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: 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: 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: 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: 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.

Abstract: The present invention aims to provide apparatus to measure the beat length, the correlation length, the polarization mode dispersion and other characteristics of single mode optical fibers related to the two polarization modes of the fiber at different positions along the length of the fiber. The present invention also aims to provide apparatus for the measurement of characteristics of an optical fiber with access to only one end of the fiber.