the ends of the heat conductive element, thereby applying the temperature gradient to the FBG. A first preferred embodiment includes a heat recirculation member allowing the recirculation of heat between the two ends of the heat conductive elongated element, thereby providing a rapid and dynamical tuning of the temperature gradient with a minimal heat loss. A second embodiment provides isolation from the surrounding environment in order to decouple the desired temperature gradient from ambient temperature fluctuations, thereby improving the control of the optical response of a fiber grating.

Abstract: The present invention discloses practical and power efficient assemblies for applying a temperature gradient to a fiber Bragg grating. An application of such assemblies is, for example, the active tuning of the chromatic dispersion of the grating. The temperature gradient is produced in a heat conductive element, with which the FBG is in continuous thermal contact, by elements controlling the temperature of the ends of the heat conductive element, thereby applying the temperature gradient to the FBG. A first preferred embodiment includes a heat recirculation member allowing the recirculation of heat between the two ends of the heat conductive elongated element, thereby providing a rapid and dynamical tuning of the temperature gradient with a minimal heat loss. A second embodiment provides isolation from the surrounding environment in order to decouple the desired temperature gradient from ambient temperature fluctuations, thereby improving the control of the optical response of a fiber grating.

Abstract: Arrangement for the ultrasonic examination of objects by a local immersion technique, comprising:a source of liquid,a pump fed by said source,a coupling head fed with liquid by said pump and capable of directing towards the object to be examined a jet of the said liquid and a beam of ultrasonic waves which is contained in said jet and is coaxial with this jet, said coupling head comprising:(a) a first tranquilization chamber connected to the outlet of said pump,(b) a second cylindrical tranquilization chamber connected to the said first chamber by at least one channel for the passage of the liquid,(c) an ultrasonic transducer capable of emitting a beam of ultrasonic waves by means of an active surface, which is directed towards the object, said active surface being situated in the second chamber, centered on the axis of said second chamber and perpendicular to this axis,(d) a converging system coaxial with the said second chamber, the shape of which results from a calculation for the purpose of reducing or el