Fibre linear cavity ring down device for decay time-based attenuation sensing, comprising a bi-directional fibre optic coupler having two fibre port coupling sides, a left-hand port side and a right-hand port side, and a port mirror; wherein signal input on one of said sides is coupled to signal output on the other of said sides; wherein the left-hand port side comprises a first fibre port (port 1) for coupling to an optical light source, the left-hand port side comprises a second fibre port (port 2) coupled to said port mirror (mirror 2), and the right-hand port side comprises a third fibre port (port 3) for coupling to a sensor fibre comprising one or more sensors and optically terminated by a sensor fibre mirror (mirror 1). The optical light source may be also an optical light receiver. The optical light source and receiver may preferably be an optical time domain reflectometer.

In a sensor device, a plurality of light guides having a respective first end and a respective second end are arranged on a common carrier, with the first end of each light guide of the plurality of light guides at a respective defined position on the carrier. At each of the second ends of the light guides there is provided at least one sensor element which exhibits an optical behavior dependent on an analyte. The second ends are at defined perpendicular distances to the carrier. At least two of the second ends differ with respect to the defined perpendicular distances.

A gas detection apparatus (100) includes a first layer (1) and a second layer (2) disposed opposite the first layer (1) in a predetermined direction (z-axis direction). The first layer (1) includes a light emitter that emits light and a light receiver that receives the light after the light passes through a waveguide. The second layer (2) includes a light input unit of the waveguide opposite the light emitter in the predetermined direction (z-axis direction) and a light output unit of the waveguide opposite the light receiver in the predetermined direction (z-axis direction). The gas detection apparatus (100) can be miniaturized.

Plasmonic optical fibers, plasmonic optical sensors and methods of manufacturing the same. A fiber core conveys an optical signal therewithin and provides a plasmonic sensing area exposed to a fluid. The plasmonic sensing area is formed only on a section of an external surface of the fiber core. The plasmonic sensing area provides an interface within the section of the external surface for the conveyed signal to at least partially exit the fiber core and cause a modified optical signal to be conveyed in the fiber core. An optical signal generator may provide the optical signal to the plasmonic optical fiber, an optical signal receiver may discriminate the conveyed optical signal from the modified optical signal and a processor module may analyze the modified optical signal and identifies physical characteristics of the fluid present at the sensing area.

Disclosed is an optical fiber including a plasmonic optical filter with a closed curved shape provided at, at least portion thereof. A method of manufacturing the plasmonic optical filter includes a step of exposing a core, a step of forming a thin metal film on the core through physical vapor deposition while rotating the core in a circumferential direction after changing a rotation axis of the core, and a step of patterning nanopatterns on the cylinder-shaped thin metal film using focused ion beam technique assisted with endpoint detection method. Due to such constitutions, an active area to generate an optical signal for optical sensor can be increased.

An infrared (IR) sensor and a method of detecting molecular species in a liquid. In one embodiment, the method comprises i) generating IR light from an IR light source; ii) receiving in an optical fiber the IR light from the IR light source, wherein a selective ion-exchange (IX) medium is associated with the optical fiber and the IR light generates an evanescent field about the optical fiber as the IR light propagates therethrough, the selective IX medium configured to transport an ion species in a subject liquid about the optical fiber; and iii) receiving in an IR light detector the IR light from the optical fiber, wherein the ion species affects the evanescent field and thereby a characteristic of the IR light.

A system and method for detecting and determining the location of (i) defects in railroad track rails and (ii) the presence of cars, trains or vehicles on the rails. A strain sensitive fiber optic cable is continuously bonded to each section of rail, with the cables of adjacent rails being interconnected by non-strain-sensitive fiber optic cable. A detection system provides an optical backscatter sensing function and an optical time domain reflectometry analysis and distance determining function to determine the nature and location of rail anomalies and vehicle presence on the rails.

The present invention relates to a method for detecting the presence of gas hydrates and/or ice in a medium. The method comprises at least the following steps:

measuring at least at one measurement point in said medium two characteristic values of Raman spectra corresponding to two distinct vibration modes of the OH bonds of water, and determining the ratio of said two characteristic values,

determining the temperature T in said medium at said measurement point of said spectra,

comparing ratio with a value T.sub.0 corresponding to a predetermined threshold of formation of said crystals for said temperature T, and

determining the presence or not of hydrate and/or ice crystals from said comparison.

A novel system and method for detecting a quench of a superconducting conductor and detecting abnormal behavior of a superconducting conductor using acoustic sensor technology in the coolant of a superconducting cable and/or magnet is disclosed. This system and method is not only limited to use for superconductors, but also may be used for any device disposed in liquid and gas. Acoustic sensors are installed along a coolant space of a superconducting conductor and monitor coolant conditions. By monitoring acoustic changes, temperature changes or coolant flow disruption can be detected very quickly by an acoustic sensor array. By disposition of the acoustic sensor array in a coolant flow channel, the acoustic sensor system can quickly detect a local condition, such as the thermal status (temperature) of a superconducting cable and magnet with precise spatial resolution.

An infrared (IR) sensor and a method of detecting molecular species in a liquid. In one embodiment, the method comprises i) generating IR light from an IR light source; ii) receiving in an optical fiber the IR light from the IR light source, wherein a selective ion-exchange (IX) medium is associated with the optical fiber and the IR light generates an evanescent field about the optical fiber as the IR light propagates therethrough, the selective IX medium configured to transport an ion species in a subject liquid about the optical fiber; and iii) receiving in an IR light detector the IR light from the optical fiber, wherein the ion species affects the evanescent field and thereby a characteristic of the IR light.