The present disclosure relates to a passive fiber optic cabinet and a system for detecting a state of a door of a passive fiber optic cabinet. A passive fiber optic cabinet is provided, comprising: a housing; a door coupled to the housing and configured to be switchable between an open state and a closed state; a switch sensor module including a detection fiber Bragg grating (FBG) sensor and a stress applying mechanism corresponding to the detection FBG sensor, the stress applying mechanism configured to apply a stress o the detection FBG sensor, one of the detection FBG sensor and the stress applying mechanism being positioned at the door, and the other of the detection FBG sensor and the stress applying mechanism being positioned at the housing.

A system for interrogating sensors in a fiber optical sensor network includes groups of sensors. The sensors in one group operate at different wavelengths, and the sensors of other groups may have overlapping wavelengths. A light source generates a broadband light signal, input and output means for guides the broadband light to the fiber optical sensor network for illuminating the sensors and for coupling the light signal coming from the sensors of the fiber optical sensor network to the detection system, and a detection system detects the received light signal, during a detection integration time. The system is arranged for selecting pre-dominantly the received light coming from the different sensors of a selected group of sensors using a code-division multiplexing technique and simultaneously detecting sensors of the selected group of sensors using a wavelength-division multiplexing technique.

The present invention relates to an apparatus for optical applications, a spectrometer system and method for producing an apparatus for optical applications, and in particular to an apparatus comprising an optical waveguide having a first refractive index along a light propagation axis interrupted by a plurality of scattering portions having a second refractive index. Each scattering portion has a long axis substantially perpendicular to the light propagation axis as well as a short axis substantially perpendicular to the light propagation axis and the long axis. A receiver unit or a transmitter unit is arranged on a side of the optical waveguide, the long axis being substantially perpendicular, i.e. normal to the plane of this side on which the receiver unit or transmitter unit is arranged. Accordingly, simplification and miniaturization of an optical apparatus can be realized.

A method of determining perturbation of a grating formed in an optical fiber, comprises: modulating and transmitting a light beam through the optical fiber, measuring at least one phase shift in a modulation of light reflected off the grating, and determining the perturbation of the grating based on the phase shift(s).

Temperature measurements of photonic circuit components may be performed optically, exploiting a temperature-dependent spectral property of the photonic device to be monitored itself, or of a separate optical temperature sensor placed in its vicinity. By facilitating measurements of the temperature of the individual photonic devices rather than merely the photonic circuit at large, such optical temperature measurements can provide more accurate temperature information and help improve thermal design.

An erosion sensor includes one or more optical fibres each having one or more cores and an optical sheath surrounding the one or more cores, a variable pitch measurement Bragg grating inscribed in one of the cores of one of the optical fibres over a measurement section to be eroded, and one or more reference Bragg gratings each inscribed in one of the cores. The reference Bragg grating is used to correct the physical length of the measurement section determined from the width of the spectrum reflected by the measurement Bragg grating, taking into account the thermomechanical parameters imposed on the erosion sensor.

The present disclosure discloses an optical element for measuring a change in strain. The optical element has ends and first and second portions for guiding light which extend between the ends of the optical element and are mechanically coupled to each other at at least one position. Each of the first and second portions for guiding light comprise at least one Bragg grating. The optical element is arranged such that, when an axial or uniaxial strain is equally applied to the first and second portions for guiding light at the ends of the optical element, an optical response from the at least one Bragg grating of the first portion for guiding light differs from an optical response form the at least one Bragg grating of the second portion for guiding light.

An apparatus for locating a measurand anomaly, such as a hot-spot, along an optical waveguide is provided comprising: an optical waveguide, a light source configured to transmit pulsed light along the waveguide, and a first and second set of sensors provided along the waveguide. Each sensor is configured to reflect a portion of light propagating along the waveguide at a respective sensor wavelength corresponding to a measurand. The first set of sensors provides one or more groups of sensors configured to detect a measurand anomaly within that group. The second set comprises a plurality of sensors each separated from the adjacent sensor of that set by a distance along the waveguide greater than half the distance travelled by the light along the waveguide during the pulse duration. A plurality of sensors of the first set is provided between each adjacent sensor of the second set. The apparatus further comprises a detector configured to monitor the light reflected by the sensors, and a control system configured to control the light source and the detector to both locate at least the group containing a measurand anomaly and to monitor the measurand using the second set.

An apparatus, and related method, relates generally to a fiber-optic sensing system. In such a system, fiber-optic sensors are in a rosette or rosette-like pattern. An optical circulator is coupled to receive a light signal from a broadband light source, to provide the light signal to the fiber-optic sensors, and to receive a returned optical signal from the fiber-optic sensors. A spectral engine is coupled to the optical circulator to receive the returned optical signal and configured to provide an output signal.

An optical sensing system comprising an optical fiber, a light source, a first interrogator and a second interrogator. The optical fiber includes one or more optical sensors. The light source is placed at a first end of the optical fiber and is configured to direct light towards the one or more optical sensors. The first interrogator is placed at the first end of the optical fiber. The second interrogator placed at a second, opposite end of the optical fiber. The first interrogator is configured to receive reflected light from the one or more optical sensors, and the second interrogator is configured to receive transmitted light from the one or more optical sensors.