The present invention provides novel apparatus and methods for fast quantitative measurement of perturbation of optical fields transmitted, reflected and/or scattered along a length of an optical fibre. The present invention can be used for point sensors as well as distributed sensors or the combination of both. In particular this technique can be applied to distributed sensors while extending dramatically the speed and sensitivity to allow the detection of acoustic perturbations anywhere along a length of an optical fibre while achieving fine spatial resolution. The present invention offers unique advantages in a broad range of acoustic sensing and imaging applications. Typical uses are for monitoring oil and gas wells such as for distributed flow metering and/or imaging, seismic imaging, monitoring long cables and pipelines, imaging within large vessel as well as for security applications.

The present invention provides novel apparatus and methods for fast quantitative measurement of perturbation of optical fields transmitted, reflected and/or scattered along a length of an optical fibre. The present invention can be used for point sensors as well as distributed sensors or the combination of both. In particular this technique can be applied to distributed sensors while extending dramatically the speed and sensitivity to allow the detection of acoustic perturbations anywhere along a length of an optical fibre while achieving fine spatial resolution. The present invention offers unique advantages in a broad range of acoustic sensing and imaging applications. Typical uses are for monitoring oil and gas wells such as for distributed flow metering and/or imaging, seismic imaging, monitoring long cables and pipelines, imaging within large vessel as well as for security applications.

A method of detecting a damage of a wind turbine blade of a wind turbine rotor includes: a light input step of inputting light into a fiber-optic sensor mounted to the wind turbine blade; a light detection step of detecting reflection light from the grating portion; an obtaining step of obtaining a wavelength fluctuation index representing a fluctuation amount of a wavelength of the reflection light detected in the light detection step; and a detection step. The detection step includes detecting the presence or the absence of the damage of the wind turbine blade based on the wavelength fluctuation index taking account of a correlation between the wavelength fluctuation index of the wind turbine blade and a load index related to a load applied to the wind turbine blade, or a correlation between the wavelength fluctuation index and a temperature index related to a temperature of the wind turbine blade.

A system configured to a plurality of zones of an aircraft includes first and second connectors are in optical communication, an optical fiber, a first interrogator, and a controller. The optical fiber extends between the first and second connectors and includes a first timing fiber Bragg grating disposed in the optical fiber at a reference location of the optical fiber. The first interrogator is connected to the optical fiber and is configured to provide a first optical signal to the optical fiber and to receive a first timing signal from the optical fiber. The first timing fiber Bragg grating is configured to provide the first timing signal with information related to the first timing fiber Bragg grating from the first interrogator. The controller is operatively connected to the first interrogator and is configured to determine the reference location of the optical fiber.

An optical fiber includes multiple optical cores configured in the fiber including a set of primary cores and an auxiliary core. An interferometric measurement system uses measurements from the multiple primary cores to predict a response from the auxiliary core. The predicted auxiliary core response is compared with the actual auxiliary core response to determine if they differ by more than a predetermined amount, in which case the measurements from the multiple primary cores may be deemed unreliable.

Embodiments of the present disclosure include a low crosstalk, optical fiber based disturbance detection system that includes single-mode optical fiber (SMF) arranged into dual ring Sagnac interferometer wherein both rings share a common sensing section of optical fiber path length. Certain embodiments further include fiber Bragg gratings (FBG's), circulators and couplers to be able to separate the optical signals of the two rings of the dual ring Sagnac interferometer and to perform processing of their individual signals. Embodiments are also disclosed that enable the position of a physical disturbance, the magnitude of the physical disturbance and the frequency of the physical disturbance to be known.

A long-distance optical cable physical safety monitoring system, including a light source module, a light interference module, a sensing module, a reflection module, a photovoltaic conversion module, and a data processing module. The light interference module is use for dividing a light beam into multiple light beams; the sensing module is use for transmitting the multiple light beams; the reflection module is used for reflecting the multiple light beams to make the light interference module to output an interference signal; the photovoltaic conversion module is used for converting the interference signal to obtain a data signal; the data processing module is used for processing the data signal. The long-distance optical cable physical safety monitoring system is passive, low in energy consumption, anti-jamming, low in false positive rate, simple in construction, and convenient in maintenance.

Optical polarization control devices that include two pairs of squeezing plates oriented in mutually perpendicular directions are described. Compressive forces exerted by the two pairs of plates onto an optical fiber can be configured for low polarization mode dispersion. Various methods and systems in which the polarization control devices can be employed are also described.

Embodiments of the present disclosure include a low crosstalk, optical fiber based disturbance detection system that includes single-mode optical fiber (SMF) arranged into dual ring Sagnac interferometer wherein both rings share a common sensing section of optical fiber path length. Certain embodiments further include fiber Bragg gratings (FBG's), circulators and couplers to be able to separate the optical signals of the two rings of the dual ring Sagnac interferometer and to perform processing of their individual signals. Embodiments are also disclosed that enable the position of a physical disturbance, the magnitude of the physical disturbance and the frequency of the physical disturbance to be known.

An optical fiber includes multiple optical cores configured in the fiber including a set of primary cores and an auxiliary core. An interferometric measurement system uses measurements from the multiple primary cores to predict a response from the auxiliary core. The predicted auxiliary core response is compared with the actual auxiliary core response to determine if they differ by more than a predetermined amount, in which case the measurements from the multiple primary cores may be deemed unreliable.