Abstract: Sensors suitable for submarine detection are in the form of multilayer polymer beads. The sensors have a change in detectible property, such as color, which occurs when said sensors are exposed to a particular stimulus such as an object or event to be detected. The change in property is thus detectible by an external monitor.

Abstract: A system for the measurement and surface data acquisition for optical fiber sensors containing Bragg gratings for the sensing of physical parameters originated from a set of oil wells, the system including: an optical system for signal processing, the signals being originated from physical parameters sensors installed in one single or in a set of oil and/or gas wells and resulting from the reflected wavelength in response to a perturbation of the physical parameter under measurement; an electronic system for signal processing for converting the optical intensity signals originated from the optical system into electrical signals with the aid of detectors that optimize the signal/noise ratio; and an optical switcher having an interface between a) and b), for expanding the number of monitored oil wells.

Abstract: The present invention discloses a fiber Bragg grating sensor system.

Abstract: A main line cable and a backup line cable are laid in a land portion in different routes. A land terminal station includes a break detecting unit that detects a break of the main line cable, and a path switching unit that switches a transmission path to the backup line cable. The break detecting unit detects a break of the cables based on a received-light level of a main signal transmitted from an underwater cable, or based on a received-light level of a returned monitor signal that has been output by the break detecting unit and reflected by the beach manhole. The beach manhole includes optical couplers that couple and divide the main signal for the main line cable and the backup line cable, a fiber grating that reflects the monitor signal, and an optical director.

Abstract: A wear determination device for determining vibration in a turbine engine component to reduce wear in a turbine engine. The wear determination device may be capable of measuring vibrations in a turbine engine component. The vibration measurement may be used to determine vibrations in a turbine engine to identify wear locations and sources of wear. The wear determination device may be configured such that multiple locations in a turbine engine may be monitored on a single turbine engine by moving the wear determination device from location to location.

Abstract: A device comprising a fiber grating loop ringdown (FGLRD) system of analysis is disclosed. A fiber Bragg grating (FBG) or Long-Period grating (LPG) written in a section of single mode fused silica fiber is incorporated into a fiber loop. By utilizing the wing areas of the gratings' bandwidth as a wavelength dependent attenuator of the light transmission, a fiber grating loop ringdown concept is formed. One aspect of the present invention is temperature sensing, which has been demonstrated using the disclosed device. Temperature measurements in the areas of accuracy, stability, high temperature, and dynamic range are also described.

Abstract: An optical displacement transducer includes a transducing element comprising at least a first optical fiber, having a first end face substantially aligned along an axis and positioned with a small gap between said first end face and a second end face of a reception assembly, the transducer further comprising at least a light source coupled for transmission to first optical fiber and at least a photo-detector coupled for reception to the second optical fiber. The first end face and the second end face are displaceable along the axis and relatively with respect to each other, in order to follow the displacement of points associated to the first end face and second end face. The transducer is effective in detecting axial displacement simply and low cost.

Abstract: Light to be sensed is spreaded across an entry surface of a transmission structure with a laterally varying energy transmission function. For example, the light could be output from a stimulus-wavelength converter, provided through an optical fiber, or it could come from a point-like source or broad area source. Output photons from the transmission structure can be photosensed by photosensing components such as an array, position sensor, or array of position sensors. Wavelength information from the light can be obtained in response to the photosensing component. Spreading can be performed by air, gas, transparent material, or vacuum in a gap, by a region or other part of a lens, or by an optical fiber end surface. If the light comes from more than one source, a propagation component can both spread the light and also keep light from the sources separate.

Abstract: The present invention relates to optical confinements, methods of preparing and methods of using them for analyzing molecules and/or monitoring chemical reactions. The apparatus and methods embodied in the present invention are particularly useful for high-throughput and low-cost single-molecular analysis.

Abstract: The present invention relates to a determination of a physical state of an optical device by measuring a response signal. At least two subsequent measurements are executed. Therefore, a first optical signal is transmitted to the optical device, wherein a first optical property of said first signal is varied according to a first function of the time. A second optical property of a first response signal returning from the optical device is measured over the time and a first result function of the second optical property of the first response signal over the first optical property of first optical signal is established. Further, a second optical signal is transmitted to the optical device, wherein the first optical property of said signal is varied according to a second function of the time that is different from the first function of time.

Abstract: The present invention relates to optical confinements, methods of preparing and methods of using them for analyzing molecules and/or monitoring chemical reactions. The apparatus and methods embodied in the present invention are particularly useful for high-throughout and low-cost single-molecular analysis.

Abstract: A method and apparatus for optically clocked optoelectronic track and hold (“OCOETH”) device. The OCOETH device includes a diode bridge, input node, at least two current sources and at least two photodetectors. The input node is operatively coupled to the diode bridge and can receive an analog input signal. The at least two current sources are operatively coupled to the diode bridge and can forward bias the diode bridge. The at least two photodetectors are operatively coupled to the diode bridge and can receive an optical input clocking signal, and can reverse bias and forward bias the diode bridge in response to the optical input clocking signal. The hold capacitor is operatively coupled to the diode bridge and can track the analog input signal when the diode bridge is forward biased, and can hold the analog input signal when the diode bridge switches from forward biased to reverse biased.

Abstract: An apparatus is provided to effectively reduce the non-active detection gap between sensor elements of an optical sensor. Reducing the non-active gap can subsequently reduce the time delay between sensor elements, mitigating the image degrading effects of a composite element time delay. While applicable to use with a wide range of optical sensors, the invention may be used for detecting aspects of a variable-rate dynamic colorful object using a matrix sensor or a tri-linear color CCD sensor. In one variation, optical fibers extend from a first fiber optic faceplate to a second fiber optic faceplate. The optical fibers can be oriented toward or directly mounted to the sensor elements. A spacer may be used to separate the optical fibers for alignment with the sensor elements and the other end of the optical fibers are attached to each other.

Abstract: A mechanism for mapping an anatomical characteristic of a patient includes a treatment bed having a top surface. A fiber Bragg grating channel is disposed along at least a portion of the treatment bed near the top surface and includes a fiber optic waveguide defining a plurality of spaced-apart Bragg-type gratings. A multi-wavelength light source generates a beam that is in optical communication with the fiber Bragg grating channel. A detector, in optical communication with the fiber Bragg grating channel, detects reflections of light from at least one of the Bragg-type gratings. A computer is programmed to calculate at least one anatomical characteristic based on a characteristic of at least one of the reflection of light.

Abstract: A first core layer and a second core layer, serving as optical waveguides, whose refractive indexes are greater than that of a substrate are placed on the surface of the substrate that functions as a cladding layer. An interval between the first core layer and the second core layer is partially narrowed so that lightwaves progressing through these core layers may develop an optical mode coupling. Disposed in this optical mode coupling area is a detector, which comes in contact with liquid or gas and interacts with a substance to be detected, such as chemical or biological substance. A receptor material which selectively captures the substance to be detected is fixed on a surface of the detector. Antibody, enzyme, cell, ionophore, single-strand DNA and the like are examples of the receptor material.

Abstract: Plasmons on a waveguide may deliver energy to photocatalyze a reaction. The waveguide or other energy carrier may be configured to carry electromagnetic energy and generate plasmon energy at one or more locations proximate to the waveguide, where the plasmon energy may react chemically with a medium or interaction material.

Abstract: An optical fiber extends down hole from an OFDR. A first set of sensors with a centrally-located reference reflector is disposed over a first fiber length, and a second set of sensors with a centrally-located reference reflector is disposed over a second fiber length. The sensors of the first and second sensing lengths are positioned at slightly offset positions from the reference reflectors so as to interleave the reflected signals. Additional sensing lengths may be similarly interleaved. The system is used by sending an optical signal along the optical fiber, detecting a reflected optical signal, separating the optical signal into component signals, and extrapolating a well condition therefrom. Another method includes creating a low frequency signal component in a reflected optical signal by placing at least one sensor beyond a Nyquist sampling distance limit, detecting the low frequency signal component, and extrapolating a well condition therefrom.

Abstract: A vibration sensing device, an acceleration sensing system and a method of manufacturing a vibration sensing device wherein the vibration sensing device comprises a flexible disk that is mounted symmetrically about a radial plane and has a mass located on the disk substantially symmetrical about this radial plane which exerts a force that is greater towards the edge than it is towards the centre of the disk. The vibration sensing device is sensitive to on-axis signals and insensitive to cross axis signals.

Abstract: System for scanning a surface, including a light source producing an illuminating light beam; an objective lens assembly, located between the light source and the surface; at least one light detector; an apodizator located between the light source and the objective lens assembly; and a relay lens assembly located between the apodizator and the objective lens assembly, wherein the light source produces an image of the illuminating light beam on the apodizator, the apodizator blocks at least a portion of the illuminating light beam, the relay lens assembly images the blocked illuminating light beam at an entrance pupil of the objective lens assembly, and wherein at least one of said at least one light detector, detects light reflected from said surface.

Abstract: A method and a measurement setup for determination of optical properties of a device under test in both directions in transmission and in reflection, includes a coding device distinguishably coding at least two parts of a provided measurement signal, feeding elements feeding the at least two parts into the DUT from both directions, receiving elements receiving the signals from both directions transmitted and reflected by the DUT, identifying at least the coded parts in the signals transmitted and reflected by the DUT, and analyzing at least the identified parts to determine at least one optical property of the DUT from both directions in transmission and in reflection.

Abstract: A fiber optics differential pressure transducer (100, 200, 300, 400) containing Bragg networks (118), said transducer being used to measure the differential pressure in a Venturi installed inside a pipe (1), through which a fluid like oil is displaced. The transducer comprises a body (110, 230, 360, 410) of different geometries and a diaphragm (2), at least one Bragg network (118) being attached on each of the surfaces of the same. The diaphragm (2) is placed parallel or transversal to the transducer's body (100, 200, 300, 400). The transducer (200) is isolated from the process fluid by flexible mechanical seals (201) which transmit the pressure up to surfaces of the diaphragm (2). The transducer (300, 400) is provided with two relief microvalves for the purpose of protecting the sensor [diaphragms (2)] in overpressure events.

Abstract: A damage detection system including: a optical fiber sensor including a core portion to have a grating portion formed therein, the grating portion having gratings reflecting light, wherein a wavelength band of the reflected light changes when a distance between adjacent gratings changes; a light source to input broadband light into the core portion; two optical filters connected to an output end of the sensor; and an apparatus to perform arithmetic processing on output values of the optical filters, wherein each passband of the optical filters overlaps with the vibration range of the wavelength band, in which a center wavelength of one of the passbands is fixed to an upper area of a vibration center of a center wavelength of the reflected light and that of the other of the passbands is fixed to a lower area thereof.

Abstract: An optical power converting apparatus is provided that may be used with remote sensors. A plurality of remote sensors may be coupled to a backbone optical fiber with each sensor having an optical power converter that receives an optical signal from a head end of that fiber. The optical power converters may store electrical energy derived from that optical signal and use that energy to power the remote sensors. The head end's optical signal may also include a clock signal, and each remote sensor may be set to sense a measurable parameter after a given number of clock cycles have been counted. In a further example, each of the optical sensors may be synchronized before counting these clock signals via a synchronization signal from the optical power converter. The remote sensors may individually and separately uplink their sensed data to the head end on the optical fiber. The apparatus may be implemented in a vehicle health management system, for example.

Abstract: An optically-powered integrated microstructure pressure sensing system for sensing pressure within a cavity. the pressure sensing system comprises a pressure sensor having an optical resonant structure subject to the pressure within the cavity and having physical properties changing due to changing pressures within the cavity. A substrate supports the optical resonant structure. An input optical pathway evanescently couples light into the optical resonant structure. An output optical pathway collects light from the optical resonance structure. A light source delivers a known light input into the input optical pathway whereby the known light input is evanescently coupled into the optical resonant structure by the input optical pathway and a portion of such light is collected from the optical resonant structure by the output optical pathway.

Abstract: Accelerometers for determining acceleration and methods of fabricating an accelerometer are disclosed. In one embodiment, the accelerometer includes a frame, a mass movably suspended on the frame, a fixed element having a rounded surface that does not move with respect to the frame, a movable element having a rounded surface that moves with the mass, and a sensing coil of optical waveguide wrapped around the rounded surfaces to detect movement of the mass in response to acceleration based on interferometric sensing of a change in length of the sensing coil. A method of fabricating the accelerometer includes suspending the mass in the frame and wrapping the optical waveguide around the rounded surfaces. Sensitivity and low fabrication cost of the accelerometers enables their use for integration within an ocean bottom seismic cable. Further, the accelerometer may be an in-line or a cross-line accelerometer depending on the arrangement within the frame.

Abstract: A novel fiber ringdown (FRP) pressure sensor is provided for measuring extremely high pressures under extreme environmental conditions of cold and heat. Pressure measurements are achieved in a time domain by measuring ringdown times of emitted light through the fiber optic loop of the device. The novel FRP sensor can include a light source, such as a diode laser light source, two 2×1 fiber couplers, a section of fused silica single mode fiber, a photodetector, and an electronic control. The novel FRP sensor's performance in the areas of stability, reproducibility, dynamic range, and temperature tolerance are far above those of conventional sensors.

Abstract: An optical sensor has: a sensing portion having an optical fiber to be disposed at a measurement point of temperature, distortion, pressure etc.; a light source to output a light to the sensing portion; and a photodetector to detect a backscattered light from the sensing portion. The sensing portion has a tape sheet and the optical fiber shaped into a corrugated form with a predetermined curvature. Alternatively, the sensing portion has a polymer optical waveguide with a core shaped into a corrugated form with a predetermined curvature.

Abstract: Provided is a physical quantity measuring method using a Brillouin optical fiber sensor. An optical fiber is set on a structure and a pair of pulse lights having different pulse widths is selected. The pulse lights are sequentially transmitted through the optical fiber to obtain back scattering lights and Brillouin gain spectra. The Brillouin gain spectra are compared to each other to calculate a normalized spectrum and a Brillouin frequency is acquired based on the normalized spectrum. The Brillouin frequency is multiplied by a conversion factor of a corresponding physical quantity of the structure to obtain the physical quantity. Accordingly, a portion of the optical fiber from which a sensing signal can be acquired is shortened to improve spatial resolution.

Abstract: A chemical sensing device comprises a fiber core and a fiber cladding. The fiber core comprises an index-modulated grating region having an apodized profile configured for increasing shedding of light into the fiber cladding, and the fiber cladding of the chemical sensing device is configured for reflecting at least some of the deflected light back towards the fiber core. The sensing device is applicable in methods and systems for sensing chemicals.

Abstract: A security bar providing improved security from breach is obtained with the use of a fiber optic cable longitudinally inserted in a hollowed out cavity thereof. Monitoring of the security bar to identify attempts at breach thereof may be achieved by connecting an optical light source to one end of the fiber optic cable and a light monitoring device (i.e., an optical receiver) at the other end. In this manner, a breach of the security bar is identified when the optical receiver fails to receive the light generated by the optical light source. In one embodiment, an isolator which consists of a material that is soft enough to absorb a potential shock but hard enough to break or splinter if the security bar is substantially deformed (e.g., wood) surrounds the fiber optic cable.

Abstract: The invention describes a sensor array with digital signals transmitted over an optical fiber for seismic exploration systems. The seismic system includes a transducer for providing digital optical data signals and an optical interrogator for collecting the digital data. The transducer provides data from seismic sensors to the optical interrogator by acting on an optical carrier transmitted along the optical fiber. The system is designed to utilize known electromechanical seismic sensors with fiber optic telemetry.

Abstract: A sheet includes an optical fiber extending across at least a portion of its surface to detect nuclear radiation. The sheet can line at least a portion of a shipping container or box. Radiation within or outside the container or box reduces optical transmissibility of the fiber. The fiber integrates the radiation over time and/or over the length of the fiber, making the fiber sensitive to even low-level radiation. Dopants, use of particular wavelengths of light or temperatures or other mechanisms can increase the sensitivity of the optical fiber to radiation. The optical fiber is monitored for a change in its transmissibility. A reduction in the transmissibility, such as to below a threshold, can trigger an alarm, such as an annunciator, or send a message that includes information about the time or the container's contents or location when the radiation is detected to a central location, such as a ship's control room or port notification system.

Abstract: This invention provides a method for controlling production operations using fiber optic devices. An optical fiber carrying fiber-optic sensors is deployed downhole to provide information about downhole conditions. Parameters related to the chemicals being used for surface treatments are measured in real time and on-line, and these measured parameters are used to control the dosage of chemicals into the surface treatment system. The information is also used to control downhole devices that may be a packer, choke, sliding sleeve, perforating device, flow control valve, completion device, an anchor or any other device. Provision is also made for control of secondary recovery operations online using the downhole sensors to monitor the reservoir conditions. The present invention also provides a method of generating motive power in a wellbore utilizing optical energy. This can be done directly or indirectly, e.g., by first producing electrical energy that is then converted to another form of energy.

Abstract: The invention provides a fiber-optic sensing system, utilizing a fiber-grating-based sensor, for a physical parameter, e.g., a pressure or a temperature. Different kinds of fiber-grating-based sensors may be used for this purpose but in-fiber gratings such as Fiber Bragg Grating, Long Period Grating and Surface Corrugated Long Period Fiber Grating are particularly suitable. Due to the small size of the optical fiber and the fact that same fiber acts as the sensing element as well as the signal conducting medium, it is possible to install the sensor in a small diameter needle which is commonly used for medical diagnosis and treatment. As a result, when the fiber-optic sensing system of the invention is used for in-vivo measurement of a biological parameter, such a sensing needle can be used for different in-vivo pressure or temperature sensing applications without causing too much harm and discomfort to the subject tested.

Abstract: Certain exemplary embodiments comprise a system comprising a spatially distributed multimode optical fiber; a pixelated photodetector configured to detect a plurality of optical signals provided from said fiber, a first portion of the optical signals indicative of modal conversion and a second portion of the optical signals indicative of modal interference, a predetermined area of said pixelated photodetector adapted to be illuminated by the first portion of the optical signals; and a signal processing module adapted to decode and interpret a plurality of detected variables related to the optical signals.

Abstract: A flexible instrument includes a flexible member having a proximal portion, an intermediate portion, and a distal portion. At least one optical sensor positioned proximate the proximal portion of the flexible member provides a proximal end position signal indicative of the position of the proximal portion of the flexible member. At least one flexible member sensor positioned proximate one of the other portions of the flexible member provides a second position signal indicative of the position of the other portion of the flexible member.

Abstract: Closely spaced conventional optical fibers are arranged in a grid placed between a first surface and a second surface. A penetrating impact onto the first surface results in a hole of a size proportional to the diameter and velocity of the impacting object. The size and shape of the debris plume that travels between the first and second surfaces is also proportional to the diameter and velocity of the impacting object. If the debris plume is sufficiently energetic, a number of the fibers in the grid are broken. The size and shape of the area defined by the broken fibers can be determined simply by determining which fibers are no longer transmitting light. Analytical methods are then used to relate the extent of the damaged area to the location of an MOD impact, the direction from which the impact occurred, and the size of the impacting object.

Abstract: Certain exemplary embodiments comprise a spatially distributed multimode optical fiber; a photodetector configured to detect optical signals provided from said fiber; a wireless digital module coupled to said photodetector and adapted to wirelessly transmit a wireless signal encoding a plurality of detected variables of the optical signals; a wireless receiver adapted to receive the wireless signal; and a signal processing module coupled to said wireless receiver and adapted to decode and interpret the plurality of detected variables of the optical signals.

Abstract: A light waveguide includes: a light introducing portion for introducing light coming from a light source into a waveguide main body; a light radiating surface for radiating the light introduced through the light introducing portion to the hydrogel side; a light transmitting surface which is disposed opposite to and in parallel to the light radiating surface and through which external light incident from the light radiating surface is transmitted to the exterior; a light separation portion, which provided on a surface in a region ranging from the light introducing portion to the light radiating surface and the light transmitting surface, reflecting only totally reflected components of the light introduced through the light introducing portion; an irregular reflection portion provided on the light transmitting surface to change the reflection angle on the light transmitting surface of the light reflected by the light separation portion; and a mirror portion provided at a position opposite to the light introduci

Abstract: Damage caused to a structural composite material is detected while reduction in the strength thereof is prevented. A damage detection system 10 for a structural composite material includes a vibration application apparatus 20 including: a sheet body 22; a plurality of piezo elements 21 sprinkled throughout and held by the sheet body 22; and wires 23 for the piezo elements 21 provided to the sheet body 22. The damage detection system 10 also includes: a fiber optic sensor 30 which includes a grating portion 33 in a core portion 32 thereof, the grating portion 33 reflecting light of a predetermined wavelength; a light source to perform light irradiation onto the core portion 32; and a characteristic detection unit 42 to detect a characteristic of the light reflected from the grating portion 33.

Abstract: The present invention relates to optical confinements, methods of preparing and methods of using them for analyzing molecules and/or monitoring chemical reactions. The apparatus and methods embodied in the present invention are particularly useful for high-throughout and low-cost single-molecular analysis.

Abstract: A distribution optical fiber sensor system measures distortion and temperature of a structure with a high spatial resolution. The system has an optical fiber on an object to be measured. A light source emits a first pulse light having a pulse width longer than a transient response of an acoustic phonon and a second pulse light after a time interval during which vibration of the acoustic phonon is maintained thereby supplying the pulse lights to the optical fiber. A detector detects scattering gain spectra of a Brillouin-scattered light created in the optical fiber by the second pulse light at intervals corresponding to twice the time obtained by equally dividing the pulse width of the second pulse light. A controlling/calculating unit calculates distortion and/or temperature based on the scattering gain spectra for sections of the optical fiber corresponding to the scattering gain spectra at the respective time intervals.

Abstract: An optical wavelength readout system for application in optical sensing systems is disclosed. The system includes a Master unit including a wavelength swept optical source for launching light into a string of optical sensors, and a detection and processing unit for detecting and processing the light emitted by the source. The system also includes a Slave unit including a light coupling device for coupling light from the light source into the string of sensors and for coupling light reflected from the string of sensors to a detection and processing unit arranged to detect and process the reflected light. The Master unit includes a wavelength reference unit adapted to make a reference signal available to other parts of the sensing system. The reference signal represents a generally exact relation between the wavelength of the light emitted from the source and time.

Abstract: An optical safety edge and control system functions correctly despite changes in ambient conditions and/or deformation of the sensor. The optical safety edge and control system automatically compensates for changes in ambient conditions and/or deformation, thus providing a simple easy to use edge sensor which reduces false responses and system failures.

Abstract: Operation of a power-by-light valve (15) by a source (11) along an optical fibre (13) is monitored by means of optical sensors (14) from which light passes back along fibre (13) to monitoring and processing units (16, 17). The sensors (14) include fibre bragg gratings (41, 43) for detecting differential pressure across diaphragms (42) and for detecting temperature. At the input end, an optical coupler (12) supplies sensor signals to units (16, 17) which can control source (11) via a signal (32).

Abstract: A surface sensing system including at least two sensors located on the end of the same optical fiber. The sensors are configured such that they exhibit resonant frequencies or Q-factors that are distinguishable from each other, where the Q-factor is defined as the resonant frequency divided by the resonance spectrum at full-width half maximum (FWHM). Because the sensors have distinguishable resonant frequencies or Q-factors and are located on the end of the same optical fiber, they can be monitored in parallel with little or no optical interference.

Abstract: Integral fiber optic-based condition sensors detect conditions of a composite structure, e.g., a coated wire assembly so as to detect damage or conditions that may damage the same. Preferably, at least one optical fiber sensor having a plurality of Bragg gratings written into the fiber at spaced-apart locations along its axial length is integrated into the electrical insulator coating of a wire, wire bundle or wiring harness. The fiber optic sensor may thus be employed to measure the environmental loads on the electrical wiring including stresses from bending, axial loading, pinch points, high temperature excursions and chemical damage. The system is capable of detecting and locating transient conditions that might cause damage to a wiring system or permanent changes in state associated with damage events. The residual stress in the electrical insulator coating of a wire, wire bundle, or wiring harness are used to monitor the evolution of damage by wear or chaffing processes.

Abstract: A optical fiber sensor for measuring temperature and/or pressure employs temporally created long period gratings. The gratings may be produced by a periodic change in the refractive index of the fiber along the fiber longitudinal axis caused by periodically spaced compressive and/or expansive forces or by spaced-apart unbalanced forces that cause periodic fiber micro-bending. Pressure and temperature are determined by measuring changes in both the wavelength at which light is coupled from a mode guided by a core to a different mode and an amount of such coupling. The gratings are created intrinsically and extrinsically. Single and multiple core fibers are used.

Abstract: In an optical amplifier of the present invention, a part of an input light output from a transmission path fiber is branched as a monitor light, a frequency component corresponding to a period at which a header area of a framed signal light appears, is extracted, and when a voltage level of a direct-current signal obtained by direct-current converting the frequency component becomes lower than a reference voltage, the input interruption of the signal light is detected, to perform a shut-down control of a pumping light source. Thus, an optical amplifier of low cost capable of suppressing an influence of a noise light while ensuring the immediacy, is provided.

Abstract: The invention relates to a device for detecting the corrosion induced by a medium on a structure. The device comprises a chamber (5) closed by a closing disc (4) made of such a material that the disc becomes permeable to the medium once corroded by the medium, and means for measuring the refractive index of the medium present in the chamber. According to a preferred embodiment, an optical fiber is used to measure the refractive index variation.