Abstract: Reflectometric vibration measurement system to monitor multiphase flows in production wells or pipelines using multimode fibers comprising: —a sensing multimode optical fiber; —an optical source with at least one fiber output port, which generates optical pulses which are to be sent to the sensing fiber; —an optical receiver with at least one multimode fiber input port; —an optical device with at least 3 multimode fiber ports, in which one port is connected to the optical source, one port to the optical receiver, and one port to the sensing multimode fiber; —a system for processing the output signals from the optical receiver, further comprising more than one spatial mode filter. A process for reconfiguring an optical reflectometry system which has already been installed in a monitoring structure is also described.

Abstract: A vibration measurement system and relative method to monitor multiphase flows in extraction wells or conduits, by analysis of backscattered multimode fiber light comprising: • a sensing multimode optical fiber; • an optical source, containing a high coherence laser that emits optical pulses to be sent in said sensing fiber; • a photonic lantern with 3 or more single-mode optical fiber ports and one multimode fiber port that is connected to the sensing multimode fiber; • an optical receiver, comprising a number of photodetectors equal to the number of the single-mode optical fiber ports of said photonic lantern minus 1, wherein each photodetector is connected to each of said single-mode ports; • a system for processing output signals from the optical receiver, the optical source being connected to one of the single-mode optical fiber ports and the other single-mode fibers being connected to the optical receiver.

Abstract: A method for detecting an electrical current longitudinal variation in a power transmission system including a power cable. Electric losses and their location along the cable length can be detected. Current variation in a grounded metallic layer of a power cable is measured from Faraday rotation of polarised light travelling in a single-mode optical fiber wound in a radially external position with respect to the grounded metallic layer. Measurements of the Faraday rotation are carried out by means of polarization-sensitive optical time domain reflectometry (POTDR) or by polarization-sensitive optical frequency domain reflectometry (POFDR) while a direct current is injected in the metallic layer.

Abstract: Reflectometric vibration measurement system to monitor multiphase flows in production wells or pipelines using multimode fibers comprising: a sensing multimode optical fiber; an optical source with at least one fiber output port, which generates optical pulses which are to be sent to the sensing fiber; an optical receiver with at least one multimode fiber input port; an optical device with at least 3 multimode fiber ports, in which one port is connected to the optical source, one port to the optical receiver, and one port to the sensing multimode fiber; a system for processing the output signals from the optical receiver, further comprising more than one spatial mode filter. A process for reconfiguring an optical reflectometry system which has already been installed in a monitoring structure is also described.

Abstract: A vibration measurement system and relative method to monitor multiphase flows in extraction wells or conduits, by analysis of backscattered multimode fiber light comprising: • a sensing multimode optical fiber; • an optical source, containing a high coherence laser that emits optical pulses to be sent in said sensing fiber; • a photonic lantern with 3 or more single-mode optical fiber ports and one multimode fiber port that is connected to the sensing multimode fiber; • an optical receiver, comprising a number of photodetectors equal to the number of the single-mode optical fiber ports of said photonic lantern minus 1, wherein each photodetector is connected to each of said single-mode ports; • a system for processing output signals from the optical receiver, the optical source being connected to one of the single-mode optical fiber ports and the other single-mode fibers being connected to the optical receiver.

Abstract: A method for detecting an electrical current longitudinal variation in a power transmission system including a power cable. Electric losses and their location along the cable length can be detected. Current variation in a grounded metallic layer of a power cable is measured from Faraday rotation of polarised light travelling in a single-mode optical fibre wound in a radially external position with respect to the grounded metallic layer. Measurements of the Faraday rotation are carried out by means of polarization-sensitive optical time domain reflectometry (POTDR) or by polarization-sensitive optical frequency domain reflectometry (POFDR) while a direct current is injected in the metallic layer.

Abstract: A method for monitoring a torsional state of a cable having a central longitudinal axis, includes providing a cable including a torsion sensor longitudinally extending along the cable, the torsion sensor including a single-mode optical fiber arranged substantially along the central longitudinal axis of the cable, and at least three longitudinal structural elements, at least one of the longitudinal structural elements being an electrically conductive core, wherein the torsion sensor is mechanically coupled with at least one of the longitudinal structural elements; measuring a torsional state of the single-mode optical fiber by polarization-sensitive optical reflectometry; and associating the torsional state of the cable along the longitudinal axis with the measured torsional state of the single-mode optical fiber.

Abstract: An oil-hydraulic system for moving a gate, comprises a double-acting oil-hydraulic cylinder (11), which is intended to be kinematically connected to the gate to move it, and an electro-hydraulic pump (12) to feed and actuate the cylinder upon command. A switching valve (13) interconnects the cylinder (11) alternatively with the pump (12) or with a tank (14) of oil-hydraulic fluid. In rest conditions, the valve (13) connects the cylinder (11) to the tank (14), to allow free manual movement of a gate connected to the cylinder, and it is automatically controlled by the pressure variations in the system that are produced by the actuation of the pump (12) to disconnect the cylinder (11) from the tank (14) and connect it to the pump (12).

Abstract: A method for monitoring a torsional state of a cable having a central longitudinal axis, includes providing a cable including a torsion sensor longitudinally extending along the cable, the torsion sensor including a single-mode optical fiber arranged substantially along the central longitudinal axis of the cable, and at least three longitudinal structural elements, at least one of the longitudinal structural elements being an electrically conductive core, wherein the torsion sensor is mechanically coupled with at least one of the longitudinal structural elements; measuring a torsional state of the single-mode optical fiber by polarisation-sensitive optical reflectometry; and associating the torsional state of the cable along the longitudinal axis with the measured torsional state of the single-mode optical fiber.

Abstract: An oil-hydraulic system for moving a gate, comprises a double-acting oil-hydraulic cylinder (11), which is intended to be kinematically connected to the gate to move it, and an electro-hydraulic pump (12) to feed and actuate the cylinder upon command. A switching valve (13) interconnects the cylinder (11) alternatively with the pump (12) or with a tank (14) of oil-hydraulic fluid. In rest conditions, the valve (13) connects the cylinder (11) to the tank (14), to allow free manual movement of a gate connected to the cylinder, and it is automatically controlled by the pressure variations in the system that are produced by the actuation of the pump (12) to disconnect the cylinder (11) from the tank (14) and connect it to the pump (12).

Abstract: A method of determining characteristic spin parameters of a spun optical fiber by performing optical time-domain reflectometry measurements on the fiber, so as to obtain a state of polarization spatial function from a backscattered electromagnetic field, the state of polarization spatial function being defined by a plurality of components; and processing the state of polarization spatial function. The process includes calculating a further spatial function related to the spatial first derivative of at least one of the components of the state of polarization spatial function; identifying a spatial periodicity of the further spatial function; and determining the characteristic spin parameters as a function of the spatial periodicity.

Abstract: A method of determining characteristic spin parameters of a spun optical fiber by performing optical time-domain reflectometry measurements on the fiber, so as to obtain a state of polarization spatial function from a backscattered electromagnetic field, the state of polarization spatial function being defined by a plurality of components; and processing the state of polarization spatial function. The process includes calculating a further spatial function related to the spatial first derivative of at least one of the components of the state of polarization spatial function; identifying a spatial periodicity of the further spatial function; and determining the characteristic spin parameters as a function of the spatial periodicity.

Abstract: An apparatus for compensation or emulation of polarization mode dispersion (PMD) effects occurring in an optical signal traveling over an optical fiber based link comprises controllable birefringence sections and devices for polarization conversion. Each section comprises birefringence optical members or parts thereof, and each section is followed or preceded by one of the controllable devices for polarization conversion. The birefringence sections are at least three in number, and at least one of these has a propagation delay different from that of the other sections. The apparatus comprises a detection device for PMD output and control of the controllable devices for feedback adjustment.

Abstract: A method of detecting polarization mode dispersion (PMD) indicative parameters of an optical fiber link comprising at least one transmission channel in which is transmitted a first wideband optical signal with a bandwidth divided into sub-bands. For each sub-band is produced a second reference optical signal with which to find a third optical signal by superposition. For each of the third signals are calculated first parameters considered indicative of the PMD thereof, and with the first parameters of all the sub-bands are calculated second parameters considered indicative of the PMD of the first wideband signal. The method can be used as part of a PMD compensation method for a transmission system employing the parameters calculated for feedback piloting of a PMD compensator.

Abstract: A method for determining at least one parameter of a periodic spin function ?(z) with period p, to be applied to an optical fiber along its length z during a drawing process. At least one parameter is selected so that (I) where ?1 is about 0.05 and y1 is the first of the three components y1(z), y2(z), y3(z) of a periodic function y(z) of period p such that (II) where LB is an expected beat length of said optical fiber and ?(z) is the derivative of the spin function ?(z) with respect to the length z. The method is effective for substantially reducing the PMD of optical fibers drawn when applying a spin function.

Abstract: An apparatus (14) for compensation or emulation of PMD effects occurring in an optical signal travelling over an optical fiber based link comprises controllable birefringence sections (15-18) and devices (19-22) for polarization conversion. Each section comprises birefringence optical members or parts thereof and each section is followed or preceded by one of said controllable devices for polarization conversion. The birefringence sections (15-18) are at least three in number and at least one of these has a propagation delay different from that of the other sections.

Abstract: The process and apparatus to enable measurement of polarization dispersion of a single-mode optical fibre by launching measurement light at one end of the fibre and analyzing polarization of the light reflected by the other end and collected at such launch end. Optical or electronic masking of light reflected by the near end of the fibre is performed during launch.

Abstract: A method for determining at least one parameter of a periodic spin function &agr;(z) with period p, to be applied to an optical fibre along its length z during a drawing process. At least one parameter is selected so that (I) where &egr;1 is about 0.05 and y1 is the first of the three components y1(z), Y2(z), y3(z) of a periodic function y(z) of period p such that (II) where LB is an expected beat length of said optical fibre and &agr;(z) is the derivative of the spin function &agr;(z) with respect to the length z. The method is effective for substantially reducing the PMD of optical fibres drawn when applying a spin function.