Prysmian S.p.a.

Antonio Faraldi

Franco Cocchini

Antonio Adigrat

Antonio Collaro

Francesco Di Matteo

Paolo Russo

Gerardo Testa

A method for inspecting defects inside a rod-shaped transparent object by using a scanning beam of parallel light rays directed onto a rod-shaped transparent object orthogonally to the longitudinal axis of the object so that an inspection plane comprises an object's cross-section. The scanning beam is detected at an opposite side of the rod-shaped object that is interposed to intercept the parallel rays of the scanning beam. The electric output signal from the detector is processed to produce a first light intensity profile in a first scan direction, the light intensity profile comprising a shadow region delimited by first and second shadow edges, which is indicative of the outside diameter of the object across the inspection plane. The method comprises analyzing the first light intensity profile to determine the presence or absence of a peak of positive intensity within the shadow region and, if an intensity peak is determined to be present, to determine the presence or absence of a region of depressed intensity within the intensity peak. If, as a result of analyzing, an intensity peak within the shadow region is determined to be absent or a region of depressed intensity is determined to be present within the intensity peak, the presence of at least one structural defect within the object's cross-section is identified. In the preferred embodiments, the rod-shaped transparent object is a glass core rod for the production of a transmission optical fiber.

Method for detecting defects in a rod-shaped transparent object

A manufacturing process of a microstructured optical fiber including a void-containing region, includes the steps of: drawing a microstructured optical fiber along a longitudinal direction from a heated preform, wherein the optical fiber is continuously advanced along the longitudinal direction; directing a radiation beam at a longitudinal position in the longitudinal direction of the optical fiber so as to produce an interference pattern; detecting the interference pattern and producing at least one electrical detection signal corresponding to the interference pattern and including a plurality of signal fringe cycles; feeding the first detection signal into a first counter circuit; determining a first number of interference fringe increments in the plurality of signal wave fringe cycles of the at least one detection signal by using the first counter circuit; determining the outer diameter of the optical fiber, and controlling the microstructure of the optical fiber during advancement of the optical fiber. The step of controlling includes at least one step selected from: (a) controlling the first number of interference fringe increments within a reference number range of reference numbers of interference fringe increments, and (b) calculating a microstructure length value.

Process for manufacturing a microstructured optical fibre and method and system for on-line control of a microstructured optical fibre

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Milan, Italy

Antonio Faraldi